Biomedical subjects

H Jarry

Publications and source records attributed to H Jarry.

At least 91 records · Page 5Linked to original sources

PubMed1992

Indirect evidence to suggest that prolactin mediates the adrenal action of haloperidol to stimulate aldosterone and corticosterone secretion in rats.

The effect of dopamine-antagonists on steroid secretion has revealed conflicting results regarding the confirmation of in vivo findings in vitro. In order to discriminate in vivo systemic and local action of the dopamine-antagonist haloperidol (HAL) on aldosterone and corticosterone secretion, microdialysis of the adrenal cortex in conscious, freely moving rats was employed. The effects of 2.5 mg HAL ip or intraadrenal dialysis of 20 micrograms/ml HAL in rats with an intact pituitary gland on PRL, aldosterone, and corticosterone secretion were examined. Systemic HAL application resulted in a 40-fold increase in PRL secretion and stimulated aldosterone and corticosterone production significantly. In contrast, intraadrenal dialysis of HAL had no effect on the secretory pattern of PRL or either steroid hormone, indicating no direct drug action on cells of the rat adrenal cortex. Similarly, ip injection of 2.5 mg HAL in hypophysectomized rats did not alter PRL or steroid hormone levels. We conclude that the dopamine-antagonist HAL stimulates aldosterone and corticosterone secretion in rats through a pituitary factor, probably PRL, but not through direct effects at the adrenal cortex.

Adrenal Cortex↗

PubMed1992

Paracrine actions of oxytocin, prostaglandin F2 alpha, and estradiol within the human corpus luteum.

Human luteal cells are known to interact in an auto- and paracrine fashion using a variety of substances, including prostaglandins (PGs), steroids, and peptides. In cultures of dispersed luteal cells obtained from several animal species prostaglandin F2 alpha (PGF2 alpha) and oxytocin (OXT) inhibit progesterone (P) secretion, indicating a luteolytic effect of these substances. The disadvantage of luteal cell cultures is that the different luteal cell types do not communicate with each other, i.e. auto- and paracrine effects cannot be studied. Therefore, we used a microdialysis tubing, which is implanted in human corpora lutea (CL) kept under short term organ culture conditions. Ringer's solution is pumped through the dialysis tubing, and substances secreted by the luteal tissue can be determined in the effluent fractions. This system also allows topical application of substances with putative intraluteal effects. In the present report we used PGF2 alpha, OXT, and estradiol (E2) to examine the effects of these substances on the respective other hormones and on P release from young human CL. Intraluteal application of PGF2 alpha stimulated OXT, E2, and P release. OXT was stimulatory to E2 and P secretion, an effect that can be blocked by a specific OXT antagonist and by tamoxifen. Elevation of intraluteal E2 concentrations also had marked stimulatory effects on P secretion. From luteal cell culture experiments it is known that PGF2 alpha and OXT have direct inhibitory effects on P production, but both substances stimulate E2 release. It was also shown that E2 counteracts the inhibitory effects on P release. Therefore, the PGF2 alpha- and OXT-induced E2 release may be responsible for the increased P release. This assumption is further substantiated by the observation that intraluteally applied E2 stimulates P secretion, and preexposure of human CL to tamoxifen prevents the OXT-induced stimulation of P, but not E2, secretion. We conclude that in young human CL, PGF2 alpha and OXT have dual effects: direct inhibitory effects on P release and E2-mediated stimulatory effects, which in young CL result in a net stimulation of P secretion.

Chorionic Gonadotropin↗

PubMed1991

LH release in ovariectomized rats is maintained without noradrenergic neurotransmission in the preoptic/anterior hypothalamic area: extreme functional plasticity of the GnRH pulse generator.

Norepinephrine (NE) in the preoptic/anterior hypothalamic area (PO/AH) is known to be involved in the regulation of luteinizing hormone (LH) secretion. The effects of selective and complete depletion of NE in the PO/AH of ovariectomized (ovx) rats on LH secretion were studied. PO/AH concentrations of NE were reduced by 90% within 6 h and were undetectable (more than 98% depletion) 52 h after bilateral stereotaxic microinjections of 50 micrograms of 5-amino-2,4-dihydroxy-alpha-methylphenylethylamine (5-ADMP). LH levels in the blood were significantly reduced within 60 min after NE depletion but remained low only for several hours. Despite continuously low preoptic NE concentrations episodic LH secretion reoccurred within 4-6 h such that normal blood LH levels were present 6 and 52 h after selective NE depletion. While the alpha 1-adrenoreceptor antagonist prazosin was inhibitory to LH secretion in control rats the drug was totally ineffective in the NE depleted animals. NE may be inhibitory to LH secretion via a beta-adrenergic receptor mechanism. It was therefore also tested whether 5-ADMP causes a massive NE release which might be inhibitory to LH secretion. Propranolol (PROP), a beta-adrenoreceptor blocking drug, was given 30 min prior to preoptic injection of 5-ADMP. Blockade of beta-receptors did not prevent the transient inhibition of LH release. These results indicate that under physiologic conditions the GnRH pulse generator functions only properly when NE is present in the PO/AH and that the stimulatory effect of NE is mediated via an alpha 1-adrenoreceptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Effects of extracts from Cimicifuga racemosa on gonadotropin release in menopausal women and ovariectomized rats.

Remifemin is an ethanolic extract of the rhizome of Cimicifuga racemosa (C.r.) and is used to relieve climacteric hot flushes. In the present study the effects of this preparation on LH and FSH secretion of menopausal women were investigated. After an 8 weeks treatment, LH but not FSH levels were significantly reduced in patients receiving the Cimicifuga extract. To further characterize the endocrinologically active principles of this plant extract, a lipophilic extract of C.r. was prepared and subjected to Sephadex chromatography. Fractions obtained were tested for their ability to reduce LH secretion in ovariectomized (ovx) rats and to compete in vitro with 17 beta-estradiol for estrogen receptor binding sites. Three types of endocrinologically active compounds were obtained: (1) Constituents which were not ligands for the estrogen receptor but suppress LH release after chronic treatment, (2) constituents binding to the estrogen receptor and also suppressing LH release, and (3) compounds which are ligands for the estrogen receptor but without an effect of LH release. It is concluded that the LH suppressive effect of C.r. extracts observed in menopausal women and ovx rats is caused by at least three different synergistically acting compounds.

Animals↗

PubMed1991

Morphological and hormonal changes following vasectomy in rats, suggesting a functional role for Leydig-cell associated macrophages.

The effects of bilateral vasectomy on hormone serum levels as well as Leydig cell and associated macrophage structure were analysed in parallel in rats 36 weeks following the operation. Serum testosterone was decreased in vasectomized rats (1.96 +/- 0.11 ng/ml) compared with control animals (3.44 +/- 0.22 ng/ml, p less than 0.05). Vasectomy also resulted in an increase in serum luteinizing hormone (LH) to 0.299 +/- 0.02 ng/ml compared to the control group (0.175 +/- 0.01 ng/ml, p less than 0.05). Also serum follicle-stimulating hormone (FSH) was increased following vasectomy (350.88 +/- 15.5 ng/ml) compared to 132.0 +/- 4.8 ng/ml in control animals (p less than 0.01). Morphometric analysis of Leydig cells showed hypertrophy with a 19% increase of total cell area, p less than 0.01 (cytoplasm 28%, nucleus 8% increase). On the ultrastructural level, leydig cells demonstrated massively dilated smooth endoplasmic reticulum characteristic for stimulated cells. There was also a significant hypertrophy of the Leydig cell-associated macrophages. The macrophage cell area was enlarged by 22%, p less than 0.01 (cytoplasm 25%, nucleus 18%). Vasectomy also led to remarkable ultrastructural changes of macrophages with a marked dilated and extended rough endoplasmic reticulum. Macrophages were found in apposition to Leydig cells with close cellular contact zones, and they frequently formed cell extensions on Leydig cells. Our data obtained following vasectomy indicate that, by their close contacts to Leydig cells, as well as the known influence on Leydig-cell steroidogenesis, macrophages may form the basis of a local immunoendocrine regulation of the pituitary-gonadal axis.

Animals↗

PubMed1991

Effects of growth factors and hormones on basal and FSH-stimulated inhibin production by porcine granulosa cells in vitro.

The effect of several growth factors, protein and steroid hormones on follicle stimulating hormone (FSH)-stimulated and basal inhibin secretion by mature porcine granulosa cells (g-cells) in culture was examined in order to elucidate the putative role of growth factors and hormones in the regulation of inhibin secretion by porcine g-cells in vitro. Cells were incubated with the respective hormones over a timespan of 0-144 h and immunoreactive inhibin was measured with a radioimmunoassay against porcine inhibin. Epidermal growth factor (EGF) and human transforming growth factor type beta (TGF-beta) decreased basal and gonadotrophin-stimulated inhibin and progesterone in a dose-dependent manner. In the absence of insulin, insulin-like growth factor type I (IGF-I) caused a 4-fold enhancement of basal inhibin secretion, but inhibin secretion was elevated only to 20% above control in the presence of 500 nM insulin. Porcine platelet-derived growth factor (PDGF) had no significant effect on basal or FSH-induced inhibin secretion by g-cells. In addition, neither gonadotrophin-releasing hormone (GnRH) nor prolactin (PRL), arginine vasopressin (AVP) and oxytocin affected basal or FSH-stimulated inhibin release by porcine g-cells. Oestradiol caused a slight but significant (P less than 0.01) rise of basal inhibin production (158% of control) in the last 2 days of culture (96-144 h) and the effect of androstenedione on basal (158% of control) and FSH-stimulated (140% of control) inhibin release (P less than 0.01) was also only visible on Days 4-6 of culture. In contrast to androstenedione and oestradiol, progesterone did not show any effect during 6 days of culture in a dose range of 10(-5) to 10(-9) M. Like steroids, prostaglandin E2 (PGE2) had a stimulatory effect on basal inhibin production (250% of control) by porcine g-cells, visible on Days 3-6 of culture, but an inhibitory effect on FSH-stimulated release (less than 40% of control). Over all the experiments with different hormones and growth factors, tested in varying doses and over a time span of 0-144 h, there was a strong correlation between progesterone and inhibin secretion by g-cells (0-48 h = 0.78; 48-96 h = 0.92; 96-144 h = 0.92). These results suggest that EGF, TGF-beta, IGF-I, oestradiol and androstendione as well as PGE2 have para- and/or autocrine modulatory effects on basal and FSH-stimulated inhibin secretion by mature porcine g-cells in vitro and further demonstrate that the secretion of the proteohormone inhibin and the steroid progesterone are closely related.

Androstenedione↗

PubMed1991

Gamma-aminobutyric acid neurons in the preoptic/anterior hypothalamic area synchronize the phasic activity of the gonadotropin-releasing hormone pulse generator in ovariectomized rats.

To achieve a bolus-type release of gonadotropin-releasing hormone (GnRH) into the portal vessels it is required that GnRH neurons exert phasic and synchronous activity. The activity of GnRH neurons appears to be under an inhibitory influence of the amino acid neurotransmitter gamma-aminobutyric acid (GABA). Preoptic GABA concentrations in ovariectomized (OVX) rats decrease prior to a luteinizing hormone (LH) episode. This reduction of GABAergic activity in the preoptic/anterior hypothalamic area (PO/AH) may be the synchronizing signal for the simultaneous release of GnRH from the hypothalamus. To further study the role of GABA in controlling the GnRH pulse generator we applied GABA, 3-mercaptopropionic acid (MPA) or bicuculline (BIC) locally into the PO/AH by means of push-pull cannulae (PPC). PPC were implanted into the PO/AH of OVX rats and the contralateral, not PPC-implanted PO/AH was lesioned electrochemically. The effects of GABA, MPA or BIC on the GnRH pulse generator were determined by measuring LH levels in blood samples collected in 5-min intervals. Local application of GABA into the PO/AH caused a pronounced reduction of average LH secretion and abolished LH pulsatility. This inhibitory effect was completely reversible. Results of intrapreoptic MPA application on GABA secretion were variable. In only 45% of treated rats MPA caused a reduction of GABA secretion which was associated with a cessation of pulsatile LH release. A pronounced reduction of LH secretion and pulsatility was observed upon local application of the GABA antagonist BIC. Based on these data we propose that oscillating GABA levels in the PO/AH may be the synchronizing signal which triggers bolus release of GnRH into the portal vessels.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Mercaptopropionic Acid↗

PubMed1991

Effects of substance-P and neuropeptide-Y on in vitro steroid release by porcine granulosa and luteal cells.

The presence of substance-P (SP)- and neuropeptide-Y (NPY)-like immunoreactivity was recently shown in nerves that innervate the ovary. In the present in vitro study we demonstrate that both peptides have direct effects on ovarian steroidogenesis. In cultured porcine granulosa (G-) cells, neither peptide affected progesterone (P) production under basal conditions, but they both inhibited gonadotropin-stimulated P secretion. In luteal (L-) cell cultures, basal as well as hCG-stimulated P release were dose-dependently inhibited by NPY (ED50, 4 x 10(-9) M; identical for both, basal and stimulated release), while SP had only a moderate inhibitory effect (ED50, 6 x 10(-8) M). In the presence of AP13, a specific SP antagonist, the inhibitory effect of SP on P release was abolished, which suggests a receptor-mediated effect. In addition, we determined androstenedione (A) and estradiol (E2) release into G- and L-cell culture media. While E2 production in G-cell cultures was not influenced by SP and NPY, both peptides had a dose-dependent stimulatory effect on E2 secretion by L-cells. In contrast to E2 release, A secretion by G- as well as L-cell cultures was increased by gonadotropins. Both SP and NPY decreased gonadotropin-stimulated A secretion by G- and L-cells under basal as well as hCG-stimulated conditions. Furthermore, we demonstrate SP immunoreactivity in media of G- and L-cell cultures with a HPLC retention time identical to that of synthetic SP. This may suggest ovarian synthesis, in which case the peptide exerts auto- and/or paracrine effects on ovarian steroidogenesis. From these in vitro results we suggest that SP and NPY have a modulatory effect on ovarian function in pigs not only by their well known regulatory effects of blood supply, but also by a direct effect on ovarian steroidogenesis.

Androstenedione↗

PubMed1991

Determination of secretion rates of estradiol, progesterone, oxytocin, and angiotensin II from tertiary follicles and freshly formed corpora lutea in freely moving sows.

Two days before ovulation ovarian follicles of sows were implanted with microdialysis systems (MDS) which function like artificial capillaries with exteriorized inlets and outlets. Steroid hormones and paracrine acting factors such as oxytocin (OXT) and angiotensin II (AII) diffuse from ovarian tissue into the fluid, which is pumped through the MDS and collected in fractions. This allows determination of dynamic changes of estradiol (E2), progesterone (P), OXT, and AII secretion during the pre-, peri-, and postovulatory periods in freely moving sows. More than 80% of such implanted follicles ovulate and form competent corpora lutea (CL) allowing continuation of experimentation during the early luteal phase. Follicular E2 release increases before ovulation and decreases with increasing blood LH concentrations. Twenty to 30 h after beginning of the preovulatory LH surge P secretion increases gradually. Both peptides OXT and AII are released episodically by the preovulatory follicle. During the time of decreased E2 and not yet increased P secretion, i.e. during the periovulatory period, mean AII secretion was highest in comparison to the late follicular and early luteal phase. E2 remains measurable during the early luteal phase. OXT and AII were also topically applied into the follicular wall and after ovulation into the CL. AII had no effect on steroidogenesis of both structures. Although OXT was ineffective in the follicle, in young CL it stimulated P secretion. These results indicate that the MDS can be used to study late follicular and early luteal steroid and peptide secretion. The function of OXT and AII in the follicle remains obscure, whereas OXT has a luteotropic effect in young porcine CL.

Angiotensin II↗

PubMed1990

Development and evaluation of an enzyme-linked immunoassay for the prostate: specific antigen utilizing two monoclonal antibodies.

PSA is an important tumor-marker for prostatic cancer disease. We developed a sensitive, simple and inexpensive Sandwich ELISA for PSA with two monoclonal antibodies. The precision and reliability of the assay are reflected in the low inter- and intraassay coefficient of variation. PSA was not detectable in sera from normal females (n = 50). Sera from males with different serum levels of PSA (normal males, patients with prostate hypertrophy, prostate cancer patients, n = 79) and 15 prostate cancer patients treated with Zoladex were measured by our ELISA and by a commercially available RIA. The correlation coefficient between these both test systems was close to 1 (r = 0.97).

Antibodies, Monoclonal↗

PubMed1990

A norepinephrine-dependent mechanism in the preoptic/anterior hypothalamic area but not in the mediobasal hypothalamus is involved in the regulation of the gonadotropin-releasing hormone pulse generator in ovariectomized rats.

Pulsatile gonadotropin secretion from the pituitary is dependent upon the gonadotropin-releasing hormone (Gn-RH) pulse generator producing intermittent release of the neuropeptide into the portal vessels. Various neurotransmitters seem to be involved in the regulation of pulsatile Gn-RH release. The present study was an attempt to determine in vivo the temporal relation of preoptic/anterior hypothalamic area (PO/AH) norepinephrine (NE) release and pulsatile luteinizing hormone (LH) secretion in ovariectomized rats. To assess whether NE acts in the PO/AH to maintain pulsatile Gn-RH release, we applied locally an alpha 1-receptor antagonist into this structure. Push-pull cannulae (PPC) were implanted into the PO/AH of ovariectomized rats. The contralateral, not PPC-implanted PO/AH was lesioned electrochemically. Another group of ovariectomized rats was implanted with a PPC into the mediobasal hypothalamus. Two experiments were performed: (1) To determine whether the PO/AH or the mediobasal hypothalamus is the site where NE exerts its stimulatory effect on LH secretion, we applied doxazosine, a new specific alpha 1-receptor antagonist, locally into these structures by means of PPC. The effect of this adrenergic drug on the Gn-RH pulse generator was examined by measuring blood LH levels. (2) To study the temporal relation between in vivo release rates of NE and amine metabolites in the preoptic area and pulsatile pituitary LH secretion, preoptic perfusates and blood samples were collected at 5-min intervals. Brain perfusates were subjected to high-performance liquid chromatography-electrochemical analysis. In blood samples LH concentrations were determined.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗

PubMed1990

Effects of oxytocin on in vitro steroid release of midstage small and large porcine luteal cells.

Previously, we have demonstrated an inhibitory effect of oxytocin (OXT) on progesterone (P) and androstenedione (A) release of porcine luteal cell cultures. The present study examines whether OXT modulates P, A, or estradiol (E2) release of so-called small luteal cells (SLC) or of granulosa-derived large luteal cells (LLC). To ensure clean Percoll-gradient separation of the 2 cell types, corpora lutea not older than 6 days were used. SLC, but not LLC, responded to human (h)CG (6 ng/ml) with increased P and A, but not E2, release. When OXT was added to the culture system, both basal as well as hCG-stimulated P release of SLC, but not of LLC, were dose dependently reduced. In contrast, E2 production of SLC and LLC was significantly stimulated by OXT whereas A release of SLC cultures, but not of LLC, was inhibited in response to OXT. In the presence of a specific OXT-antagonist, this inhibitory effect of OXT on P release was abolished, indicating a specific receptor-mediated effect of OXT on porcine luteal cells. When E2 was added to the culture medium, a dose-dependent stimulatory effect on P release of SLC was demonstrated. The presence of the E2 receptor antagonist monohydroxy-tamoxifen in the culture system prevented the E2-induced increase of P release of SLC. E2 was able to counteract dose dependently the OXT-induced inhibition of P release in SLC cultures. These results suggest that OXT may have a dual function in young corpora lutea. The reduction of P and A production can be interpreted as a luteolytic effect of OXT. The simultaneous increase of E2 production, however, may also point to an indirect luteotropic effect since E2 was shown to stimulate luteal P release and to counteract OXT-induced inhibition of P release excessively.

Androstenedione↗

PubMed1990

Release and effects of oxytocin on estradiol and progesterone secretion in porcine corpora lutea as measured by an in vivo microdialysis system.

Individual corpora lutea (CL) of Göttinger miniature pigs were implanted with an in vivo microdialysis system. This system functions like an artificial capillary, allowing diffusion of intraluteally secreted substances into the lumen of the dialysis system and administration of hormones into individual CL and simultaneous measurement of the response. After surgery the sows are fully awake and unrestrained. In the present study the in vivo release rates and secretion dynamics of progesterone (P) and oxytocin (OXT) were investigated. The dialysis system was implanted at day 2-4 of the estrous cycle, and dialysis experiments were performed throughout the next 3 days. Fractions were collected at 30 min intervals, and the concentrations of P and OXT were measured by RIA. Three major observations were made: Spontaneous intraluteal secretion of P and OXT occurred in a pulsatile manner. OXT secretion episodes in individual CL often coincide, indicating a simultaneous release from many CL of one ovary but also from the CL located in the contralateral ovary. OXT episodes also often coincide with P pulses; statistical evaluation revealed a significant correlation between P and OXT secretion. Intraluteal application of OXT stimulated luteal P and estradiol (E2) release in a dose-dependent manner. E2 added to the perfusates was also stimulatory to P release. The stimulation of P release by OXT could be antagonized by prior treatment of the CL with tamoxifen. We demonstrate for the first time in vivo the secretion of OXT from porcine CL. The microdialysis system enabled us to collect samples at the site of steroid and peptide release, i.e. within the intact luteal tissue. Our results suggest a stimulatory effect of OXT on P release from young and middle-aged CL and are in marked contrast to the previously demonstrated inhibitory effect of OXT on P release when luteal cells were cultured in vitro. A possible explanation for this apparent discrepancy is that OXT stimulates intraluteal release of E2, which is a powerful P releasing hormone, overcoming the direct inhibitory effect of OXT. This suggestion is substantiated by the observation that E2, when added to the perfusion medium, indeed stimulated P release.

Animals↗

PubMed1989

In vivo demonstration of a paracrine, inhibitory action of Met-enkephalin on adrenomedullary catecholamine release in the rat.

The present study was an attempt to assess the inhibitory effect of methionine-enkephalin (Met-Enk) on adrenal catecholamine release under in vivo conditions employing a microdialysis system. One adrenal gland of intact male rats was implanted with a microdialysis system. One day after surgery, the adrenal dialysis system was connected to a perfusion pump and Ringer solution or a Ringer solution containing Met-Enk, naloxone (Nal), or a combination of Met-Enk and Nal was used for dialysis; dialysate fractions were collected at 5-min intervals. Catecholamine secretion was stimulated by an iv injection of 1.4 mumol (200 micrograms) acetylcholine (Ach). Met-Enk-immunoreactive material in adrenal medulla extracts and dialysate fractions was analyzed by reverse phase HPLC combined with Met-Enk RIA. Under resting conditions, adrenal release rates of norepinephrine and epinephrine into the Ringer solution were constant. After Ach application secretion of both catecholamines increased about 2.7-fold. Within 10 min after the injection, catecholamine levels returned to baseline levels. Intra-adrenal application of Met-Enk reduced Ach-stimulated epinephrine, but not norepinephrine, secretion significantly; application of Nal did not affect Ach-stimulated catecholamine secretion in the initial fraction after Ach injection, but significantly prolonged amine secretion after the cholinergic stimulus. Application of Nal followed by a combined application of Met-Enk and Nal was without an effect on the amount of catecholamines released in the initial fraction after Ach injection compared to that in the control group. Thus, naloxone prevented the inhibitory effect of Met-Enk on Ach-stimulated CA release. HPLC analysis of adrenal medulla extracts followed by Met-Enk RIA revealed that several forms of Met-Enk are present in chromaffin cells, whereas in adrenal dialysates only one, albeit broad, signal of Met-Enk immunoreactivity was detectable. We demonstrate in vivo a paracrine or autocrine action of Met-Enk on Ach-stimulated catecholamine release by applying the peptide directly into the adrenal gland via a microdialysis system. We conclude that neuropeptides endogenous to the adrenal gland not only reduce the amplitude of catecholamine secretion in response to an Ach stimulus but, in addition, modulate the duration of catecholamine secretion. This is demonstrated by a prolonged catecholamine secretion if opiate receptors are blocked by Nal.

Adrenal Medulla↗

PubMed1989

Inhibin production by porcine granulosa and luteal cells: development and biological validation of a RIA.

We describe the development and biological validation of a radioimmunoassay for immuno- and bioactive porcine inhibin. A synthetic 1-32 porcine inhibin peptide was used to raise an antiserum and Tyr-1-32 peptide as tracer. As standard we employed porcine follicular fluid calibrated with the 1-32 alpha-inhibin. Medium obtained from serum-free cultured porcine granulosa cells was chromatographed on Superose S-12 and Mono-Q. Resulting fractions were analysed for inhibin bio- and immunoreactivity. It is shown that granulosa cells produce at least two types of bioactive inhibins, one being also immunoactive in our RIA. We studied secretion of immunoreactive inhibin from porcine ovarian cells under various conditions: Inhibin secretion from mature and immature granulosa cells can be stimulated by FSH, whereas hCG enhances inhibin secretion only from mature granulosa cells. During extended time of culture, the capability of granulosa cells to secrete inhibin is reduced. In contrast, progesterone secretion from these cells increases; this is due to spontaneous functional luteinization. This assumption is supported by the low inhibin secretion of luteal cells in comparison to granulosa cells. Intracellular inhibin content in luteal cells is below detection limit of the RIA, whereas granulosa cells contain readily detectable amounts of this hormone.

Animals↗

PubMed1988

In vivo release rates of substance P in the preoptic/anterior hypothalamic area of ovariectomized and ovariectomized estrogen-primed rats: correlation with luteinizing hormone and prolactin levels.

Push-pull cannulae were implanted into the preoptic/anterior hypothalamic area (POA) of ovariectomized (OVX) rats. After recovery animals were treated with estradiol (E2) or corn oil and they were perfused 3 days later. Substance P (SP) concentrations were measured in 15 min perfusate fractions, blood samples were taken at similar intervals. SP concentration in POA perfusates were readily measurable. Following estrogen priming SP release increased significantly each afternoon prior to the estrogen induced prolactin and luteinizing hormone (LH) surges. No such increase of SP release was observed in OVX rats with constant LH and prolactin levels throughout the day. Mean SP rates in OVX rats were significantly higher in comparison to OVX estrogen-primed rats. These results indicate that SP may be involved in the feedback mechanisms of estrogen on prolactin and LH release. Authenticity of SP in POA perfusates was made probable by high-performance liquid chromatography (HPLC) where synthetic SP eluted at the same retention time as the signal measured in push-pull perfusates.

Animals↗

PubMed1988

Inhibitory effect of oxytocin and vasopressin on steroid release by cultured porcine luteal cells.

Previously, we have demonstrated the presence of substances reacting like arginine vasopressin (AVP) and oxytocin (OXT) in acid extracts of corpora lutea (CL) of pigs by RIA. The present study examined purified extracts of CL by using HPLC. The results of these experiments show that CL of nonpregnant sows contain AVP and OXT. Little is known about possible auto- and paracrine effects of AVP and OXT in the ovary. Therefore, we investigated the influence of AVP and OXT on progesterone, estradiol, and androstenedione secretion in porcine luteal cell cultures from nonpregnant sows. Progesterone and androstenedione secretion increased significantly (P less than 0.05) in the presence of ovine LH (oLH), whereas no change in basal estradiol levels could be observed under the same conditions. When AVP or OXT was added to the culture system a dose-dependent inhibition of basal as well as oLH-stimulated progesterone secretion was measured. Under basal conditions, a dose of 1 pg AVP/ml decreased progesterone secretion significantly (P less than 0.05), but to reach the same effect in the presence of OXT a dose of 100 ng/ml was necessary. In the presence of oLH the addition of as little as 0.01 pg AVP/ml inhibited progesterone secretion significantly (P less than 0.05). On the other hand, 10 ng OXT/ml or higher doses were needed to decrease oLH-stimulated progesterone release. In the presence of specific peptide antagonists the inhibitory effect on progesterone release was abolished. These results suggest that AVP and OXT effects are mediated through specific receptors. OXT and AVP also inhibited androstenedione secretion, but had no effect on estradiol secretion. Calculation of the ED50 data from dose-response curves of both peptides show that AVP is about 10(4)-fold more active than OXT in inhibiting in vitro progesterone and androstenedione secretion. This suggests that AVP as well as OXT may play an important role in the regulation of ovarian function.

Androstenedione↗

PubMed1988

Differential response of substance P-containing subtypes of adrenomedullary cells to different stressors.

Adrenal medullary cells produce not only the catecholamines norepinephrine and epinephrine but also a number of peptides; hence, they can be subclassified according to their peptide quality. The present study was an attempt to test whether different stressors address different subclasses of adrenal medullary cells. The adrenal gland of intact male rats was implanted with a dialysis system, and the jugular vein was catheterized. One day after surgery, the adrenal dialysis system was connected to a perfusion pump, and Ringer solution was used for dialysis; dialysate fractions were collected at 15-min intervals, and blood was withdrawn at the end of each fraction period after a 2-h equilibration period. The basal release rates of pituitary PRL and adrenal corticosterone, measured in plasma, and of epinephrine, norepinephrine, and substance P (SP) measured in the adrenal dialysates, were constant during the preshock period. SP concentrations in the blood were below the detection limit of the RIA. Application of mild electric foot shock stress resulted in a marked increase in adrenal catecholamine and SP release. Plasma PRL and corticosterone levels also rose during the time of exposure to foot shock, but plasma SP concentrations remained at undetectable values. In contrast, a metabolic stress i.e. insulin-induced hypoglycemia, did not affect adrenal SP release, although adrenal catecholamine release increased to a larger degree than after foot shock stress. Plasma PRL and corticosterone levels also increased during insulin-induced hypoglycemia. It is concluded that an exogenous stressor (electric foot shock) activates adrenomedullary cells containing catecholamines and SP, whereas these cells are not activated by the stress of insulin-induced hypoglycemia.

Adrenal Medulla↗