Chicken Pituitary Research Articles

Chicken growth hormone: further characterization and ontogenic changes of an N-glycosylated isoform in the anterior pituitary gland

Glycosylation is one of the post-translational modifications that growth hormone (GH) can undergo. This has been reported for human, rat, mouse, pig, chicken and buffalo GH. The nature and significance of GH glycosylation remains to be elucidated. This present study further characterizes glycosylated chicken GH (G-cGH) and examines changes in the pituitary concentration of G-cGH during embryonic development and post hatching growth. G-cGH was purified from chicken pituitaries by affinity chromatography (Concanavalin A–Sepharose and monoclonal antibody bound to Sepharose). Immunoreactive G-cGH has a MW of 26 kDa or 29 kDa as determined by SDS–PAGE, respectively, under non-reducing and reducing conditions. Evidence that it is N-glycosylated comes from its susceptibility to peptide N-glycosidase F, and its resistance to O-glycosidase. Based on the ability of G-cGH to bind Concanavalin A or wheat germ agglutinin but not other lectins and its susceptibility to peptide N-glycosidase F, a hybrid or biantennary type glycopeptide (GlcNac2, Man) structure is proposed. Some G-cGH can be observed in the pituitary at most ages examined (from 15-day embryo to adult). Moreover, electron microscopy revealed the presence of both immuno-reactive GH and Concanavalin A-reactive sites in the same secretory granules in the somatotrope. There were marked changes in the level and relative proportion of G-cGH in the pituitary gland during development and growth, the proportion of G-cGH rising during late embryonic development (e.g., between 15 and 18 days of development) and with further increases between 9 weeks and 15 weeks old. G-cGH was able to bind to chicken liver membrane preparations with less affinity than non-glycosylated monomer; on the other hand, however, G-cGH stimulated cell proliferation on Nb2 lymphoma bioassay whereas the non-glycosylated monomer was uncapable to do it.

The chicken pituitary expresses an ovoinhibitor-like protein in subpopulations of some, but not all, hormone-producing cell types

Ovoinhibitor is a serine protease-inhibiting protein that was originally purified from egg whites. It is secreted by the oviduct under the control of estrogen and progesterone and it specifically inhibits serine proteinases such as trypsin and chymotrypsin. During recent attempts to raise monoclonal antibodies (Mabs) against chicken bursa of Fabricius proteins, one Mab was produced that specifically recognized chicken ovoinhibitor. This was the first demonstration of ovoinhibitor in an avian immune organ. We presently report on the expression of an ovoinhibitor-like molecule by the pituitary of the chicken as revealed by immunocytochemistry and RT-PCR. Immunofluorescent dual staining experiments using the mouse anti-ovoinhibitor Mab in conjunction with polyclonal antibodies against various hypophysial hormones revealed partial co-localization of an ovoinhibitor-like molecule with growth hormone (GH), luteinizing hormone (LH), and pro-opiomelanocortin (POMC), in a subset of the respective hormone producing cells. By contrast, no co-localization with prolactin (PRL) could be reliably demonstrated. RT-PCR of hypophysial mRNA using ovoinhibitor gene-specific primers yielded an amplicon that was 20% shorter than predicted on the basis of the published ovoinhibitor sequence. Sequencing revealed that of the represented exons only the central portion was expressed in the pituitary and that both 5′ and 3′ ends of each exon had been truncated. While expression of ovalbumin-like serine protease inhibitors (serpins) has been previously reported in the rat pituitary, to our knowledge, this is the first report of a Kazal-type serine protease inhibitor in the vertebrate neuroendocrine system.

Changes in the population of pituitary protein transcription factor-1 nuclei in the anterior pituitary during withdrawal and resumption of feeding in hens

Pituitary protein transcription factor (Pit-1) is a member of a large family of protein transcription factors that include Pit-1, Oct-1, Oct-2, and Unc-86. The goal of this experiment was to determine whether the population of Pit-1-containing cells changes in the anterior pituitary of chicken by the regulation of feeding. White Leghorn hens were subjected to withdrawal and resumption of feeding. The anterior pituitaries were collected from hens at pretreatment, at 2 d after withdrawal of feeding (2DWF), and 1 d and 5 d after resumption of feeding (1DRF and 5DRF, respectively). Sections of the pituitaries were immunostained for Pit-1. They were examined under a light microscope with an image analysis computer system. The Pit-1 positive nuclei were found in the glandular cells in the cephalic and caudal lobes of the anterior pituitary in all four groups of hens. The Pit-1 cell population significantly increased in the 2DWF and 1DRF and decreased thereafter in 5DRF. These results suggests that feed withdrawal may stimulate Pit-1 expression in chicken, suggesting that Pit-1 may be involved in control of pituitary functions during the process of feed regulation.

Immunohistochemical localization of chromogranin A in gonadotrophs and somatotrophs of the turkey and chicken pituitary

In the course of producing monoclonal antibodies to turkey prolactin, three monoclonal antibodies to turkey chromogranin A (CgA) were also produced, apparently arising from minor contamination of the turkey prolactin immunogen with peptide fragments of CgA. The identity of the antigen recognized by these antibodies was established by tandem mass spectrometry de novo sequencing of seven tryptic peptides from a turkey pituitary protein purified by immunoaffinity chromatography. These peptides showed high homology with distinctly separate regions of mammalian and ostrich CgA, and in silico cloned chicken CgA sequences. Chromogranin A immunostaining patterns on Western blots and pituitary tissue sections differed from those of prolactin, growth hormone, or luteinizing hormone (LH). Dual-label fluorescent immunohistochemistry revealed that CgA was co-localized with LH in most avian gonadotrophs in young chickens and turkeys, but not in adult, laying birds. Conversely, CgA was found in a majority of somatotrophs in laying birds but was absent from somatotrophs in young, growing chickens and turkeys. Lactotrophs contained no detectable CgA immunoreactivity in the tissues studied. These results suggest that CgA may modulate hormone secretion by gonadotrophs and somatotrophs in a manner that differs between cell type with age or reproductive state.

Identification of somatostatin receptors controlling growth hormone and thyrotropin secretion in the chicken using receptor subtype-specific agonists.

Somatostatin (SRIH) functions as an endocrine mediator in processes such as growth, immune resistance and reproduction. Five SRIH receptors (sstr1-5) have been identified in mammals, where they are expressed in both the brain and peripheral tIssues. To study the specific function of each receptor subtype, specific agonists (ag1-5) have been synthesized. The high degree of homology between mammalian and avian SRIH receptors suggests that these agonists might also be used in chickens. In this paper we describe two in vitro protocols (static incubation and perifusion system) to identify the SRIH receptors controlling the secretion of GH and TSH from the chicken pituitary. We found that basal GH or TSH secretion were never affected when SRIH or an agonist (1 microM) were added. SRIH diminished the GH as well as the TSH response to TSH-releasing hormone (TRH; 100 nM) in both systems. Our results have indicated that the SRIH actions at the level of the pituitary are regulated through specific receptor subtypes. In both the static and flow incubations, ag2 lowered the GH response to TRH, whereas stimulated TSH release was diminished by both ag2 and ag5. Ag3 and ag4 tended to increase rather than decrease the responsiveness of both pituitary cell types to TRH in perifusion studies. Our data have indicated that SRIH inhibits chicken pituitary function through sstr2 and sstr5. Only sstr2 seems to be involved in the control of chicken GH release, whereas both sstr2 and sstr5 inhibit induced GH secretion in mammals. The possible stimulatory action of ag3 and ag4 may point towards a species-specific function of sstr3 and sstr4.

Immunocytochemical identification of Pit-1 containing cells in the anterior pituitary of hens.

Our goal was to identify the cells expressing Pit-1 protein in chicken anterior pituitary. The anterior pituitaries were collected from laying hens after perfusion with formalin-PBS, and fixed with Bouin's fixative followed by paraffin embedding. Sections of the anterior pituitaries were immunostained for Pit-1 in the first staining sequence followed by staining for 6 types of pituitary hormones in the second sequence. Pit-1 positive nuclei were observed in the glandular cells in both the cephalic and caudal lobes. Pit-1 immunoreaction products were colocalized in the glandular cells immunopositive for growth hormone, thyroid-stimulating hormone, follicle-stimulating hormone, luteinizing hormone, adrenocorticotropic hormone or prolactin. These results indicate that Pit-1 protein induction occurs in 6 types of glandular cells, suggesting that Pit-1 may regulate hormone synthesis in each glandular cell in the chicken pituitary.

Cell Proliferation and Apoptosis in the Anterior Pituitary of Chicken during Inhibition and Resumption of Laying

The goal of this study was to determine whether tissue rejuvenation of the anterior pituitary with cell proliferation and apoptosis occurs during inhibition and resumption of egg-laying. White Leghorn laying hens were subjected to inhibition of laying by feed withdrawal. Feeding was resumed on the fourth day of egg-laying cessation. All birds were injected ip with bromodeoxyuridine (BrdU) 1 h before tissue collection. The anterior pituitary glands were collected from hens of the following groups: pretreatment (PT), 3 and 5 days after starvation (3DS and 5DS, respectively), 3 days after cessation of laying (3DC), 10 days after cessation of laying (10DC, 6 days after resumption of feeding), and the day of and 1 week after resumption of laying (RL and 1WRL, respectively). They were processed for the detection of proliferating cells and apoptotic cells by BrdU immunostaining and terminal deoxynucleotidyl transferase-mediated biotinylated deoxyuridine triphosphate nick-end-labeling (TUNEL). Immunostaining for the anterior pituitary hormones was also conducted. In the cephalic lobe the BrdU-positive cells showed a higher frequency in RL than in PT, 3DC, and 1WRL. BrdU-positive cell frequency in the caudal lobe was greater in RL than in PT. TUNEL-positive cells in both cephalic and caudal lobes were increased markedly in the RL group. Their frequency in the cephalic lobe was greater in RL than in PT, and that in the caudal lobe of RL was higher than in any other group of birds. The areas of FSH-like cells in 10DC and RL were greater than those in PT to 3DC, and those of LH-like cells in RL were greater than those of 3DS to 3DC. PRL-like cells were decreased until 3DC and then gradually increased until 1WRL. GH-, TSH-, and ACTH-like cell areas showed tendencies to increase until 3DC, with decreasing thereafter. The sizes of FSH-like cells in 10DC to 1WRL and LH-like cells in RL were larger than those around cessation of laying. These results suggest that during inhibition and resumption of laying cell proliferation and apoptosis occur in the anterior pituitary tissue, which may cause a rejuvenation of tissue to improve the function of this organ.

Complementary DNA Cloning and Ontogenic Expression of Pituitary-Specific Transcription Factor of Chickens (Gallus domesticus) from the Pituitary Gland

Pit-1 is a pituitary-specific POU-domain DNA binding factor, which binds to and transactivates promoters of growth hormone (GH)-, prolactin (PRL)-, and thyroid-stimulating hormone-beta (TSHβ)-encoding genes. Pit-1 has been identified in several mammalian species. In birds, it has been identified only in the turkey and chicken pituitary. Several (gg) Pit-1 cDNA sequences have been identified in the anterior pituitary of the chicken (Gallus domesticus). As in turkey, three different transcripts (ggPit-1*, ggPit-1β*, and ggPit-1W*) of the Pit-1 gene were identified. This suggests that the chicken pituitary expresses more variants than reported earlier. Previous studies have concentrated on expressions during posthatch life of the turkey and chicken. The present study has determined the ontogeny of Pit-1 during the embryonic life of the chicken (day 1–day 21 of incubation). The mRNA for Pit-1 was first detected in the pituitary on day 5 of embryonic life. The expression of the mRNA was maintained until hatch. The presence of Pit-1 at this stage of embryonic development suggests that Pit-1 may be physiologically important during embryonic development of birds, as it precedes the gene expression and secretion of GH, PRL, and TSHβ. A similar sequence for the expression of Pit-1 relative to GH and PRL during embryonic/fetal development has been reported for rodents.

Adrenal inhibition of corticotropin-releasing hormone-induced thyrotropin release: A comparative study in pre- and posthatch chicks

Recent evidence indicates that corticotropin-releasing hormone (CRH) acts as a potent stimulator of thyrotropin (TSH) release in the chicken. In this study adrenal and thyroidal feedback mechanisms were studied. Administration of corticosterone 30 min prior to an ovine CRH (oCRH) challenge diminished the in vivo sensitivity of thyrotrophs to oCRH in 19-day-old chicken embryos (E19) (20 micrograms corticosterone; 2 micrograms oCRH) but not in 8-day-old chickens (C8) (40 micrograms corticosterone; 4 micrograms oCRH). At both ages studied, corticosterone (0.01 and 1 microM) did not alter the in vitro TSH response to oCRH (100 nM) indicating that an indirect mechanism is involved at the embryonic stage which is no longer present in posthatch chickens. In vitro, 3,5,3'-triiodothyronine (T3) pretreatment (0.01 and 1 microM) resulted at both ages studied in a dose-dependent drop in the in vitro oCRH-induced TSH release. As recorded previously, corticosterone treatment provoked a rise in plasma T3 in embryonic but not in posthatch chickens. The presence of an indirect adrenal feedback mechanism in chicken embryos may therefore be linked to the increase in plasma T3 which will alter the sensitivity of thyrotrophs to hypothalamic releasing factors. In conclusion, corticosterone does not directly modulate the responsiveness of thyrotrophs to CRH, but its feedback mechanism may be dependent on the evoked increase in plasma T3 which is only present in embryonic chickens. Corticosterone may in this regard play an essential role during embryonic development by coordinating thyroidal feedback mechanisms at the level of the chicken pituitary.

CDNA Cloning and Developmental Alterations in Gene Expression of the Two Pit-1/GHF-1 Transcription Factors in the Chicken Pituitary

Pit-1/GHF-1 (Pit-1) transcription factors promote the gene expressions for growth hormone (GH), prolactin (PRL), and the β chain of thyroid-stimulating hormone in vertebrate pituitary glands. The present study analyzed the nature of chicken Pit-1s (cPit-1s) and their developmental expressions in the pituitary. Chicken pituitary expressed two cPit-1 mRNAs encoding cPit-1α and cPit-1γ composed of 335 and 327 amino acid residues, respectively. They possessed different N-terminal regions and the common C-terminal regions containing a POU-specific domain and a POU homeodomain. Northern blot analysis revealed the pituitary-specific expressions of these Pit-1 mRNAs, and the Pit-1α mRNA expressions were two to three times higher than those for Pit-1γ in both cephalic and caudal lobes of the pituitary. The cPit-1α and γ mRNA expressions simultaneously increased after hatching until 4 weeks and then slightly decreased at 5 weeks. Similar gene expression profiles were observed for GH and PRL during the posthatch developmental period.

Immunohistochemical evidence that follicle-stimulating hormone and luteinizing hormone reside in separate cells in the chicken pituitary.

As is the case in other tetrapod species, the chicken gonadotropins LH and FSH consist of a common alpha subunit and a hormone-specific beta subunit. Gonadotrophs containing LH were shown earlier to be distributed throughout both the caudal and cephalic lobes of the chicken anterior pituitary, but the cellular distribution of FSH in avian species is still uncertain. The purpose of this study was to determine the cellular distribution of FSH-containing chicken gonadotrophs by use of FSH-specific monoclonal antibodies (mAbs). Three new mAbs toward chicken FSH were proven hormone specific by immunodetection of purified hormones on dot blots and by dual-label immunohistochemistry (IHC) on sagittal sections of chicken pituitaries. A rabbit antibody was used to detect chicken LH. Results showed that LH-containing gonadotrophs were densely distributed throughout the anterior pituitary, whereas gonadotrophs containing FSH were much less numerous; in addition, while also present in both lobes, FSH-positive cells were largely absent from the outer margin of the gland. Dual-label IHC revealed that LH and FSH reside almost exclusively in separate gonadotrophs. The identity of FSH-containing cells was further confirmed through use of an antibody to the chicken alpha subunit, which showed that FSH immunoreactivity was always colocalized with the alpha subunit. Our results suggest the possibility that production and secretion of LH and FSH may be regulated differently in chickens than in most other species studied to date.

Thyrotropin-releasing hormone concentrations in different regions of the chicken brain and pituitary: an ontogenetic study

The regional distribution of thyrotropin-releasing hormone (TRH) was studied in the chicken brain. The hypothalamus and the brain stem contained the highest concentration of TRH. Lower amounts were present in the telencephalon, the optic lobes and the cerebellum. Within the hypothalamus, TRH was most abundant in the median eminence. Other important TRH sites were the nucleus paraventricularis magnocellularis, nucleus periventricularis hypothalami, nucleus ventromedialis hypothalami, nucleus dorsomedialis hypothalami and nucleus preopticus periventricularis. On the 14th day of embryonic development (E14), TRH was mostly found in the brain stem. Towards hatching, TRH concentrations increased gradually in both the hypothalamic area and the brain stem. TRH concentrations in the telencephalon, optic lobes and cerebellum remained low. Pituitaries from E14 to E16 chickens were characterized by a high TRH concentration, whereas hypophyseal TRH concentrations dropped towards hatching. Our results support the hypothesis that TRH exerts both endocrine and neurocrine actions in the chicken. On the other hand, high pituitary TRH concentrations were present when hypothalamic concentrations were low and vice versa. Therefore, the chicken pituitary may function as an important source of TRH during early in ovo development at least until the moment hypothalamic control develops.

Chicken Pituitary Glycoproteins: New Isolation Method

A new method for isolation of glycoproteins from chicken pituitaries was applied. The procedure consist of chromatography on ConA-Sepharose and by HPLC on S Hyper D and Vydac C4 columns. The hormonal activity of the glycoproteins was tested by determining their stimulatory effect on cAMP or testosterone production. Molecular weights of the products of tryptic cleavage of the hormone were determined using mass spectrometry (MALDI TOF). A comparison of the values obtained with theory shows that the protein is the β-unit of chicken luteinizing hormone.

Evaluation of a sensitive, in vitro bioassay for chicken thyroid stimulating hormone using FRTL-5 cells, a rat thyroid cell line

An in vitro bioassay for mammalian thyroid stimulating hormone (TSH) based on TSH-induced cyclic adenosine 3',5'-monophosphate (cAMP) production in FRTL-5 cells, a rat thyroid cell line, was used to measure chicken TSH. The addition of chicken pituitary homogenate equivalent to > or = 25% of a chicken pituitary gland to cultured FRTL-5 cells increased cAMP within these cells in a dose-dependent manner. The glycoprotein fraction derived from the pituitary homogenate was further fractionated by isoelectric focusing within a pH range of 5 to 11. Analysis of the focused fractions by the bioassay detected three major components with isoelectric points of 9.30, 7.12, and 3.82, in addition to several minor ones distributed over a wide range of pH, from alkaline to acidic. The isoelectric focusing profile obtained by the bioassay was clearly different from those obtained by radioimmunoassay for chicken LH and radioreceptor assay for chicken FSH, indicating that fractions contained chicken TSH. The homogenate of the cephalic portion of the chicken anterior pituitary gland was 4.46 times more active than that of the caudal portion in the bioassay, which is consistent with previous findings on localization of TSH in the chicken pituitary. We conclude that the bioassay using FRTL-5 rat thyroid cells is a sensitive, specific, and time-saving method of measuring chicken TSH.

Uneven Regional Distributions of Prolactin- and Growth Hormone-Secreting Cells and Sexually Dimorphic Proportions of Prolactin Secretors in the Adenohypophysis of Adult Chickens

Prolactin (PRL) and growth hormone (GH) proteins are structurally similar and are thought to be evolutionarily derived from a common gene. In addition, data indicate that GH and PRL cells differentiate from a common stem cell. In adult birds, females have higher levels of serum PRL than males. Levels of serum GH are reported to be higher in young male birds than in females and equal between sexes in adult birds. Furthermore, previous studies using immunocytochemistry found that PRL- and GH-containing cells were located primarily in the cephalic (Cp) and caudal (Cd) lobes. respectively, of the anterior pituitary. Two experiments were conducted to study the cellular basis for differences in PRL and GH secretion between genders or anatomical location in adult chickens. In Experiment I, anterior pituitaries from broiler breeder adult hens and roosters were subjected to reverse hemolytic plaque assays (RHPA's) for PRL and GH. The percentage of PRL-secreting cells was significantly greater in females than in males (46.1 ± 4.5% and 26.1 ± 2.4%, respectively: P < 0.001; n = 6). However, there were no significant differences between the proportions of GH-secreting cells between sexes (25.8 ± 3.1% and 30.0 ± 3.9% in females and males, respectively). Average area of plaques formed was different between sexes in GH plaque assays under basal conditions (162,465.9 ± 29,911.8 μm2 and 53,834.9 ± 31,033.5 μm2, for males and females, respectively P < 0.05). However, no differences were found in the presence of GH-releasing hormone. In Experiment II, anterior pituitaries from Leghorn hens were dissected into three regions: the extreme portions of the Cp and Cd lobes and the remaining or middle portion. The cells from each region were subjected to RHPA's for PRL and GH. We found that 52.0 ± 4.1% of all cells from the Cp lobe secreted PRL. This proportion was greater (P < 0.01; n = 4) than that found in the Cd lobe, where 2.4 ± 0.4% of all cells released PRL. In contrast, the percentage of GH-secreting cells was higher in the Cd lobe than in the Cp lobe (61.0 ± 2.3% and 0.8 ± 0.5%, respectively: P < 0.01). As expected, the middle portion contained substantial numbers of both cell types. These findings suggest that sexual dimorphism in serum PRL levels in adult chickens is due, in part, to an increased cell population of PRL secretions in females. Furthermore, PRL- and GH-secreting cells are distributed unevenly throughout the anterior pituitary of chickens, with the PRL secretors localized to the Cp lobe and the GH secretors to the Cd lobe.

Purification and partial characterization of isoforms of luteinizing hormone from the chicken pituitary gland

Isoforms of chicken luteinizing hormone (cLH) were isolated from chicken pituitaries by differential extraction, sequential chromatography on HPLC cation- and anion-exchange columns, and gel-filtration chromatography. Three purified isoforms of the cLH had high biological potency in the chicken granulosa cell LH bioassay (4.21–7.4 × NIH-LH-S1 U/mg). One cLH isoform without detectable biological activity showed substantial immunological activity in a homologous cLH radioimmunoassay. The cLH isoforms contained negligible follicle-stimulating hormone activity, but some contained thyroid-stimulating hormone activity. The apparent molecular weight of cLH was 37,000 Da, and the holoprotein consisted of subunits with a molecular weight of approximately 17,000 Da.

Properties of Vasoactive Intestinal Polypeptide Receptors in the Anterior Pituitary of Female Chickens.

The membrane fraction of anterior pituitary in laying hens was found to possess a vasoactive intestinal polypeptide (VIP)-binding component having the properties of a receptor. Scatchard analysis of saturation studies revealed that the binding component had a single class of binding site with an equilibrium dissociation constant (Kd) of 0.092 ± 0.008 (mean ± SEM; n=5) nM and the maximum binding capacity (Bmax) of 631 ± 41 fmol/mg protein. The Kd value determined from kinetic analysis (0.091 ± 0.002 nM; n=3) was very similar to that obtained from Scatchard analysis. The Kd value obtained from Scatchard analysis was not significantly different between the laying and nonlaying hens. The Bmax in laying hens was greater than that in nonlaying hens. The administration of chicken VIP to nonlaying hens caused a marked decrease in the VIP receptor binding in the anterior pituitary with a concomitant increase in the blood serum concentrations of prolactin. The results may provide an evidence for a direct action of VIP on the anterior pituitary of female chickens.

Presence of Vasotocin Receptors in the Anterior Pituitary of Chicken.

Presence of Vasotocin Receptors in the Anterior Pituitary of Chicken.

Expression of the growth hormone receptor gene in chicken pituitary glands.

Although GH has no direct effect on GH release from chicken pituitary glands, GH receptor mRNA similar to that in the rabbit liver was identified by Northern blot analysis in extracts of adult chicken pituitaries. Complementary (c) DNA, reverse transcribed from chicken pituitary RNA, was amplified by the polymerase chain reaction (PCR) in the presence of 3'- and 5'-oligonucleotide primers coding for the extracellular domain of the chicken liver GH receptor and was found to contain an electrophoretically separable fragment of 500 bp, identical in size to that in chicken liver. Digestion of this pituitary cDNA with NcoI produced expected moities of 350 and 150 bp. Amplification of chicken pituitary cDNA in the presence of oligonucleotide primers for the intracellular sequence of the chicken liver GH receptor produced an electrophoretically separable fragment of approximately 800 bp, similar to that in chicken liver. This fragment was cut into expected moieties of 530 and 275 bp after digestion with EcoRI. These PCR fragments were identified in extracts of the pituitary caudal lobe, in which somatotrophs are confined and account for the majority of endocrine cell types, and in the cephalic lobe, in which somatotrophs are lacking. Translation of the GH receptor mRNA in the pituitary gland was indicated by the qualitative demonstration of radiolabelled GH-binding sites in plasma membrane preparations, in pituitary cytosol and in nuclear membranes. These results provide evidence for the expression and translation of the GH receptor gene in pituitary tissue, in which GH receptors appear to be widely distributed within cells and in different cell types. GH may therefore have paracrine, autocrine or intracrine effects on pituitary function.

Induction of ovarian growth and ovulation by administration of a chicken gonadotrophin preparation to Japanese quail kept under a short-day regimen.

1. Chronic administration of a glycoprotein fraction from chicken pituitary using an ALZET osmotic pump at 12.5 micrograms/h for 2 weeks induced growth of ovarian follicles to a mature size in the ovary and deposition of yolk in sexually immature 6-week-old Japanese quail females which were kept under 8L:16D short-day conditions. However, no ovulation was induced in these birds. 2. Injection of 500 micrograms of the glycoprotein into other immature short-day females was performed following the above chronic administration, 12 or 14 and 15 d after implantation of the osmotic pump. About 24 h after injection, 3 of 14 females laid one or two eggs. Ovulation was confirmed in 4 females by autopsy. A total of 5 of 14 females ovulated 6 eggs, and significant development of the oviduct and the cloacal opening were observed in all of the treated females. 3. Thus, complete ovarian function could be induced in sexually immature female Japanese quail by administration of avian gonadotrophin using a combination of an osmotic pump and an injection.