Stimulation by Synthetic Thyrotropin-Releasing Hormone of Glucose Oxidation in Porcine and Rat Pituitary Slices
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Synthetic TRH stimulated the oxidation of glucose-1-14C to 14CO2 at a concentration of 2.5 μg/ml in porcine anterior pituitary slices. This stimulation was not observed in porcine posterior pituitary slices or in rat hemipituitaries. TRH also stimulated the production of 14CO2 from glucose-U-14C in the porcine anterior pituitary. This stimulatory effect of TRH on glucose oxidation was blocked by thyroxine added to the incubation medium at a concentration of 10 μg/ml.Today much attention is paid to the study of the pituitary ultrastructure of laboratory animals and humans. But there is not enough available literature to study the most important organ of internal secretion of productive animal. The aim of our work is to study the structure of the ultrastructure of cells of the anterior pituitary gland of cattle in the definitive period of postnatal ontogenesis. Histological, morphometric, and electron microscopic techniques were used to study the cellular composition of the anterior pituitary gland of cattle. It was revealed that the anterior lobe of the pituitary gland occupies 64 % of the entire pituitary parenchyma, while the posterior and middle lobes occupy 27% and 9%, respectively. After using general histological methods there are detected the functionally inactive chromophobes (41%) and chromophilic cells, which include acidophils (38%) and basophils (21%) in the anterior lobe of the pituitary gland. The electron microscopic studies in the parenchyma of the anterior pituitary gland let find Somatotropes that differ in the presence of a large number of secretory granules in the cytoplasm. Lactotropes are less common than somatotropes and differ from them in larger secretory granules. Corticotropes, gonadotropes and thyrotropes with a minimum content of secretory granules are the least detected. All identified endocrine cells are at different stages of functional activity.
Thyrotropic cell
Corticotropic cell
Parenchyma
Posterior pituitary
Neuroendocrinology
Endocrine gland
Pars intermedia
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Insulin-like growth factors I and II (IGFI and II) are synthesized by anterior pituitary cells and participate in cellular growth and differentiation, as well as the control of pituitary hormone secretion. Type 1 and 2 IGF receptors (IGFR1 and IGFR2) and the six IGF binding proteins (IGFBPs), which modulate IGF effects, are expressed in the anterior pituitary gland. We used in situ hybridization to analyse the temporal expression pattern of IGFI and II, IGFR1 and 2 and IGFBP1-6 in the anterior pituitary gland during postnatal development in both male and female rats (10, 20, 30, 40 and 60 days of age). We found all of the components of the IGF system to be expressed in the anterior pituitary gland, with each having a specific temporal pattern of expression. In addition, there exist differences between the sexes in the expression of some components of the IGF system. These data emphasize that in the anterior pituitary gland the IGF system is under tight regulation during postnatal life when this gland continues to develop. The distinct temporal expression of each member of the IGF system may indicate specific roles in the development and physiology of the anterior pituitary gland.
Endocrine gland
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The present study was undertaken to determine whether T3 could modify anterior pituitary Ca++ metabolism under basal conditions and in the presence of TRH. Paired hemipituitaries from hypothyroid rats were preincubated with T3 (10-7 M) for 2 h, allowed to accumulate 45Ca++ for the third hour, and repeatedly washed in static incubations or superfused for the next 2 h with isotope-free medium and finally with TRH (10-8 M) for 10 min. T3 treatment had no effect on the basal pattern of isotope loss throughout the 2-h wash period. TRH stimulated 45Ca++ fractional efflux from a basal value of 0.76 ± 0.10% to 1.66 ± 0.38% min-1 (P < 0.02; mean ± SD; n = 9). T3 reduced TRH-stimulated efflux to 1.30 ± 0.20% min-1, while basal values were unaltered (0.70 ± 0.10% min-1). Similarly, T3 inhibited the TSH response to TRH from 480% to 200% of basal secretion. T3 pretreatment also inhibited the basal uptake of 45Ca++ when a La+++ displacement protocol was employed from 1751 ± 36 to 1400 ± 61 cpm/mg pituitary (mean ± SEM; n = 13; P < 0.001). Similar data for 45Ca++ efflux were obtained in experiments where tissue was superfused. rT3 did not affect basal or stimulated 45Ca++ efflux, and inhibition of stimulated secretion and 45Ca++ efflux by T3 was dependent on preincubation. The data indicate that T3 is capable of altering anterior pituitary Ca++ homeostasis. Such a mechanism could be involved in the T3-induced inhibition of TRH-stimulated TSH release which appears to require a redistribution of cellular Ca++. (Endocrinology108: 1690, 1981)
Basal (medicine)
Efflux
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Portions of sheep anterior pituitary lobe tissue were extracted under acid conditions and assayed for the two neurophysins (oN-III and oN-I/II) by radioimmunoassay. In all tissues examined, oN-III and oN-I/II immunoreactivi-ties were detected. Using a combination of isoelectric focusing and polyacrylamide gel electrophoresis, the neurophysins of the anterior pituitary gland behaved like oN-III and oN-I/II. oN-III of the anterior pituitary was purified by affinity chromatography and high-performance liquid chromatography. This corticotroph oN possessed an amino acid analysis similar to that of oN III and an N-terminal amino acid sequence, including residues 1–24, identical to that of authentic oN-III. These findings support the work of others who have identified neurohypophysial hormones in the anterior pituitary gland.
Neurophysins
Corticotropic cell
Pars intermedia
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Abstract Thyrotropin‐releasing hormone (TRH) stimulates prolactin production in cultured GH 3 rat anterior pituitary tumor cells. For correlation of cell‐by‐cell prolactin distribution and intracellular hormone concentration, GH 3 cells were grown to plateau‐phase density on glass coverslips in plastic dishes. Acetone‐fixed, cell‐bearing coverslips were stained for prolactin by an immunoglobulin‐peroxidase bridge technique (Mason et al., '69); cells on the plastic dishes were assayed for prolactin (microcomplement fixation immunoassay, Tashjian, '73) and protein content. Intracellular prolactin, unaffected quantitatively by acetone fixation and choice of substratum, was localized immunocytochemically by a granular brown precipitate, abolished if anti‐prolactin serum was preabsorbed with rat prolactin or omitted from the protocol. Intracellular prolactin was maximized with colchicine (5.0 × 10 −6 M; final 3 hr of incubation) in control and TRH‐treated (10 ng/ml; 48 hr) GH 3 cell cultures. A total of 8,500 cells were classified by light microscopy as unstained, heavily (H) or moderately (M) stained for prolactin. In controls, 35% of cells were prolactin‐positive: 6% H and 29% M. After TRH, 45% were positive: 7% H and 38% M. Although prolactin‐positive cells were unevenly distributed, comprising 25% to 46% of cells in individual microscopic fields in controls, TRH increased the proportion of M cells in all areas. TRH treatment raised prolactin levels to 450% of control, but mathematical analysis attributed less than 30% of the increase to new prolactin‐positive cells. We conclude that TRH acts on GH 3 cultures principally by raising the mean hormone content of individual positive cells rather than by increasing the proportion of cells committed to prolactin production.
Prolactin cell
Thyrotropic cell
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Abstract Insulin‐like growth factors I and II (IGFI and II) are synthesized by anterior pituitary cells and participate in cellular growth and differentiation, as well as the control of pituitary hormone secretion. Type 1 and 2 IGF receptors (IGFR1 and IGFR2) and the six IGF binding proteins (IGFBPs), which modulate IGF effects, are expressed in the anterior pituitary gland. We used in situ hybridization to analyse the temporal expression pattern of IGFI and II, IGFR1 and 2 and IGFBP1–6 in the anterior pituitary gland during postnatal development in both male and female rats (10, 20, 30, 40 and 60 days of age). We found all of the components of the IGF system to be expressed in the anterior pituitary gland, with each having a specific temporal pattern of expression. In addition, there exist differences between the sexes in the expression of some components of the IGF system. These data emphasize that in the anterior pituitary gland the IGF system is under tight regulation during postnatal life when this gland continues to develop. The distinct temporal expression of each member of the IGF system may indicate specific roles in the development and physiology of the anterior pituitary gland.
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The effects of Pro-thyrotropin-releasing hormone (TRH), pre-pro-TRH (53-74), pre-pro-TRH (83-106), pre-pro-TRH (115-151), pre-pro-TRH (160-169), pre-pro-TRH (178-199) and TRH on thyrotropin (TSH) and prolactin (PRL) release from the rat anterior pituitary were studied in vitro. The rat anterior pituitary was incubated in medium 199 (pH 7.4) with 1.0 mg/ml of bacitracin (medium) for 30 min. The amount of TSH and PRL release into the medium was measured by radioimmunassay. TSH and PRL release from the anterior pituitary was stimulated with the addition of TRH or pro-TRH in a dose-related manner, but not with other peptides. The findings suggest that TRH and pro-TRH stimulate TSH and PRL release from the anterior pituitary in vitro.
TRH stimulation test
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Thyrotropic cell
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Endocrine gland
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