Serotonin and acetylcholine affect the release of prolactin and growth hormone from pituitary glands of domestic fowl in vitro in the presence of hypothalamic tissue

Anterior pituitary glands from broiler fowl were incubated alone or with hypothalamic tissue in medium containing either serotonin or serotoninergic drugs, acetylcholine or cholinergic drugs, and the release of prolactin (Prl) and growth hormone (GH) measured by homologous radioimmunoassays. The neurotransmitters and drugs affected the release of hormones from the pituitary gland only when hypothalamic tissue was also present. Serotonin and its agonist quipazine stimulated the release of Prl and inhibited release of GH in a concentration-related manner. The antagonist methysergide blocked the effects of serotonin and quipazine on Prl. Acetylcholine and its agonist pilocarpine also stimulated release of Prl and inhibited release of GH in a concentration-related manner. Atropine blocked these responses. The results show that serotonin and acetylcholine affect pituitary hormone secretion by acting on the hypothalamus. They may stimulate the secretion of a Prl releasing hormone and somatostatin.     

Inhibition by testosterone of prolactin and growth hormone release from chicken anterior pituitary glands in vitro

Pituitary glands and hypothalami from broiler fowl were incubated in medium containing testosterone, and prolactin and GH release were determined. Pituitary glands were also preincubated for 20 h in medium containing testosterone, and then in medium containing various secretagogues. Testosterone inhibited the release of prolactin directly from the pituitary gland in a concentration-related manner. The hypothalamus stimulated the release of prolactin, but by a lesser amount in the presence of testosterone. When pituitary glands were preincubated with testosterone, subsequent release of prolactin was inhibited, except with the highest concentration which stimulated prolactin release. Hypothalamic extract (HE) markedly stimulated prolactin release from control pituitary glands although testosterone-primed glands were less responsive. The stimulation of prolactin release by thyrotrophin releasing hormone (TRH) and prostaglandin E2 (PGE2) was also reduced by preincubation of the pituitary glands with testosterone. Priming with testosterone did not affect the release of GH from pituitary glands alone, but reduced the TRH-, HE- and PGE2-stimulated release of GH. These results demonstrate that testosterone directly inhibits prolactin secretion and reduces the sensitivity of pituitary lactotrophs and somatotrophs to provocative stimuli.     

Oestradiol 17 beta modifies fowl pituitary prolactin and growth hormone secretion in vitro

Chicken pituitary glands were incubated in medium containing oestradiol 17 beta (E2), alone or together with single whole hypothalami. E2 stimulated prolactin release from the pituitary and increased the prolactin releasing activity of the hypothalamus, but did not affect growth hormone release. Preincubation of pituitaries with E2 dramatically stimulated subsequent prolactin release. Pituitaries primed with E2 were more responsive to the prolactin-stimulating effects of hypothalamic extract (HE) and thyrotrophin-releasing hormone (TRH) and more sensitive to the prolactin-inhibiting effect of dopamine. E2-primed pituitaries were much less sensitive to the growth hormone releasing activity of TRH and HE. These results show that E2 may regulate pituitary function by direct effects on hormone release by modifying pituitary sensitivity to stimulatory or inhibitory influences and by altering hypothalamic releasing activity.     

Mechanism of serotonin effects on prolactin and growth hormone secretion in domestic fowl

Brain serotonin levels were increased in immature chickens by ip injection of pargyline (75 mg/kg) and clorgyline (5 mg/kg) and by L-tryptophan (100 mg/kg) and imipramine (10 mg/kg) treatment. These treatments increased the circulating prolactin level and reduced the concentration of plasma growth hormone (GH). Treatment with para-chlorophenylalanine (PCPA, 100 mg/kg) reduced the brain serotonin content and the level of plasma prolactin. Treatment with these drugs in vivo similarly affected the basal level of prolactin release from pituitary glands in vitro, although it did not affect the basal level of GH release. The in vitro responsiveness of the pituitary gland to hypothalamic stimuli eliciting prolactin secretion was increased by in vivo pargyline and combined tryptophan: imipramine treatment but reduced by PCPA administration. The in vitro GH response to hypothalamic stimulation was reduced after the in vivo injection of pargyline, clorgyline and tryptophan: imipramine. The hypothalami from clorgyline and tryptophan: imipramine treated birds induced a greater stimulation of in vitro prolactin secretion from control pituitary glands than hypothalami from controls birds, whereas the GH releasing activity was reduced. These results suggest that serotonin stimulates prolactin secretion in chickens by increasing pituitary responsiveness to hypothalamic releasing factors and by increasing the prolactin releasing activity of the hypothalamus. Serotonin appears to suppress GH secretion by reducing pituitary sensitivity to releasing factors and by reducing hypothalamic GH releasing activity.     

Hypothalamic control of prolactin and growth hormone secretion in the pituitary gland of the pigeon and the chicken: in vitro studies

Hypothalamic extracts stimulated the release of prolactin and growth hormone from pigeon and chicken pituitary glands incubated in vitro. Release of hormone was proportional to the amount of hypothalamic extract added. Pituitary glands from "lactating" pigeons released more prolactin and their hypothalami contained more prolactin-releasing activity compared with controls. Partial separation of prolactin releasing activity from growth hormone releasing activity in chicken hypothalamic extract was achieved using gel filtration chromatography. Co-incubation studies in vitro with hypothalamic tissue present showed that prolactin release from the pituitary was inhibited and growth hormone release was stimulated when dopamine was added to the medium. The effects of dopamine were blocked by the antagonist pimozide. The possible existence of hypothalamic releasing and inhibiting factors regulating secretion of prolactin and growth hormone is discussed.     

Tissue culture studies on human pituitary tumours: long term release of anterior pituitary hormones into the culture medium.

A study was undertaken to determine the length of time that human pituitary tumours are capable of releasing anterior pituitary polypeptide hormones in vitro under basal conditions and to study the spectrum of hormone release by functioning and "non-functioning" pituitary neoplasms. Fragments from the pituitary tumours of 10 patients in the following categories: 1 Cushing's disease, 2 with amenorrhoea-galactorrhoea, 3 with acromegaly, and 4 with "non-functioning" pituitary tumours and from 2 normal human anterior pituitary glands were placed in primary culture immediately after surgery. The in vitro release of human growth hormone (hGH), prolactin (Prl), thyrotrophin (TSH), adrenocorticotrophin (ACTH), luteinizing hormone (LH), and follicle stimulating hormone (FSH) was measured by specific radioimmunoassays at the end of each week in culture. Hormone release was surveyed from 6 weeks to 6 months depending upon the survival of the culture. Hormone release patterns were compared with clinical and pathological data. In the initial week of the study, all 6 anterior pituitary polypeptides were detected in the media from the 2 control pituitaries and from 4 of the tumours (1 amenorrhoea-galactorrhoea and 3 acromegaly) in concentrations up to 100 ng/ml of medium while 5 of the 6 hormones were readily detectable in the media from 2 additional tumour samples (Cushing's disease and 1 "non-functioning" pituitary tumour). The media of the remaining 4 tumours contained at least 3 of the 6 hormones (1 amenorrhoea-galactorrhoea and 3 "non-functioning" pituitary tumours). After 6 months in culture, the 6 hormones were readily detectable in at least 1 of the 5 surviving cultures and hGH (up to 800 ng/ml) and LH were each detectable in the media from 2 cultures. Although most of the hormone concentrations in the media decreased with length of time in culture, there were 2 exceptions. First in the media from 5 of the 12 cultures from both controls and tumours, Prl concentrations increased after 50 to 80 days culture. This increase usually lasted for several weeks before Prl levels again began to decline. The second unusual finding occurred in a tumour from a patient with acromegaly in the media of which hGH levels rose from 60 ng/ml to 800 ng/ml between days 125 and 174. These findings of prolonged hormone release in vitro give promise of future usefulness of tissue culture methods for study of polypeptide hormone releasing mechanisms and long-term production of human anterior pituitary hormones for use in research and possible therapy.     

On the presence of a nondopaminergic, peptidergic prolactin release-inhibiting factor in hypothalamic extracts of infantile rats

Crude hypothalamic extracts prepared from brains of 1-day-old rats produced a dose-dependent inhibition of prolactin (Prl) release by adult male hemipituitaries, and to a lesser extent by hemipituitaries of adult ovariectomized (OVX), estrogen-primed rats. These extracts contained 6-fold lower levels of dopamine than adult hypothalami. The inhibitory effect of the adult hypothalamic extracts, contrary to infantile hypothalamic extracts could be blocked by spiroperidol. Digestion of the infantile hypothalamic extracts with pronase totally abolished their Prl release-inhibiting activity, indicating the peptidic nature of this inhibitory substance. In contrast to their effect on Prl release by hemipituitaries, infantile hypothalamic extracts stimulated Prl release from dispersed anterior pituitary cells of OVX estrogen-primed rats, pointing to the importance of estrogen in modulating prolactin release-inhibiting factor (PIF) activity and the possibility that the PIF receptor is trypsin-sensitive.     

Altered responsiveness to hypophysiotrophic hormones of perifused rat pituitary tumours.

Since growth hormone (GH) and prolactin (Prl) secretion by human pituitary tumours is often influenced by the hypophysiotrophic hormones thyrotrophin-releasing hormone (TRH) and somatostatin (SRIF), we have examined the responses of several transplantable rat pituitary tumours to these substances in a perifusion apparatus. The MStT/W15 tumour did not alter its secretion of GH and Prl in response to TRH, SRIF, or a partially purified porcine hypothalamic extract containing GH-releasing activity; normal rat pituitaries show clear responses to each of these substances. Theophylline and dibutyryl cyclic AMP each provoked increased GH and Prl release from the tumour. A second specimen of the MStT/W15 tumour and a specimen of the MStT/W5 tumour behaved in a manner identical to the original MStT/W15, showing no response to TRH or SRIF, but releasing both GH and Prl when theophylline or dibutyryl cyclic AMP was given. The MtT/F4 tumour increased its secretion of GH in response to TRH, 10 mug/ml, and theophylline, but no effect was seen with lower concentrations of TRH or with SRIF; Prl secretion by the F4 tumour was increased by theophylline, but TRH and SRIF had no effect. The autonomy demonstrated in these experimental tumours may be due to a loss of specific hypophysiotrophic hormone receptors or of secretory activating mechanisms.     

Somatostatin-28(1-14) immunoneutralization stimulates growth hormone secretion in fowl

Immunoneutralization of endogenous somatostatin (SRIF)-28(1-14) by the intravenous or intramuscular administration of a specific antiserum promptly enhanced the growth hormone (GH) concentration in the plasma of 4 to 8-week-old cockerels. The magnitude of the GH response was related to the volume of antiserum administered. The release of GH from chicken pituitary glands incubated with intact hypothalami was increased in the presence of anti-SRIF-28(1-14). These results suggest that SRIF-28(1-14)-like peptides are physiologically involved in the control of GH secretion in chickens, in which they may tonically inhibit GH release.     

Absence of an effect of naloxone, an opioid antagonist, on luteinizing hormone release in vivo and luteinizing hormone-releasing hormone I release in vitro in intact, castrated, and food restricted cockerels

The possibility that the tonic secretion of luteinizing hormone (LH) and chicken luteinizing hormone-releasing hormone I (LHRH-I) is regulated by an inhibitory action of endogenous opioid peptides was investigated in cockerels using the opiate receptor antagonist, naloxone. Baseline concentrations of plasma LH in the experimental cockerels were increased by surgical castration or reduced by limiting food intake. Baseline and K(+)-induced releases of LHRH-I from perifused mediobasal-preoptic hypothalami from castrated cockerels were higher than those from hypothalami from intact cockerels. Similarly, baseline and K(+)-induced releases of LHRH-I from perifused mediobasal hypothalami from fully fed cockerels were higher than those from the hypothalami from fasting cockerels. Intravenous injections of 0.1, 1, or 10 mg naloxone/kg body weight failed to increase the concentration of plasma LH in castrated, intact, fully fed, or fasted cockerels. Perifusion of mediobasal-preoptic hypothalami from castrated or intact cockerels with 200 microM naloxone or mediobasal hypothalami from fully fed or fasted cockerels with 10 microM naloxone failed to stimulate the release of LHRH-I. These observations suggest in the cockerel that endogenous opioid peptides may not play an obligatory role in the inhibitory control of the tonic secretion of luteinizing hormone.     

The effect of neurotensin on pituitary secretion of thyrotrophin and prolactin in vitro

The effects of neurotensin on thyrotrophin (TSH) and prolactin (Prl) release were studied in two in vitro systems - anterior pituitary cells in culture and perifused anterior pituitary fragments. Neurotensin significantly reduced basal secretion of both TSH and Prl (P less than 0.001) from cultured pituitary cells, and abolished thyrotrophin releasing hormone (TRH)-stimulated TSH thyrotrophin releasing hormone (TRH)-stimulated TSH TSH and Prl release (P less than 0.02) from perifused pituitary fragments. These data indicate that neurotensin has a direct inhibitory effect on TSH and Prl secretion by the anterior pituitary.     

Hypothalamic control of prolactin and growth hormone secretion in different vertebrate species.

Pituitaries from different vertebrates representing mammals, birds, reptiles, and amphibians, were incubated in vitro with various hypothalamic extracts (HE). Prolactin and growth hormone (GH) in medium and pituitary were measured by densitometry after polyacrylamide gel electrophoretic separation (PAGE). Rat (Rattus norvegicus), chicken (Gallus domesticus), terrapin (Chrysemys picta), and toad (Xenopus laevis) pituitaries were incubated with homologous HE. Rat HE inhibited prolactin release. In the other species the HE stimulated prolactin release. In all four species GH release was stimulated by HE. The effects on prolactin and GH release were proportional to the dose of HE added. Chicken pituitaries were incubated with chicken HE together with rat HE. The rat HE inhibited the chicken HE-stimulated release of prolactin, as measured by radioimmunoassay. Heterologous incubations were used to test HE for prolactin releasing and inhibiting factors and for GH releasing and inhibiting factors. Chicken pituitaries were incubated with HE from the eel (Anguilla anguilla), the cod (Gadus gadus) and the flounder (Pleuronectes flesus) as well as from the other species listed. Both cod and flounder HE marginally inhibited autonomous chicken prolactin release. HE from these species dose-responsively inhibited chicken HE-stimulated prolactin release. Cod HE also inhibited chicken HE-stimulated GH release. HE from the eel, the terrapin and the toad stimulated chicken prolactin release. Hormone release from terrapin and toad pituitaries incubated with heterologous HE was consistent with hypothalamic control via releasing factors in these species.     

Growth hormone and prolactin secretion in water-deprived chickens

The deprivation of water for 12 or 24 hr increased the prolactin concentration in the plasma of immature chickens but had no effect on the circulating growth hormone (GH) level. The increase in plasma prolactin level reflected an increase in the basal rate of prolactin release from incubated hemipituitary glands and an increase in the responsiveness of the pituitary gland to hypothalamic releasing factors. The deprivation of water had no effect on basal level of pituitary GH release in vitro but abolished the stimulatory effect of the hypothalamus on in vitro GH secretion.     

Stimulatory and inhibitory effects of prostaglandin E2 on prolactin release in the domestic fowl

In vivo prolactin secretion was increased in immature cockerels 20–30 min after the intravenous administration of prostaglandin (PG) E₂ at a dose of 200 μg/kg. The addition of PGE₂ to incubation medium had no direct effect on the release of pituitary prolactin during short-term (3-hr) culture, but augmented the stimulatory effect of hypothalamic tissue on prolactin secretion. The stimulatory effect of serotonin, noradrenaline, acetylcholine, and histamine on hypothalamus-induced prolactin release was also increased when pituitaries were coincubated with 10^?7M PGE₂, as was the stimulatory effect of thyrotrophin-releasing hormone (TRH) and hypothalamic extract (HE). The long-term (24-hr) preincubation of pituitaries with 10^?7M PGE₂ reduced the responsiveness of the prolactin-secreting cells to TRH or HE stimulation. PGE₂ treatment also reduced the stimulatory effect of hypothalamic tissue on prolactin release and diminished the stimulatory effect of serotonin on hypothalamus-induced prolactin secretion. A 24-hr preincubation of hypothalamic tissue with 10^?7M PGE₂ also reduced its stimulatory effect on prolactin release when subsequently incubated with control pituitary glands. These results demonstrate that PGE₂ initially stimulates in vivo and in vitro prolactin secretion in the fowl, possibly by increasing the release of hypothalamic prolactin-releasing activity and/or by increasing pituitary sensitivity to provocative stimuli. Chronic PGE₂ stimulation appears to result in a reduction in pituitary responsiveness to stimulatory influences and in the release of hypothalamic-releasing activity.     

Control of prolactin and growth hormone secretion in the eel Anguilla anguilla

Freshwater eels were placed in seawater, and changes in pituitary prolactin and growth hormone were determined. The content of both hormones declined initially but returned to the original values after 8 weeks. Whole glands were not seen to differ in their prolactin release in vitro from pituitary fragments consisting of the rostral pars distalis only. Release of prolactin and growth hormone in vitro was directly proportional to the amount of hypothalamic extract added. During adaptation to seawater the amount of prolactin- and growth hormone-stimulating ability in the hypothalamus decreased, but the pituitaries of SW-adapted eels were still capable of responding to HE from FW eels.     

Histologic identification and immunochemical studies of prolactin and growth hormone in the primate pituitary gland

The two acidophilic cell types were tinctorially differentiated in rhesus monkey pituitaries as well as in pituitaries of other species of monkeys and apes and were identified by immunofluorescence as the prolactin and the growth hormone (GH) cells. The number of prolactin cells was significantly greater in adult than in juvenile rhesus monkeys. During late pregnancy and lactation, these cells appeared to occupy 60–80% of the entire anterior lobe of the rhesus monkey. The concentration of prolactin and CH was measured by radioimmunoassay in pituitary extracts (PE) from pools of juvenile male, juvenile female, adult male and adult female rhesus monkey pituitaries. More prolactin was present in PEs from adult than from juvenile animals, with the highest concentration being present in adult females. A similar relationship was observed with GH. The qualitative immunologic relationship between ovine prolactin and prolactin in the rhesus monkey PEs, and between human GH and GH in the PEs, was established using agar gel diffusion. The two prolactin hormones were partially related immunochemically, while the two GHs were shown to be immunochemically identical. In intact juvenile female rhesus monkeys given estradiol benzoate, the concentrations of pituitary and serum prolactin were elevated over that of the controls, while the concentration of pituitary GH was decreased. An increase in the number of prolactin cells was also observed in the steroid-treated animals. These observations demonstrate further that prolactin and GH reside in separate cells in the primate pituitary and that the concentration of these two hormones varies depending upon age, sex, or stage of the reproductive cycle of the animal.     

The effect of thyrotropin-releasing hormone (TRH) and somatostatin (GHRIH) on growth hormone and prolactin secretion in vitro and in vivo in the domestic fowl (Gallus domesticus).

The effects of thyrotropin-releasing hormone (TRH) on growth hormone (GH) and prolactin (Prl) secretion have been investigated in vitro and in vivo in domestic fowl. In both conscious and anaesthetized immature chickens the administration (i.v.) of TRH (2.5 and 25 microgram/kg) significantly increased the concentration of plasma GH. The simultaneous administration of somatostatin (GHRIH), 2.5 microgram/kg, to conscious birds significantly reduced the magnitude of the GH response to TRH treatment, but had no effect on the basal levels of plasma GH. The repeated injection of TRH (10 microgram/kg) every 20 min over a 100-min period failed to maintain the concentration of plasma GH at a high level. Prl secretion was not stimulated in any of these experiments, and in anaesthetized birds TRH (2.5 and 25 microgram/kg) treatment was followed by a depression in the level of plasma Prl. The effects of TRH and GHRIH on GH secretion by an in vitro dispersed pituitary cell suspension system were very similar to the in vivo studies. TRH stimulated Prl release in vitro, in contrast to the in vivo studies, and the response was dose related. GHRIH had no effect on the basal release of Prl in vitro but significantly inhibited the response to TRH treatment.     

Evidence of a circulating growth hormone stimulating factor other than growth hormone releasing hormone in a patient with pituitary tumour and acromegaly

This study is a report on the growth hormone (GH) stimulatory effect of serum and plasma from a patient with notably active acromegaly due to a GH producing pituitary adenoma. Pituitary adenomatous tissue from 7 patients with GH producing adenomas, one with a prolactin (Prl) producing adenoma, one with a TSH producing adenoma, and one with a non-secreting adenoma, were cultured in vitro for 8-10 days. Media were changed every 48-72 h and contained Neumann Tytell buffer with the addition of 1) foetal calf serum, 2) patients' own serum or plasma, 3) serum or plasma from the patient with notably active acromegaly. GH release expressed as microgram GH/1/48-72 h between day 6 and 8 in culture did not differ when adenomatous tissue was cultured in buffer, foetal calf serum or the patients' own serum or plasma. In contrast, GH release was increased in 9/10 patients, when media contained serum or plasma from the patient with notably active acromegaly. This GH stimulatory effect was demonstrated in vitro in human pituitary adenomatous tissue from patients with pathological as well as normal GH secretion in vivo. Furthermore, this GH releasing plasma in a concentration of 10% increased GH release in cultures of dispersed rat anterior pituitary cells. In the same system, synthetic growth hormone-releasing hormone (GRF)-44 stimulated the release of GH in a dose-dependent manner. However, at all dose levels including maximally stimulating doses of GRF, an additive effect on GH release was seen with 10% of the GH releasing plasma.(ABSTRACT TRUNCATED AT 250 WORDS)