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PubMed2000

Atrial natriuretic peptide binding sites in the brain and pituitary gland of the toad, Bufo marinus: localisation and receptor characterisation.

The distribution and nature of 125I-atrial natriuretic peptide binding sites have been examined in the brain and pituitary gland of the toad, Bufo marinus, using tissue section autoradiography, affinity cross-linking and electrophoresis, guanylyl cyclase assays and molecular analysis of natriuretic peptide receptor C (NPR-C) and NPR-GC mRNA expression. The highest density of 125I-atrial natriuretic peptide binding sites occurred in the dorsal pallium, the habenular region, the torus semicircularis, the choroid plexus, and the pituitary gland. Less dense binding was observed in the medial pallium, the thalamic region, the hypothalamus, the optic tectum, and the interpeduncular nucleus. The natriuretic peptide receptor-C specific ligand, C-ANF, displaced the binding in all brain regions; however, some residual binding was observed in the habenular region, the hypothalamus, the choroid plexus, and the pituitary gland. In isolated brain membranes, 1 microM rat atrial natriuretic peptide increased cyclic guanosine monophosphate levels to 90% above basal. Affinity cross-linking followed by reducing electrophoresis showed that 125I-atrial natriuretic peptide bound to proteins of 65 kDa and 135 kDa respectively. Furthermore, molecular analysis demonstrated that natriuretic peptide receptor-C and guanylyl cyclase messenger ribonucleic acid are expressed in the brain. In combination with the autoradiography, the data indicated that atrial natriuretic peptide acting via specific receptors could be important in natriuretic peptide regulation of the brain.

Animals↗
PubMed1985

Thyroxine 5'-deiodinase activity in anterior pituitary glands transplanted under the renal capsule in the rat.

The conversion of T4 to T3 by the anterior pituitary gland appears to be of considerable physiological importance in the control of pituitary function. To determine a possible role of hypothalamic factors in controlling this enzymatic process, iodothyronine 5'-deiodinase (I5'D) activity was studied in rats 6 weeks after homologous transplantation of pituitary (implanted animals) or muscle tissue (sham animals) under the renal capsule. Intrasellar pituitaries remained intact, and serum T3, T4, and TSH levels were similar in both groups. I5'D activity was determined by quantifying T3 production rates in tissue homogenates at T4 concentrations of 0.002-4 microM, and with 20 mM dithiothreitol. Sellar pituitaries from sham and implanted animals displayed similar nonlinear reaction kinetics, suggesting the presence of two enzymatic processes having approximate Michaelis-Menten constant (Km) values of 2 nM and 0.3 microM. Maximum velocity (Vmax) was 51.3 +/- (SE) 4.0 fmol T3/min X mg protein (units) and 40 +/- 6 U for the low and high Km components, respectively. In transplanted pituitary tissue, I5'D activity was markedly altered; the low Km activity was significantly decreased (Km, 6 nM; Vmax, 13.0 +/- 1.1 U; P less than 0.001 compared to sellar pituitaries), whereas the high Km activity was increased 15-fold (Km, 5 microM; Vmax, 620 U). The in vitro addition of 6-n-propyl-2-thiouracil (0.1 mM) inhibited high Km I5'D activity in homogenates of both transplanted pituitary and renal tissue by approximately 50% (P less than 0.001), but had no effect on low Km I5'D activity in either sellar or transplanted pituitaries. In sham and implanted animals rendered hypothyroid by the inclusion of 1 g/dl NaClO4 in their drinking water for 6 weeks, low Km I5'D activity was increased approximately 3-fold in sellar and transplanted pituitary tissue. The levels of activity reached in transplanted tissue, however, were only 20-30% of those noted in sellar pituitary homogenates (P less than 0.001). High Km I5'D activity was estimated to be decreased 55% in transplanted tissue from hypothyroid animals. These studies demonstrate that transplantation of the anterior pituitary gland under the renal capsule in the rat results in marked alterations in two distinct components of pituitary I5'D activity. This suggests that neuroendocrine factors are important in the control of pituitary T4 to T3 conversion. Furthermore, it provides evidence for a unique mechanism whereby the hypothalamus, by modulating local thyroid hormone metabolism, may influence pituitary function.

Animals↗
PubMed1985

Corticotropin-releasing factor receptors in human pituitary gland: autoradiographic localization.

Corticotropin-releasing factor (CRF) receptors were localized in the human pituitary gland by an in vitro labeling light microscopic autoradiographic technique using an 125I-labeled analog of ovine CRF substituted with norleucine and tyrosine at amino acid residues 21 and 32, respectively. Specific binding sites for CRF were observed in the anterior lobe while no specific binding sites for CRF were present in the posterior pituitary lobe. The CRF binding sites in the anterior lobe occurred in clusters which predominated in the anteromedial portion of the lobe. This pattern of localization of CRF binding sites resembles previously reported distributions of corticotrophs in anterior pituitary. These data support the physiological role of endogenous CRF in regulating hormone secretion from the anterior lobe of the human pituitary.

Autoradiography↗
PubMed1983

Plasminogen activators of the pituitary gland: enzyme characterization and hormonal modulation.

We studied plasminogen activator (PA) of the rat pituitary gland in organ and cell monolayer culture. Both anterior and intermediate lobes contain, synthesize and secrete a mixture consisting of the two known types of PA: urokinase and so-called tissue PA. Both enzymes were formed essentially by all PA secreting cells, and PA was identified specifically in mammotrophs, corticotrophs, and luteinizing hormone containing gonadotrophs. Pituitary PA production was modulated on exposure to a variety of biological effectors: anterior lobe PA secretion was stimulated by agents that raised intracellular cAMP concentration; his process depended on de novo enzyme synthesis. Enzyme production was repressed by androgens and glucocorticoids. When anterior lobe cultures were maintained in plasminogen-free media, the extracellular, secreted forms of ACTH consisted almost exclusively of the high molecular weight forms (31,000 and 23,000); the smaller forms (13,000 and 4,500) were also found in the extracellular medium of cultures supplemented with plasminogen. In contrast, the size distribution of intracellular ACTH species was unaffected by the presence of plasminogen. These results resemble those previously obtained with pancreatic islets and are consistent with the possibility that plasmin, generated by PA secretion, participates in prohormone processing. PA synthesis in intermediate lobe explants was stimulated by exposure to dibutyryl cAMP, and repressed by hydrocortisone. In accordance with the dopaminergic control of intermediate lobe function in some vertebrates, apomorphine strongly repressed PA synthesis in intermediate, but not anterior lobe cultures.

Adrenocorticotropic Hormone↗
PubMed1996

Histopathological changes in the pituitary glands of female hamsters infected with the 139H strain of scrapie.

Previous studies in hamsters showed that the 139H strain of scrapie injected intracerebrally caused a generalized endocrinopathy and marked hypoglycaemia and hyperinsulinaemia. The low scrapie infectivity levels in the pancreas suggested that the changes noted in that organ were of neuroendocrine origin. In the current study, female weanling Syrian hamsters were inoculated intracerebrally with scrapie strain 139H or 263K, or with homogenate of normal hamster brain. Coronal sections of the pituitary gland were stained with haematoxylin and eosin, Gomori's one-step trichrome, Congo red, thioflavin-S, and antibodies specific for several pituitary hormones. Sections were examined by light microscopy. The hamsters inoculated with scrapie strain 139H showed extensive pituitary vacuolization. Most vacuoles were located in the ventral or ventrolateral parts of the pars distalis. The pituitary glands of 139H-infected hamsters also showed cellular changes, namely, hypertrophy, atrophy and cytoplasmic vesicles. Nuclear changes such as swelling, vesicle formation, chromatin increase, pyknosis, karyorrhexis and karyolysis also occurred. The cellular and nuclear changes were most pronounced in the regions with vacuolation. Hamsters infected with the 263K strain did not show these changes. Immunocytochemical examination suggested that parenchymal cell types which produce different hormones were affected in areas of vacuolation. The changes produced by 139H were not seen in hamsters infected with strain 263K. This study provides the first evidence of cytopathological changes in the pituitary glands of scrapie-infected animals and suggests a relationship between the pituitary changes and the pathological findings in the pancreas and other endocrine organs of 139H-infected hamsters.

Animals↗
PubMed2001

High signal intensity of the posterior pituitary gland on T1-weighted MR images. Correlation with plasma vasopressin concentration to water deprivation.

PURPOSE: To evaluate the effect of water deprivation on the signal intensity of the posterior pituitary gland on T1-weighted MR images and correlate the signal intensity with the plasma vasopressin concentration. MATERIAL AND METHODS: Fifteen rabbits were studied: Group 1 (n=10) was deprived of water for 9 days and Group 2 (n=5) was replenished water for 7 days after 7-day water deprivation. MR imaging and plasma vasopressin measurement by radioimmunoassay were made before and after water deprivation and replenishment. Sequential changes of the signal intensity ratio of the posterior lobe to the pons and plasma vasopressin concentration were correlated. RESULTS: Before water deprivation, the hyperintense posterior lobe was demonstrated in all rabbits. During water deprivation, the signal intensity ratio decreased and vasopressin concentration increased gradually. On the contrary, the signal intensity ratio increased and vasopressin concentration decreased with water replenishment. The signal intensity ratio correlated well with the plasma vasopressin concentration (p<0.05). CONCLUSION: There was a negative, linear correlation between the signal intensity ratio of the posterior pituitary gland on T1-weighted MR images and plasma vasopressin concentration to water deprivation. The results support that the high signal intensity of the posterior pituitary gland on T1-weighted MR images is attributed to the normal content of vasopressin-neurosecretory granules.

Animals↗
PubMed2000

Glial cell line-derived neurotrophic factor in the rat pituitary gland.

The presence of glial cell line-derived neurotrophic factor (GDNF) is described within specific regions of the adult rat pituitary gland. Immune staining methods revealed a small number of GDNF-immunopositive cells in the anterior lobe, and in areas of the neural lobe, while no immunoreactive endocrine cells were observed in the intermediate lobe. In the neural lobe, immunofluorescence methods were also used to demonstrate that GDNF and glial fibrillary acidic protein (GFAP) are co-localized in the glial cells (pituicytes) of the neural lobe. GDNF was not co-localized with neurofilament (NF) in nerve fibers of the neural lobe, suggesting that it is not present in axonal fibers. Measurements of GDNF content in separated anterior and neurointermediate lobes were also performed, using an enzyme-linked immunoassay (ELISA). Values for GDNF were slightly higher in the neurointermediate lobe than those obtained for the anterior lobe. The presence of GDNF in areas of the pituitary is discussed in the context of its possible function to support and maintain hypothalamic innervation, as well as a potential autocrine factor within endocrine cells.

Animals↗
PubMed1983

Cyproheptadine and desmethylcyproheptadine directly inhibit the release of adrenocorticotrophin and beta-lipotrophin/beta-endorphin activity from the neurointermediate lobe of the rat pituitary gland.

Cyproheptadine and its metabolite desmethylcyproheptadine were shown to suppress directly the release of adrenocorticotrophin (ACTH) and beta-lipotrophin/beta-endorphin activity from the neurointermediate lobe of the pituitary gland incubated in vitro. Neither compound affected the release of ACTH from the anterior pituitary gland. Serotonin stimulated the release of ACTH and beta-lipotrophin/beta-endorphin activity from the neurointermediate lobe, but did not influence the (desmethyl)cyproheptadine-mediated inhibition of hormone release. These results indicate that serotonin and cyproheptadine affect hormone release by the neurointermediate lobe by a direct action. The effect of cyproheptadine, however, might not be exerted by a serotonin receptor.

Adrenocorticotropic Hormone↗
PubMed1988

Differences in the cyclic nucleotide mediation of luteinizing hormone-releasing hormone action on the rat and hamster anterior pituitary gland.

A continuous flow superfusion system which was previously developed in our laboratory was utilized to study the modulation of LH and FSH release by cyclic nucleotides and LHRH from anterior pituitary glands (APG) obtained from rats or hamsters. There was a transient increase in LH and FSH secretion from superfused rat APG in response to superfusion with 1 X 10(-3) M 1-methyl-3-isobutyl-xanthine (MIX), while 1 X 10(-4) MIX M had no effect. Furthermore, a dose of 5 X 10(-5) M MIX did not potentiate the gonadotrophin-releasing effect of 1 X 10(-10) M LHRH. Neither 1 X 10(-3) M 8-Br-cAMP nor 1 X 10(-3) M 8-Br-cGMP mimicked the gonadotrophin-releasing effects of 1 X 10(-9) M LHRH. In the experiments utilizing hamster APG, FSH release gradually increased during superfusion with 1 X 10(-3) M MIX or 1 X 10(-4) M MIX, while LH release was transient but significantly increased in response to superfusion with both doses of MIX. A dose of 5 X 10(-5) M MIX potentiated the effect of a low dose of LHRH (1 X 10(-10) M) upon both LH and FSH secretion. 1 X 10(-3) M 8-Br-cAMP mimicked the effect of LHRH upon LH and FSH released from superfused hamster APG, while 1 X 10(-3) M 8-Br-cGMP was inhibitory. These results suggest that cyclic nucleotides are involved in the mediation of the LHRH-induced release of gonadotropins from the anterior pituitary gland of the hamster, but do not mediate the LHRH-induced release of gonadotropins from the rat anterior pituitary gland.

1-Methyl-3-isobutylxanthine↗
PubMed2003

Cloning of a proopiomelanocortin cDNA from the pituitary gland of the sea bass (Dicentrarchus labrax) and assessment of mRNA expression in different tissues by means of real-time PCR.

Proopiomelanocortin (POMC) cDNA was cloned from sea bass (Dicentrarchus labrax) pituitary gland. A 743 nucleotide sequence was obtained coding for the following sequences flanked by sets of proteolytic cleavage sites: ACTH (Ser(88)-Met(127)), alpha-MSH (Ser(88)-Gly(102)), CLIP (Pro(106)-Met(127)), beta-LPH (Glu(131)-Gln(208)), gamma-LPH (Glu(131)-Ser(175)), beta-MSH (Asp(159)-Ser(175)), and beta-endorphin (Tyr(178)-Gln(208)). No region homologous to gamma-MSH/joining peptide (a tetrapod POMC feature) was found. Amino acid sequence identity was high with other teleostean species considered (tilapia: 73%) and lower with elasmobranchs (dogfish: 42%). However, the presumed biologically active peptides were highly conserved within all species considered: alpha-MSH (93-100%), ACTH (80-95%) and beta-endorphin (54-90%). Real-time PCR allowed us to quantify the expression of the POMC in different tIssues of the sea bass: pituitary gland, liver, gonad and head kidney. No significant POMC expression was found in the integument. In pituitary gland, gonads, head kidney and liver, POMC expression was respectively, 1.26x10(10), 2.67x10(5), 2.06x10(4) and 1.67x10(4) copies/ micro g mRNA.

Amino Acid Sequence↗
PubMed1975

[Ultrastructure of the prolactin cells of the pituitary gland of female rats after stimulation with norethisterone enanthate].

Prolactine cells of rat anterior pituitary gland were studied with the electron microscope in thin sections and freeze-etch replicas after treatment with norethisterone-oenanthate. A pathological secretory process is caused in this cell type in rats, when treated with this compound. Prolactine cells grow in number and volume of single cells. This is especially due to an enormous proliferation of the Golgi apparatus. In the same time, however, exocytosis of hormonal secretory granules is apparently reduced. Therefore, serum hormone level remains nearly normal.

Animals↗
PubMed1981

Recovery of the pituitary gland from LRH-induced refractoriness to LRH in the ovariectomized rat.

Recovery of the pituitary gland from LRH-induced refractoriness to LRH was studied in 5-weeks ovariectomized rats. Rats first received over a period of 48 h an infusion of LRH at a rate of 416 ng/h. After discontinuation of this infusion pituitary LH content had decreased to about 50% of its original value and the rate of LH secretion decreased markedly. Over a period of 72 h after discontinuation of the infusion plasma LH values rose to pre-infusion values but pituitary LH content showed such a recovery only partly. In another series of experiments a second infusion of LRH was given during 24 h and again at a rate of 416 ng/h, starting 3, 12, 24 or 72 h after discontinuation of the first infusion. It induced rises of LH secretion which were smaller than those following the first infusion, indicating refractoriness of the pituitary gland to LRH. However, the LH responses became progressively larger with increasing time intervals after the end of the first infusion. This stimulation of LH release was accompanied by a further decrease of pituitary LH content which was still depressed after the first infusion. Comparison of plasma LH levels and pituitary LH content indicated that pituitary responsiveness to LRH can recover independently from pituitary LH content. It can also be concluded that the absolute value of the blood LRH concentration can not be the sole determining factor of LH secretion.

Animals↗
PubMed1992

Quantification of vasoactive intestinal peptide immunoreactivity in the anterior pituitary glands of intact male and female, ovariectomized, and estradiol benzoate-treated rats.

There are considerable data suggesting that vasoactive intestinal peptide (VIP) is involved in the regulation of PRL secretion; however, the role and cell of origin of anterior pituitary VIP remain to be determined. Immunocytochemical (ICC) studies have generally failed to detect VIP-immunoreactive (IR) cells in the pituitary of the untreated rat, although VIP-IR cells have been observed in the pituitaries of hypothyroid or estrogen-treated rats. This study was designed to examine the cellular distribution and tissue content of VIP in the anterior pituitary gland of rats under selected endocrine conditions known to alter the rates of PRL and VIP synthesis and secretion. To this end, anterior pituitary VIP and PRL content (ICC and RIA) and serum PRL levels were determined in ovariectomized (OVX) and OVX rats 3 days after treatment with 7 or 70 micrograms estradiol benzoate (EB). For comparison, pituitary VIP and PRL content (ICC and RIA) and serum PRL levels in untreated male and diestrous female rats were determined. Immunostaining for VIP was accomplished using a newly developed primary antiserum. Significant numbers of VIP-IR cells per 5-microns section were found in the anterior pituitary glands of all animals examined (275 +/- 33 in diestrous to 481 +/- 103 cells in male rats). VIP was not colocalized with PRL in any of the pituitaries regardless of steroid treatment or sex. Furthermore, the number of VIP-IR cells per pituitary gland was not significantly correlated with sex or EB treatment. Treatment with 70 micrograms, but not 7 micrograms, EB significantly increased the pituitary content of VIP and serum PRL levels compared to those after ovariectomy. However, both EB treatments resulted in a significant increase in pituitary PRL content compared to that in untreated OVX rats. Pituitaries from male rats had several-fold more VIP and less PRL content than pituitaries from diestrous rats. These data show that 1) in contrast to previous ICC studies, VIP-IR cells are readily detected in the anterior pituitary of intact male and female and OVX as well as EB-treated rats; 2) VIP is localized to cells other than lactotrophs, regardless of the steroid background; and 3) marked changes in anterior pituitary VIP content are not accompanied by changes in VIP-IR cell number.

Animals↗
PubMed1995

Periventricular-hypophysial dopaminergic neurons innervate the intermediate but not the neural lobe of the rat pituitary gland.

The purpose of the present study was to determine the relative distribution of axon terminals of A14 periventricular-hypophysial dopaminergic (PHDA) neurons in the neural and intermediate lobes of the rat pituitary gland. Discrete unilateral injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) into the periventricular nucleus resulted in labelling of extensively branched terminal axonal arbors in the intermediate lobe, but not the neural lobe of the pituitary gland. In contrast, unilateral injections of PHA-L into the paraventricular nucleus revealed thick, varicose terminal arborizations containing PHA-L in the neural lobe, but not the intermediate lobe. Terminal axonal branches and varicosities containing PHA-L immunoreactivity in the intermediate lobe were also immunoreactive for tyrosine hydroxylase. These results reveal that A14 PHDA neurons originating in the periventricular nucleus of the hypothalamus project axons to the intermediate lobe of the rat pituitary gland.

Animals↗
PubMed1996

Calcified concretions in the anterior pituitary gland of the fetus and the newborn: a light and electron microscopic study.

Calcified concretions including typical laminated psammoma bodies can be detected on routine hematoxylin-eosin (H&E) examination of fetal and neonatal anterior pituitary glands. This finding has seldom been reported in the literature and, to the authors' knowledge, no ultrastructural examinations of fetal or neonatal pituitary calcifications have been reported to date. In this study, histological sections of anterior pituitary glands from 200 fetuses and infants ranging in age from 15 weeks of gestation to 1 year of life revealed calcified concretions in all the cases up to 1 month of life. They decreased in incidence postnatally and were not found after 6 months of age. Most were round to ovoid, basophilic or eosinophilic, often laminated, and measured between 5 and 30 microm in diameter. Immunohistochemical stains showed that the calcifications followed no particular pattern of distribution among the most prevalent pituitary cell types. Ultrastructural examination revealed small single or multiple intracellular calcified deposits, and larger, sometimes laminated, extracellular calcifications, suggesting an intracellular origin for the concretions with cell death occurring concomitant with their formation. This phenomenon, which to some extent resembles the formation of psammoma bodies in certain tumors, seems to represent a distinctive morphological type of developmental cell death. Apoptosis, a more common form of developmental cell death, was also found in some of the sections. Pathologists should be aware of the fact that calcified concretions represent a normal finding in the anterior pituitary gland of fetuses and young infants. Their mere presence in cases of fetal or perinatal demise with no other pertinent findings should not be attributed to intrauterine viral infections or ischemic-anoxic events.

Calcification, Physiologic↗
PubMed1989

[Morphological studies on estrogen-induced PRL cell hyperplasia in rat pituitary gland--immunocytochemical and scanning electron microscopic studies].

It is well known that the tumorous lesion in rat anterior pituitary gland occurs after continuous administration of estrogen, which is mainly composed of PRL secreting cells. In this study the changes in rat PRL cells by estrogen treatment were studied histologically and immunocytochemically. Furthermore, intracellular structures in PRL cells were observed by high resolution scanning electron microscopy using the aldehyde prefix osmium-DMSO-osmium method. These rat pituitary tumors were established in Fischer-344 female rats by weekly injections of 2.5 mg estradiol valerate. The estrogen-induced, autonomous and transplantable rat pituitary tumors (MtT/F84) were also studied in the same manner and the findings were compared with estrogen-induced tumors. The increase of weight of pituitary gland and of serum PRL level correlated significantly with the number of estrogen administration. On the basis of histological findings, estrogen-induced pituitary tumors can be classified into two different stages, that is, hypertrophic hyperplasia and adenomatous hyperplasia. The former corresponds to the period until 6 weeks after the beginning of estrogen treatment and the latter to the period thereafter. In the former, PRL cells were significantly increased in number and volume, and were diffusely immunoreactive for PRL in the cytoplasm. Cell atypism was rarely found. The extent of acidophil staining was well preserved in hematoxylin-eosin staining. Ultrastructurally, organelles were well developed, especially rough endoplasmic reticulum showed whorl formation. Immature, irregularly shaped secretory granules were frequently observed within the Golgi area. Mature granules were richly stored at the periphery of the cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Molecular components of the exocytotic machinery in the rat pituitary gland.

Several protein components that are essential for exocytotic membrane fusion in neurons have recently been identified. The expression and cellular localization of such protein components were examined in the rat pituitary gland. In situ hybridization using isoform-specific oligonucleotide probes to different exocytotic protein messenger RNAs (mRNAs) showed strong hybridization signal for synaptotagmin I, cysteine string protein (CSP), VAMP-2 (vesicle-associated membrane protein), cellubrevin, munc-18 (mammalian homologue of unc-18), SNAP-25a (synaptosomal-associated protein of 25 kDa), syntaxin 1A, syntaxin 4, syntaxin 5, and alpha-SNAP (soluble NSF attachment protein) in the anterior and intermediate, but not in the posterior lobe of the pituitary. Moderate to weak hybridization signal was detected for synaptotagmin III, SNAP-25b, and syntaxin 2 mRNA in the anterior and intermediate, but not in the posterior lobe of the pituitary. Synaptotagmin II, VAMP-1, syntaxin 1B, or syntaxin 3 mRNA expression could not be detected in any part of the pituitary gland. Immunofluorescence histochemistry in combination with confocal laser microscopy revealed that synaptotagmin-, VAMP-, CSP-, NSF-, and alpha-SNAP-like immunoreactivities (-LI) were present in granules of cells in the anterior and intermediate lobe, whereas SNAP-25- and syntaxin-LI were primarily located to the plasma membrane. Synaptotagmin-, VAMP-, CSP-, NSF-, alpha-SNAP-, SNAP-25- and syntaxin-LI were all present in nerve fibers of the posterior lobe. Within cells of the anterior lobe, colocalization could be demonstrated for synaptotagmin I/II- and synaptotagmin III-LI with ACTH-, GH-, PRL- and TSH-, but not FSH- or LH-LI, whereas VAMP, CSP-, NSF-, alpha-SNAP-, SNAP-25- and syntaxin-LI were demonstrated in all hormone-containing cell types of the anterior pituitary. The results show the presence of several protein components and their isoform-specific mRNAs in the rat pituitary gland, suggesting that these proteins, similar to their roles in regulation of synaptic neurotransmitter release, may participate in exocytotic events in endocrine pituitary cells and in neurosecretory nerve endings of the neurohypophysis.

Animals↗