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At least 19 recordsLinked to original sources

PubMed1979

Renal and vascular activity of prolactin preparations. Contamination of prolactin preparations with ADH and implications on renal and vascular prolactin research.

Prolactin, as a "broad spectrum hormone", has been described to exert also vascular and renal actions in laboratory animals and in humans. However, prolactin preparations of various species are contaminated with neurohypophysial hormones (ADH, oxytocin) which possess vascular and renal activities. Antisera against ADH, oxytocin and prolactin are rather specific inactivators of the biologic activity of the respective hormone; the oxytocinasevasopressinase system of pregnancy plasma destroys ADH and oxytocin. Incubation-identification procedures with antisera against ADH, oxytocin and prolactin and with pregnancy plasma revealed that changes in blood pressure, urine flow and urinary osmolarity cannot be ascribed to prolactin per se but to the ADH impurity of prolactin preparations. Furthermore, recent metabolic studies in normally hydrated, overhydrate and dehydrated animals and humans have shown that prolactin does not affect renal water and electrolyte excretion. Thus, earlier reports on vascular and renal activity of prolactin in laboratory animals and humans should be viewed with great caution. Elimination of neurohypophysial hormone impurities of prolactin preparations by incubation with either ADH and oxytocin antisera or with pregnancy plasma provides techniques for better assessment of the real biologic effects of the prolactin molecule.

Animals↗

PubMed1976

Prolactin stimulation test with perphenazine: an evaluation of plasma prolactin levels and pituitary secretory activity in the rat.

Many investigations of the regulation of prolactin synthesis and release are based on single plasma prolactin determinations. The purpose of the present experiment was to ascertain whether groups of rats (i.e. young or adult, male or female animals, being either intact, gonadectomized or gonadectomized and treated with oestrone), differing in age and/or endocrine status, will react to a single dose of perphenazine by an acute release of pituitary prolactin in proportion to their initial plasma prolactin levels. No consistent relation existed between the classification of the twelve groups of rats into three categories of basal plasma prolactin levels (i.e. less than 20, 25-50, greater than 125 ng/ml) and their response to perphenazine. Even though all groups showed a highly significant increase of plasma prolactin levels the magnitude of the maximum prolactin response at 30 min varied greatly within the groups of one category and thus was not related to the initial prolactin levels. The effect of 14 days of oestrone treatment in increasing plasma prolactin levels in gonadectomized animals was greatest in young and adult male rats, less in young females and not significant in adult females. The results obtained after perphenazine treatment in the latter group made it clear that the effect of oestrogen treatment on prolactin release can be completely blocked by increasing synthesis and/or release of the prolactin-release inhibiting factor (PIF). Since perphenazine induces decrease of pituitary prolactin and a concomitant increase of plasma prolactin levels through lowered PIF-action, the positive effect of oestrogens on prolactin release (as observed in gonadectomized male and young female rats) apparently is caused by a different mode of action. The implications of these findings for the regulation of prolactin release, as affected by the endocrine status of the rat, is discussed. Moreover, comparison of prolactin lost from the pituitary and gained in the circulation of the experimental animals, with amounts of prolactin that were observed to disappear from plasma during the experiment, provided suggestive evidence that the capacity to synthesize and/or eliminate prolactin, after a sudden provoked release of the hormone, differed among the groups. The rates of synthesis by the pituitary, of release from the pituitary into the circulation as well as of elimination of the hormone from the circulation (equally involved in determing actual plasma levels) are thought, therefore, to be far more important for the elucidation of prolactin regulation than single plasma prolactin determinations.

Animals↗

PubMed1976

Relationship between prolactin secretion and hypothalamic prolactin releasing factor in pregnant and puerperium rats.

The present study attempted to elucidate stimulatory factor(s) in the rat hypothalamus which controls prolactin secretion from the anterior pituitary. Rat serum prolactin was elevated so much in late pregnancy that we prepared the hypothalamic extract of late pregnant rats. Prolactin levels in serum and pituitary by radioimmunoassay. After injection of this extract into a lactating rat 48-60 hr after delivery, the serum prolactin level was elevated significantly one to four hr later and the pituitary prolactin level declined two hr later. On the other hand, the hypothalamic extract of normal female rats prepared in a similar manner inhibited prolactin secretion from the anterior pituitary in the lactating rat as described by other authors. These data indicate that the prolactin releasing factor may consist in the hypothalamus of late pregnant rat, and be predominant over the prolactin inhibiting factor during late pregnancy. Prolactin secretion was also investigated in lactating and non-lactating puerperium rats. Prolactin in serum and pituitary declined with days after delivery in non-lactating rats, but not in lactating rats. The presumed factor for such prolactin release in lactating rats is considered to be the prolactin releasing factor.

Animals↗

PubMed1978

Mammary gland prolactin receptor and pituitary prolactin secretion in lactating mice with different lactational performance.

SHN female mice, a high mammary tumour strain, are superior to SLN, a low mammary tumour strain, in lactational performance. Mammary gland prolactin receptor and pituitary prolactin secretion during lactation were compared between these strains. The binding activity, the number of receptor sites per mg tissue and the association constant were measured by the in vitro incubation of mammary gland slices with 125I-labelled bovine prolactin, and the pituitary and plasma levels of prolactin were assayed by homologous radioimmunoassay. There was only a slight difference between strains in any of the parameters for prolactin receptor and for prolactin secretion on either day 4 or day 9 of the first lactation. Almost all the correlation coefficients between each parameter for prolactin receptor and the pituitary or plasma level of prolactin were not statistically significant. These findings suggest that any parameter for prolactin examined in this study is not always directly indicative of lactational performance and further show that the individual variation in the pituitary prolactin secretion during lactation is not so great as to alter the prolactin receptor.

Animals↗

PubMed1976

A possible role of cyclic AMP in mediating the effects of thyrotropin-releasing hormone on prolactin release and on prolactin and growth hormone synthesis in pituitary cells in culture.

Thyrotropin-releasing hormone (TRH) has 3 effects on clonal strains of rat pituitary cells in culture (GH-cells). Two long-term effects of TRH on GH-cells, which are measurable after 3 h or longer, have been previously reported; these are an increase in prolactin synthesis and a decrease in growth hormone production. We report here that TRH also stimulates the rapid release of stored intracellular prolactin. We have investigated the role of cyclic AMP as a possible mediator of the effects of TRH on GH-cells. Cyclic AMP concentrations are higher in cells treated with TRH compared with paired controls; a maximum difference of greater than 150% of control values is detected at 15 min if the incubation is performed in serum-free medium in the presence of 1 mM theophylline. The concentration of TRH required to give half-maximum increases in both prolactin release and cyclic AMP accumulation is 0.3 nM; half-maximal increases in prolactin synthesis occur at 3 nM TRH. Exogenous cyclic AMP (1 mM) causes only a slight increase in prolactin release; 8-bromo-cyclic AMP and 8-methylthio-cyclic AMP (1 mM) do not cause significant release. Phosphodiesterase inhibitors (0.3 mM theophylline, 0.03 mM isobutyl-methylxanthine) increase prolactin release but their effects on hormone synthesis are more complicated. Isobutylmethylxanthine, 8-bromo-cyclic AMP and 8-methylthio-cyclic AMP (0.4 MM) increase prolactin synthesis, but do not significantly affect growth hormone synthesis. Theophylline increases the synthesis of both hormones. Dibutyryl cyclic AMP (0.5 mM or more) increases prolactin release and both growth hormone and prolactin synthesis, but equivalent amounts of sodium butyrate have the same effects. We conclude that in GH-cells under carefully defined experimental conditions: 1) TRH causes an increase in intracellular cyclic AMP concentrations; 2) the increase in endogenous cyclic AMP and the effects of phosphodiesterase inhibitors are consistent with a model with cyclic AMP as a mediator of the effects of TRH on prolactin release; however, they do not prove this model, because the interpretation of these results depends on assumptions which may not all be valid; and 3) none of the analogs of cyclic AMP or the phosphodiesterase inhibitors tested mimic the decrease in growth hormone production caused by TRH.

Animals↗

PubMed1976

Cerebrospinal fluid prolactin: a reflection of abnormal prolactin secretion in patients with pituitary tumors.

Cerebrospinal fluid prolactin levels were determined in 33 patients with pituitary disease, 3 pregnant women at term and 30 control subjects. Prolactin which was immunologically similar to the human prolactin standard was detected by radioimmunoassay in the CSF of most of these subjects. Elevated serum and CSF PRL concentrations were found in three pregnant subjects and in twelve patients with putuitary tumors. Ten patients with pituitary tumors had serum PRL concentrations greater than their corresponding CSF PRL levels. A significant correlation was noted between the elevated serum and CSF prolactin levels in the twelve hyperprolactinemic patients which suggested that the CSF prolactin concentration was influenced by the serum PRL level. Two patients with pituitary tumor however, had CSF prolactin concentrations higher than their serum levels, which suggested that direct secretion of prolactin from the tumor to the CSF can also occur. Three patients with chromophobe adenomas had normal serum PRL concentrations and elevated CSF prolactin levels which differentiated them from fifteen patients with the primary empty sella syndrome who had normal serum and CSF prolactin levels. The finding of normal CSF prolactin levels in the primary empty sella patients argues against the postulate that the diaphragma sellae significantly influences CSF pituitary peptide concentrations.

Acromegaly↗

PubMed1976

Cyclic activity of the pituitary prolactin cells and plasma prolactin levels in the oestrous cycle of the ewe.

The relative proportions of prolactin cells, somatotrophs and gonadotrophs were determined in the adenohypophyses of 28 Merino ewes on selected days during the oestrous cycle. Plasma prolactin levels were measured in 16 of the animals at 3-hr intervals during the 24 hr before autopsy. From Days 1 to 5 of the cycle (Day 0=day of ovulation), plasma prolactin levels were 20-40 ng/ml and the prolactin cells were filled with granules. Plasma levels increased to 168 ng/ml between Days 6 and 9, and marked degranulation of the prolactin cells occurred. The greatest degranulation was found on Days 16 and 0, and was associated with a prolactin surge to a concentration of 610 ng/ml. The rise in plasma prolactin and intensive degranulation of prolactin cells at the time of ovulation and formation of the CL suggest that prolactin is important at this stage of the oestrous cycle.

Animals↗

PubMed1976

Effect of prolactin and growth hormone on prolactin and LH receptors in the dwarf mouse.

Dwarf mice (DW/J;dw/dw) which exhibit a deficiency of prolactin and GH secretion were treated for 8 days with ovine prolactin and/or human GH (10 or 20 mug/day) and the effect on hepatic and testicular prolactin receptors was investigated. In both sexes there was a significant increase in body weight after all hormone treatments, but an increment in testicular weight was observed only after prolactin administration. Prolactin treatment increased the specific binding % of prolactin in liver membranes in females but not males, and in testicular homogenates (together with an increase in LH receptors). The results suggest that lack of prolactin but not of GH retards sexual development in these mice. Treatment with prolactin partly counteracts this deficiency, and the effect may be mediated by the induction of hepatic and testicular prolactin and LH receptors.

Animals↗

PubMedDate not supplied

Effect of the association time of in vivo bound prolactin on the [125I]prolactin receptor assays of female rat livers.

Significantly (P less than 0.01) reduced 125I-labeled ovine prolactin binding (mean, --22%), as a result of an ether anesthesia-reduced rise in serum prolactin, was observed in plasma membrane preparations of liver samples of female rats taken after 5 min of etherization when compared to samples taken from the same animals during the first minute of etherization. This reduction in assayable receptors occurred after 1 h but not 2 h of assay incubation time. Significantly (P less than 0.05) reduced 125I-labeled ovine prolactin binding (mean, --16%) was also observed in liver samples exposed to a 30-min ether-induced rise in serum prolactin when compared to liver samples taken during the first minute of etherization. In contrast, this reduction was apparent at assay incubation times of 1, 2 and 4 h but not at 10 h. These results suggest that serum prolactin can bind to prolactin receptors in vivo and partially block subsequent 125I-labeled ovine prolactin receptor assay. In addition, these data provide evidence that a complex time-dependent binding of prolactin may occur in the plasma of the female rat liver.

Animals↗

PubMed1976

Effects of intraventricular 6-hydroxydopamine injections on serum prolactin and LH levels: absence of stress-induced pituitary prolactin release.

The drug 6-hydroxydopamine (6-OHDA) has been reported to reduce hypothalamic norepinephrine (NE) content after administration into the lateral ventricle without altering the dopamine content of tubero-infundibular neurons. Serum prolactin levels in male rats injected with 2 X 250 mug 6-OHDA were significantly higher than in untreated control rats. Intraventricular injection of male rats with artificial cerebrospinal fluid resulted in elevated mean prolactin levels similar to those observed in 6-OHDA-treated animals. Further experimentation on animals decapitated at different times after removal from the animal quarters, indicates that prolcatin levels in 6-OHDA-treated rats are continuously elevated whereas they rise from basal levels to extremely high levels in CSF-treated rats, thus resulting in similar mean values. The CSF-treated controls ate hypersensitive to the stress of being removed from their normal environment. Such an effect was not observed in 6-OHDA-treated nor in untreated, and thus stress-inexperienced rats. In a long term study, serum prolactin and luteinizing hormone (LH) levels were followed over a period of 71 days after 6-OHDA treatment. Prolactin levels increased within one day after treatment and stayed at a high level for 15 days. Subnormal prolactin values were measured 37 days after 6-OHDA treatment. Serum LH levels were below normal 3 h and one day and were increased 37 and 71 days after 6-OHDA treatment. These results suggest that NE is important in the transmission of stressful stimuli to hypothalamic prolactin regulating centers. They further suggest functional recovery of LH and prolactin regulating mechanisms after 6-OHDA treatment.

Animals↗

PubMed1979

Prolactin-secreting pituitary adenomas in women. II. Menstrual function, pituitary reserves, and prolactin production following microsurgical removal.

A prospective study of 46 women with prolactin-secreting pituitary adenomas and amenorrhea and/or galactorrhea was performed to determine the influence of the selective transsphenoidal removal of these tumors on pituitary and reproductive function. This procedure was effective in restoring menstrual function in 34 of 41 women and in eliminating lactation in 30 of 40 women. Tumor size and preoperative serum prolactin concentrations were the most important factors in predicting the postoperative disappearance of symptoms. Normal menstrual function returned in 33 of 34 women with tumors less than 2 cm in diameter but in only one of seven women with tumors greater than 2 cm. Similarly, galactorrhea disappeared in 29 of 34 women with tumors less than 2 cm but in only one of six women with larger tumors. Menses returned in 31 of 32 women and galactorrhea disappeared in 25 of 31 women with preoperative serum prolactin levels below 200 ng/ml; conversely, menses returned in only three of nine women and lactation ceased in one of six women with preoperative serum prolactin concentrations above 200 ng/ml. Prolactin concentrations decreased in 42 of 43 patients following the removal of pituitary adenomas and returned to normal in 30. Postoperative pituitary reserves of adrenocorticotropic hormone, growth hormone, luteinizing hormone, and follicle-stimulating hormone were normal in most patients. These data indicate that the removal of prolactin-secreting pituitary adenomas by a neurosurgeon accomplished in this surgical technique is effective in restoring menstrual function and eliminating lactation in most women, especially if the tumor is less than 2 cm in diameter and the preoperative serum prolactin concentration is less than 200 ng/ml.

Adenoma↗

PubMed1976

Comparative immunological studies between canine prolactin and prolactin from other species.

Canine pituitary extracts contained material which was capable of inhibiting the binding between antisera to different prolactins and labelled non-canine prolactins. Maximum inhibition of binding was observed in the system consisting of antisera to ovine prolactin and labelled rat prolactin. This system was used to investigate the immunological activity of canine pituitary extracts and partially purified fractions. A rabbit antiserum which was raised against a canine pituitary extract and had significant immunological activity in the above system, together with labelled rat prolactin, was used to develop an assay capable of detecting material in canine pituitary extracts. This material gave parallel dose-response curves to a canine prolactin-rich fraction, D864C and purified ovine and bovine prolactin.

Animals↗

PubMed1978

Prolactin cell adenomas of the human pituitary. Morphologic features of prolactin cells in the nontumorous portions of the anterior lobe.

Twenty pituitary glands, harbouring prolactin cell adenomas, obtained from autopsy of male and female patients of various ages and dying of different diseases have been investigated by the immunoperoxidase technique in order to reveal the morphologic changes of prolactin cells in the nontumorous protions of the anterior lobes. For comparison, 40 nontumorous pituitary glands and 20 pituitaries lodging adenomas not consisting of prolactin cells have also been studied. In all four prolactin cell adenoma cases, the anterior lobes contained numberous prolactin cells outside the tumors, indicating a lack of involution of prolactin cells in the nontumorous portions of the pituitary glands.

Adenoma↗

PubMed1979

International Reference Preparation of human prolactin for immunoassay: definition of the International Unit, report of a collaborative study and comparison of estimates of human prolactin made in various laboratories.

As authorized by the World Health Organization 29th Expert Committee on Biological Standardization, the preparation of human prolactin in ampoules coded 75/504 has been established as the International Reference Preparation (IRP) of human prolactin for immunoassay. From the results of a collaborative study, to which 15 laboratories in nine countries contributed, with the agreement of the participants, the content of each ampoule is defined as 0.650 International Units (i.u.; 650 mi.u.) immunoassay. The results of this collaborative study show that the IRP is adequately stable and suitable for use as a standard for the determination of prolactin in human plasma and serum. Estimates of the prolactin content of human plasma and serum made in the various laboratories have been compared and show good agreement in ranking order, but only fair agreement in the numerical value of the estimates. Numerical agreement is poor between estimates of the human prolactin content of two samples identical except for coding; this shows the difficulty in achieving continuity of estimates when any laboratory calibrates a replacement standard.

Female↗

PubMed1976

Effect of prolactin and the anit-prolactin bromocriptin on the testosterone uptake and metabolism in androgen-sensitive and insensitive canine organs.

Prolactin promotes the growth and function of the prostate in low doses, whereas high doses or previous castration reduce this effect. The antiprolactin bromocriptin should reverse the prolactin action. In the castrated dog the highest accumulation of H3-testosterone given i.v. occurred in the prostate as compared with muscle, urethra, penis, liver and kidney. Prolactin pretreatment increased the radiosteroid uptake only in the liver. Converseley, bromocriptin suppressed the tracer incorporation into the liver, but increased prostatic accumulation. The highest testerone reduction occurred in the prostate of the untreated castrated dogs as compared with other organs. Prolactin suppressed 5 alpha -dihydrotestosterone formation but otherwise did not significantly influence testosterone turnover. Bromocriptin, however, stimulated dihydrotestosterone formation in the prostate and caused complete inhibition of hepatic testosterone reduction.

Animals↗

PubMed1976

Prolactin in amniotic fluid: its correlation with maternal plasma prolactin.

Prolactin concentrations in amniotic fluid from 319 women with normal pregnancies and 29 women with complicated pregnancies were determined by radioimmunoassay. Prolactin levels varied from 36 ng/ml to 1800 ng/ml mean +/- S.D. = 408 +/- 297) in the normal pregnancy group but showed no definite pattern of rise or fall during pregnancy. No difference in levels was found in complicated pregnancies. Prolactin concentrations in the plasma from 203 of these women were also assayed. The levels in the amniotic fluid were about 9 fold higher than those in the plasma. There was no significant correlation between amniotic fluid and plasma levels of prolactin.

Amniotic Fluid↗

PubMed1977

Dopamine enhances the action of prolactin on rat blood vessels. Implications for dopamine effects on plasma prolactin.

It has been claimed that dopamine enhances peripheral uptake of prolactin. Dopamine at 2.1 x 10(-9)M, a concentration which had no effect by itself, enhanced both the potentiation of rat mesenteric vascular reactivity caused by 50ng/ml ovine prolactin and the inhibition of reactivity caused by 500ng/ml prolactin. These observations are consistent with the proposal that dopamine can interact peripherally with prolactin.

Animals↗

PubMed1976

Studies of maternal plasma prolactin and amniotic fluid prolactin. Effects of chlorpromazine and prostaglandin F2alpha.

We have studied the effect of chlorpromazine and PGF2alpha on the blood and amniotic fluid levels of prolactin over a 1-hour period of time in women who were in the 14th-20th week of gestation. Following intramuscular injection of chlorpromazine, maternal plasma prolactin rose 1.0- to 2.5-fold. No significant change was noted in maternal plasma after PGF2alpha administration. Amniotic fluid prolactin declined by 6 to 56%. These changes may be dilutional.

Amniotic Fluid↗