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L Pitzel

Publications and source records attributed to L Pitzel.

35 records · Page 2Linked to original sources
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↗
PubMed1986

Demonstration of mRNAs for oxytocin and prolactin in porcine granulosa and luteal cells. Effects of these hormones on progesterone secretion in vitro.

The relative levels of mRNAs for relaxin, prolactin, inhibin and oxytocin have been measured in porcine granulosa as well as luteal cells by hybridisation to single-stranded synthetic DNA. The likelihood of a paracrine function of oxytocin and prolactin in the porcine ovary was inferred from the in vitro effects of both hormones on progesterone secretion of ovarian cells. Both hormones were found to inhibit progesterone secretion of luteal cells. In contrast, only prolactin but not oxytocin stimulated progesterone secretion in granulosa cells.

Animals↗
PubMed1984

Lack of response in the release of oxytocin and vasopressin from isolated neurohypophyses to dopamine, met-enkephalin and leu-enkephalin.

We investigated the effects of dopamine, met-enkephalin and leu-enkephalin on basal and ouabain-stimulated release of oxytocin and vasopressin from isolated neurointermediate lobes. The present study revealed that neurohypophyseal hormone release was not affected by dopamine, neither from lobes of untreated rats nor from those of rats with dopamine-deficiency (pretreated with alpha-methyl-p-tyrosine-methylester). Likewise, metoclopramide, a dopamine antagonist, was unable to alter the neurohypophyseal hormone release. Our results also indicate that the opioid peptides met-enkephalin and leu-enkephalin do not influence spontaneous or ouabain-stimulated oxytocin and vasopressin release, which is in accordance with our findings that naloxone under our experimental conditions is also ineffective.

Animals↗
PubMed1984

The effect of long-acting ACTH on plasma corticosteroids, testosterone, and LH levels in the male pig.

Intramuscular injection of long-acting ACTH (10 micrograms/kg body weight) into male pigs, fitted with permanently indwelling jugular catheters, resulted in a significant rise of plasma corticosteroid concentrations for a period of between 0.5 and 20 hours after injection. Plasma testosterone levels were significantly increased between 60 and 120 min after ACTH administration. Between 6 and 12 hours after ACTH application, however, they were significantly depressed, evidencing a two phase effect of ACTH on testosterone levels. Plasma LH concentrations showed a slight but progressive decrease which was significant between 2.5 and 12 hours p.i. From these results it has been concluded that long-acting ACTH stimulates testosterone release. Because LH levels were depressed, they cannot have been responsible for the increase in plasma testosterone. The increase of plasma testosterone concentrations was not accompanied by a change of plasma prolactin levels.

Adrenal Cortex Hormones↗
PubMed1984

The stimulatory effect of corticotrophin on testicular testosterone release in male rabbits.

Intravenous injection of 1-24 ACTH synthetic analogue (10 micrograms/kg body weight 1-24 ACTH) via permanent indwelling jugular catheters to intact male rabbits, resulted in a rapid rise of plasma corticosteroid (C) and plasma testosterone (T) levels. Mean C levels were significantly elevated during the period between 10 and 100 min after ACTH administration whereas mean T concentrations showed a significant rise at 20 min after the 1-24 ACTH administration. On the other hand a significant suppression of plasma T levels was observed 120 min p.i., indicating a biphasic effect of 1-24 ACTH on plasma T levels. Castrated animals reacted to 1-24 ACTH with mean C levels, comparable to concentrations in intact rabbits, whereas their lowered plasma T concentrations showed no changes. When 1-24 ACTH was administered to intact animals 96 h after pretreatment with HCG, plasma T levels were significantly elevated at 20 min after 1-24 ACTH injection whereas a second HCG injection was ineffective in modifying T concentrations. From these results we concluded, that exogenously applied 1-24 ACTH can effectively stimulate the testicular T release in adult male rabbits and that such release is independent of the LH receptors in Leydig cells.

Adrenocorticotropic Hormone↗
PubMed1981

Changes in posterior pituitary oxytocin release in vitro during the estrous cycle of female rats.

The in vitro release of oxytocin (OXT) from posterior pituitary lobes (PPL) of adult female rats is linked to the stage of the animals' sexual cycles. After incubation in normal Locke's solution (K+ 5,6 mM), the basal OXT release from the PPL of rats on diestrus 1 and estrus amounted to 2.25 +/- 0.53 ng/lobe/10 min (mean +/- S.E.M.) and 4.71 +/- 0.61 ng/lobe/10 min, respectively. Excess K+ (56 mM/l) in the presence of Ca++ (2.2 mM/l) increased OXT liberation from the PPl of diestrous and estrous rats to 12.41 +/- 2.65 ng/lobe/10 min und 36.33 +/- 6.18 ng/lobe/10 min, respectively. When Ca++ was omitted from the incubation medium, the K+-excess induced OXT release from the PPL of estrous rats decreased to 21.54 +/- 2.65 ng/lobe/10 min whereas no change occurred in the OXT-release from the rats' PPL on diestrus 1 in the presence of Ca++. The results indicate a cycle-dependent release and suggest that OXT plays a role in the reproductive processes.

Animals↗
PubMed1981

Oxytocin release from isolated posterior pituitary lobes of adult male rats as determined by radioimmunoassay.

In vitro oxytocin (OXT) release from isolated posterior pituitary lobes (PPL) of adult male Wistar rats was measured under basal and K+- stimulated conditions using a specific, sensitive radioimmunoassay. A basal release of 0.95 +/- 0.20 ng OXT/lobe/10 min was estimated in standard Locke's bathing solution. An excess of K+ (56 mmol/l) augmented the OXT secretion to 18.1 +/- 2.24 ng OXT/lobe/10 min in the presence of 2.2 mmol/Ca++. A stimulatory effect of K+ excess was also determined in Ca++-free medium and in Ca++ free medium enriched with 0.7 mmol/l EGTA. An inhibitory effect on K+-stimulated OXT release was achieved by raising the Mg++ concentration from 1.0-8.0 mmol/l of bathing fluid. During prolonged K+ stimulation the rate of OXT release declined exponentially. Estimation of the OXT content of PPLs after prolonged stimulation with K+ excess revealed that the lobes still contained 80% of their original OXT content.

Animals↗
PubMed1980

Corticotropin- and lysine-vasopressin induced changes of plasma corticosteroids and testosterone in the adult male pig.

Intravenous injection of 10.0 micrograms/kg body weight synthetic corticotropin (1-24 ACTH) into chronically cannulated boars resulted in significantly elevated plasma corticosteroid and testosterone levels between 20 and 140 min (corticosteroids) and 20--80 min (testosterone) after injection. Administration of lysine-vasopressin (LVP) at doses of 0.1, 0.2 and 0.4 IU/kg body weight elicited a significant increase of plasma corticosteroids between 20 and 40 min after injection; on the other hand, plasma testosterone concentrations tended to fall when compared to pre-treatment levels. From our results it can be concluded that exogenously applied ACTH can effectively stimulate the release of corticosteroids and testosterone. Intravenous administration of LVP results in significantly, although not maximally increased plasma corticosteroid concentrations; the release of endogenous ACTH induced by LVP injection, on the other hand, appeared to be too small to stimulate testosterone release significantly.

Adrenal Cortex Hormones↗
PubMed1979

Effects of an intravenous injection of tetracosactid on plasma corticosteroid and testosterone levels in unstressed male rabbits.

Administration of tetracosactid into male rabbits, fitted with permanently indwelling jugular catheters, resulted in a rapid rise of plasma corticosteroids and plasma testosterone. Corticosteroid concentrations were significantly elevated at 40 and 60 min and testosterone concentrations 20 min after the iv injection of tetracosactid (2.5, 5.0, and 10.0 micrograms/kg body weight), in comparison to pre-treatment levels. Corticosteroid values in plasma were elevated as long as 120 min after tetracosactid injection. In contrast, testosterone levels were lower at 60-120 min after tetracosactid injection than corresponding pre-treatment values. However, these differences were not significant. At the doses used no tetracosactid-dose-dependent corticosteroid or testosterone release could be found; apparently, testosterone release is only dependent upon basal plasma levels but not upon the dose of tetracosactid applied. From these studies it is concluded that tetracosactid may bring about an increase or decrease of testosterone concentration in plasma in the buck depending upon the length of time elapsing between injection of tetracosactid and blood withdrawal.

Adrenal Cortex Hormones↗
PubMed1979

Effect of dexamethasone on plasma concentrations of LH, FSH and testosterone in women with hirsutism.

Thirty sexually mature women with hirsutism were treated with 3 x 1.5 mg dexamethasone per day over a period of three days. Before and after treatment, plasma concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), and testosterone were determined. While an effect of dexamethasone on LH plasma levels could not be established statistically, FSH and testosterone plasma concentrations decreased significantly in comparison to their initial values (p less than 0.01). Special attention is directed to the different effects of dexamethasone on LH and FSH plasma concentrations.

Chorionic Gonadotropin↗
PubMed1977

[Classification and supervision of hyperlipemias (author's transl)].

Different methods for determination and classification systems of serum lipoproteins were used and compared in 300 patients with hyperlipidemia. The procedures and methods were examined to find out which would provide a useful classification for diagnosis and therapy. Lipid electrophoresis on agarose gel gave no reliably reproducible typing. With acetate and polyacetate foils, Type llb was not recognizable in the majority of cases. Neither the determination of beta-cholesterol after polyanion precipitation nor quantitative lipid electrophoresis calculating the values as lipoprotein lipid gave type determinations which completely agreed with the ultracentrifuge, but the best coincidence with the ultracentrifuge was obtained with these two methods. The second method is chiefly suitable for supervision.

Chylomicrons↗
PubMed1975

[Increased estradiol-estrone quotient in rat liver by hydroxysteroids: an effect of the specific hydrogen transfer between steroids].

After addition of estrone to rat liver slices, a quotient of estradiol/estrone of ca. 0.1 is reached within 1 - 2 min. By additional application of 17 beta-hydroxysteroids this quotient is changed in the direction of estradiol, although the applied concentrations of both steroids are far below the concentration of the cytoplasmic redox couple NADH/NAD. Of all the steroids tested, testosterone had the strongest influence on the quotient, especially in the liver of female rats. This influence is smaller in the livers of male rats and infantile animals. The changing of the E2/E1 quotient by testosterone can be inhibited by the antiandrogen cyproteron acetate. Steroids with hydroxy groups at C-3 or C-20 or high concentrations of non-steroids, which can be oxidized by NAD, change the E2/E1 quotient only minimally. The experiments demonstrate that in liver, the redox couple estradiol/estrone is not in equilibrium with the main redox couple of the cytoplasmic NADH/NAD. Only on account of this fact it is possible that relatively low concentrations of testosterone change the E2/E1 quotient via the C-17 leads to C-17 hydrogen transfer between steroids. Biological consequences are discussed.

Animals↗
PubMedDate not supplied

Regulation of steroid production and its function within the corpus luteum.

During the second half of the luteal phase, the human corpus luteum becomes responsive to regular luteinizing hormone (LH) pulses. These LH pulses stimulate progesterone secretion tonically, and during this tonic stimulation, additional LH-independent progesterone pulses occur, which are particularly pronounced in women with human chorionic gonadotropin-stimulated luteal function. No progesterone pulses are seen in women suffering from corpus luteum deficiency due to absent LH pulses. The corpus luteum thus has a progesterone pulse generator turned on by gonadotropins but functioning for several hours without further gonadotropic support. This pulse generator appears to be regulated by intraluteal auto-/paracrine mechanisms, which we have investigated in a porcine model using molecular, cellular, and in vivo tools. Luteal oxytocin and progesterone release occurs in tightly coupled pulses. In vivo, oxytocin and prostaglandin F2 alpha(PGF2 alpha) stimulate estradiol and progesterone release and estradiol itself further stimulates progesterone release. Analysis of the different luteal cell compartments (large luteal cells, small luteal cells, fibroblasts) suggests an intraluteal circuit that involves paracrine effects of estradiol, oxytocin, and PGF2 alpha. At the time of luteolysis, the luteotropic effects of estradiol are inhibited by tumor necrosis factor derived from invading macrophages and the intraluteal circuit is thereby disrupted, leading to luteolysis.

Corpus Luteum↗
PubMedDate not supplied

Multicenter evaluation of the Elecsys CA 125 II assay.

The technical performance and clinical usefulness of the newly developed Elecsys CA 125 II assay (Boehringer Mannheim) was evaluated in a multicenter study. Imprecision studies were carried out using control sera and human pool sera with CA 125 concentrations from 11 to 1026 U/ml. Within-run CVs between 0.7 to 4.8% (median 1.7%) and between-day CVs between 2.4 to 10.9% (median 5.7%) were found. Method comparison studies with Enzymun-Test CA 125 II carried out in four laboratories yielded slopes between 0.94 to 1.07 and intercepts < 3 U/ml. A good comparability of the Elecsys CA 125 II assay was also found with one MEIA and the Centocor" IRMA. For a second MEIA and a second IRMA the slopes were 1.23 and 1.42, and the corresponding correlation coefficients were 0.987 and 0.977, respectively. The Elecys CA 125 II concentrations are clearly related to the tumor stage of ovarian carcinoma patients. The maximum of diagnostic efficiency of ovarian carcinoma patients compared with patients of benign gynecological diseases is reached at 150 U/ml with a specificity of 93% and a sensitivity of 69%. Follow-up studies of ovarian carcinoma patients reflect the status of the disease and the effect of various therapeutic applications. The technical and clinical evaluation of the Elecsys CA 125 II assay show a superior analytical performance with a broad measuring range up to 5000 U/ml and a short measuring time of 18 minutes.

Biomarkers, Tumor↗