SYNTHESIS AND SECRETION OF A LARGE GLYCOPROTEIN IN THE PARS INTERMEDIA

1975 ◽  
Vol 65 (2) ◽  
pp. 225-231 ◽  
Author(s):  
C. R. HOPKINS
Keyword(s):  
Molecular Weight ◽  
Xenopus Laevis ◽  
Intracellular Transport ◽  
Pars Intermedia ◽  
Secretory Product ◽  
Melanocyte Stimulating Hormone ◽  
Leucine Residue ◽  
Large Molecular Weight ◽  
Stimulating Hormone

SUMMARY The biosynthesis, intracellular transport and release of [3H]leucine-containing secretory product has been followed in the pars intermedia of Xenopus laevis and, in particular, the synthesis and secretion of a large molecular weight glycoprotein secretory product was demonstrated. However, if Xenopus adrenocorticotrophin does contain a leucine residue the results obtained provided no support for the view that it serves as a precursor for melanocyte-stimulating hormone in this species.

THE EFFECT OF INGESTION OF HYPERTONIC SALINE ON THE MELANOCYTE-STIMULATING HORMONE CONTENT AND HISTOLOGY OF THE PARS INTERMEDIA OF THE RAT PITUITARY GLAND

1970 ◽  
Vol 46 (2) ◽  
pp. 201-NP ◽  
Author(s):  
A. HOWE ◽  
A. J. THODY
Keyword(s):  
Control Level ◽  
Pars Intermedia ◽  
Type I ◽  
Melanocyte Stimulating Hormone ◽  
Level Of Activity ◽  
Numerous Type ◽  
Rat Pituitary ◽  
Stimulating Hormone

SUMMARY The changes in the content of melanocyte-stimulating hormone (MSH) and histology of the neuro-intermediate (n.i.) lobe were followed in rats which drank 2% sodium chloride for periods from 1–15 days. The pars intermedia showed a biphasic response. During the initial phase of 1–4 days there was a rapid rise in the MSH content, by 153% in the first day, falling back to control level by 4 days. These fluctuations were paralleled by an increase in the normally small numbers of Type 2 cells and at the same time numerous Type I cells showed hypertrophy and degranulation. After 4 days on saline there was a second rise in the MSH content, which was still evident at 15 days; during this second period the number of Type 2 cells declined to normal levels. The degranulated Type 1 cells also disappeared, most of Type 1 being smaller in size and intensely PAS-positive. After the ingestion of saline it apparently takes several days before the pars intermedia adapts to a new level of activity. The likely significance of these changes and the possibility of a relationship between the pars intermedia and the neurohypophysis are discussed.

Seasonal and photoperiod-induced changes in the secretion of α-melanocyte-stimulating hormone in Soay sheep: temporal relationships with changes in β-endorphin, prolactin, follicle-stimulating hormone, activity of the gonads and growth of wool and horns

1995 ◽  
Vol 144 (3) ◽  
pp. 471-481 ◽  
Author(s):  
G A Lincoln ◽  
B I Baker
Keyword(s):  
Blood Plasma ◽  
Follicle Stimulating Hormone ◽  
Plasma Concentrations ◽  
Fold Increase ◽  
Molar Ratio ◽  
Pars Intermedia ◽  
Soay Sheep ◽  
Melanocyte Stimulating Hormone ◽  
Short Days ◽  
Stimulating Hormone

Abstract Blood plasma concentrations of α-melanocyte-stimulating hormone (α-MSH), β-endorphin (β-END), prolactin and follicle-stimulating hormone (FSH), and associated changes in the size of the testes, and growth of the horns and pelage were measured in male (n=8), castrated male (n=5) and female (n=9) Soay sheep. The animals were born in April and kept outdoors near Edinburgh (56 °N) during the first two years of life. In all groups there was a close association between the weekly changes in the plasma concentrations of α-MSH and β-END; the molar ratio in mean concentrations was close to 1:1. The blood plasma concentrations of both hormones varied markedly with season with a 3- to 10-fold increase in concentrations from the minimum in winter to the maximum in autumn. The seasonal peak occurred in September in the first year of life as juveniles, and between July (males) and September (females) in the second year when the animals were sexually mature. The plasma concentrations of ACTH did not vary in parallel with the seasonal changes in the concentrations of α-MSH (measured only in males); the molar ratio for the concentrations of α-MSH:ACTH was 1:0·12. The seasonal increase in the concentrations of α-MSH occurred 1–3 months after the seasonal increase in the concentrations of prolactin and the associated growth in horns and pelage, and slightly before, or coincident with the seasonal increase in the concentrations of FSH and the growth in the testes. In a second experiment, the same parameters were measured in a group of adult male Soay sheep (n=8) housed indoors under an artificial lighting regimen of alternating 16-week periods of long (16 h light:8 h darkness) and short days (8 h light:16 h darkness). In this situation, there was a clearly defined photoperiod-induced cycle in the plasma concentrations of α-MSH with a 25-fold increase from a minimum under long days to a maximum under short days. The concentrations of β-END varied in close parallel with the changes in α-MSH, and the temporal associations with the changes in the other pituitary hormones were similar to those observed in animals housed outdoors. Overall, the results support the view that α-MSH is co-secreted with β-END from the melanotrophs in the pars intermedia of the pituitary gland, and that the secretory activity of the melanotrophs changes markedly with season, increasing in summer and autumn, and decreasing in winter and spring. The annual cycle in daylength is likely to be the principle environmental cue timing the cycle in α-MSH and β-END. α-MSH is known to have biological effects in the brain (neuroendocrine control of prolactin and FSH), and in the adrenal gland (secretion of glucocorticoids), adipose tissue (fat storage), and skin (melanogenesis and secretion of sebum). Thus the seasonal increase in the secretion of α-MSH may regulate multiple physiological changes in autumn in preparation for winter. Journal of Endocrinology (1995) 144, 471–481

scholarly journals Cytological Differences in the Localization of Glucocorticoid Receptor-Like Imnunoreactivity in the Normal and Transplanted Pituitary Pars Intermedia

1992 ◽  
Vol 3 (1) ◽  
pp. 35-38 ◽  
Author(s):  
Fermlín C. Iturriza ◽  
César L. A. Gómez Dumm
Keyword(s):  
Glucocorticoid Receptor ◽  
The Other ◽  
Pars Intermedia ◽  
Dark Cells ◽  
Melanocyte Stimulating Hormone ◽  
Patterns Of Distribution ◽  
Other Hand ◽  
Light Cells ◽  
Stimulating Hormone

Glucocorticoid receptor-like immunoreactivity (GCRI) was found in the normal pituitary pars intermedia (PI) when immunohistochemistry was used. Since in previous studies we described two kinds of cells in the denervated (grafted) PI, i.e., “light cells” (overactive cells which do not contain detectable melanocyte stimulating hormone) and “dark cells” (hypoactive cells which contain the hormone), it was decided to investigate whether different patterns of distribution of the receptors could be detected in the grafted gland when compared with the intact PI. Intact glands showed the receptors located in the nucleus. In transplanted glands, it was observed that light cells showed receptors in both the nuclei and the cytoplasm; on the other hand, dark cells displayed them in the nuclei only, as is the case in all cells of the normal PI.We had previously interpreted dark cells as dopamine-indifferent, whereas light cells were considered dopamine-sensitive. The changes in the distribution of GCR after denervation by grafting, which only affected the light cells, support the view of other authors that GCR of. the pars intermedia are under the influence of dopamine and reinforce our opinion that dark cells are dopamine-indifferent

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