Effect of hypophysectomy on hypothalamic somatostatin content in rats.

Wakabayashi, Ichiji; Demura, Reiko; Kanda, Mitsuro; Demura, Hiroshi; Shizume, Kazuo

doi:10.1507/endocrj1954.23.439

Cited by 25 publications

(9 citation statements)

References 7 publications

(10 reference statements)

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“…Our results confirm the decrease in SS content with hypo physectomy observed in other studies [13,14,16,18]. The ab sence of an increase of hypothalamic SS content in our studies with supraphysiologic and replacement GH administration de spite weight gain differs with other published studies [16,18], but is in agreement with a preliminary study [39], It is not clear what experimental factors are responsible for the different re sults observed, but technical aspects that differ from previous studies, e.g.…”

Section: Discussionsupporting

confidence: 90%

Effect of Hypophysectomy and Growth Hormone Administration on Hypothalamic Growth Hormone-Releasing Hormone and Somatostatin Content: Relationship to Age-Related Growth Rate

Leidy

McDermott

Robbins³

1990

Neuroendocrinology

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The purpose of these studies was to evaluate the effect of age-related differences in growth rate on the hypothalamic content of growth hormone-releasing factor (GHRH) and somatostatin (SS) and on the short loop feedback regulation of GHRH and SS. Percent weight gain, GHRH content, and SS content in control adolescent (8 weeks) and adult rats (6 months) were compared in normal rats administered supraphysiologic amounts of rat growth hormone (rGH) or in hypophysectomized rats receiving thyroxine and corticosterone with or without physiologic rGH replacement. In control adolescent rats, the rate of weight gain was 5-fold higher than in adult rats. GHRH content was higher in adolescent rats, while SS content was lower. After the administration of supraphysiologic amounts of rGH, GHRH content increased in adolescent rats but did not change in adult rats. SS content was unchanged in either age group. Following hypophysectomy GHRH content declined similarly in both groups, whereas the decrease in SS content was greater in adolescent rats. With replacement rGH, weight gain was restored, GHRH content increased but not fully to control, and SS content did not change. The ratio of SS content to GHRH content (SS/GHRH) was higher in control adult rats than in adolescent rats. SS/GHRH increased following hypophysectomy and returned to control values by rGH replacement. We conclude that age-related differences in growth rate are accompanied by appropriate changes in SS/GHRH and that SS and GHRH are regulated by short loop feedback at both ages with increased responses in adolescent rats. The inability of thyroxine, corticosterone, and rGH replacement to fully restore GHRH and SS content after hypophysectomy suggest that other factors contribute to the regulation of hypothalamic GHRH and SS.

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Section: Discussionsupporting

confidence: 90%

Effect of Hypophysectomy and Growth Hormone Administration on Hypothalamic Growth Hormone-Releasing Hormone and Somatostatin Content: Relationship to Age-Related Growth Rate

Leidy

McDermott

Robbins³

1990

Neuroendocrinology

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“…Somatostatin may par ticipate in this feedback mechanism. Evidence is that GH increases hypothalamic concentrations of somatostatin and stimulates the secretion of somatostatin from cultured hy pothalamic block incubates [4], hypophysectomy dimin ishes somatostatin concentrations in median eminence and PO/AHA [4,31,34], and intracerebroventricular injection of GH stimulates somatostatin release into the portal blood [8]. It is possible therefore that the more frequent GH bursts in lesioned animals might reflect interrupted GH negative feedback, though there must be an additional disturbance to account for reduced average GH concentrations.…”

Section: Discussionmentioning

confidence: 99%

Evidence That the Regulation of Growth Hormone Secretion Is Mediated Predominantly by a Growth Hormone Releasing Factor

et al. 1983

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Spontaneous pulsatile growth hormone (GH) secretion and stress-induced suppression of GH was examined in chronically cannulated male rats with electrolytic lesions of the periventricular preoptic anterior hypothalamic area (PO/AHA) where somatostatin neurons innervating the median eminence are known to be located. Median eminence somatostatin was depleted in lesioned animals by 85%. Bursts of GH secretion occurred more frequently than in sham-lesioned animals (1.9 ± 0.2 vs. 2.6 ± 0.2 h, respectively, p < 0.025), however, average concentrations of GH were reduced by lesions (118.4 ± 11.6 vs. 192.3 ± 28.4 ng/ml, p < 0.025). Suppression of GH by stress was unaffected by PO/AHA lesions. It is concluded that somatostatin plays only minor roles in the generation of GH troughs during rhythmic GH secretion, and in the suppression of GH during stress. Inhibition of GH releasing factor secretion, therefore, is presumed to be the likely method by which GH suppression is achieved in these physiological situations.

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“…Baker et al [3], using the immunohistochemical technique, ex plained that depletion of SRIF from the me dian eminence might be due to the degenera tion and subsequent repair after hypophysec tomy. Wakabayashi et al [14], using radio immunoassay, indicated that the elimination of feedback actions of GH and/or TSH on the hypothalamus might lead to decreased synthesis and/or release of SRIF but could not rule out the possibility that structural changes after operation resulted in the deple tion of SRIF.…”

Section: Discussionmentioning

confidence: 99%

“…Examinations of the effect of hypophysec tomy on SRIF content in the median emi nence have been performed and demonstrated that SRIF content decreased following sur gery. The probability that the hypothalamic SRIF depends on feedback by the pituitary growth hormone has been indicated but the possibility that trauma and the resultant re pair of the tissue by hypophysectomy also in fluences the content of SRIF cannot be ruled out [3,14]. The present study was undertaken…”

mentioning

confidence: 96%

Effect of Hypophysectomy and Growth Hormone Administration on Somatostatin Content in the Rat Hypothalamus

et al. 1979

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The effect of hypophysectomy and bovine GH administration on somatostatin (SRIF) content in the rat hypothalamus was investigated. SRIF content was determined by a specific radioimmunoassay method described elsewhere. The total SRIF content of the rat hypothalamus as well as its content per milligram wet weight had decreased 4 weeks after hypophysectomy but was restored significantly in those rats which were subjected to bovine GH administration for 7 days 3 weeks after hypophysectomy. Furthermore, in nonoperated rats, increase of hypothalamic SRIF content was observed after 7 days GH administration. These results indicate that growth hormone may influence the SRIF content of hypothalamus and it seems likely that a feedback mechanism between pituitary GH and hypothalamic SRIF exists.

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Effect of hypophysectomy on hypothalamic somatostatin content in rats.

Cited by 25 publications

References 7 publications

Effect of Hypophysectomy and Growth Hormone Administration on Hypothalamic Growth Hormone-Releasing Hormone and Somatostatin Content: Relationship to Age-Related Growth Rate

Effect of Hypophysectomy and Growth Hormone Administration on Hypothalamic Growth Hormone-Releasing Hormone and Somatostatin Content: Relationship to Age-Related Growth Rate

Evidence That the Regulation of Growth Hormone Secretion Is Mediated Predominantly by a Growth Hormone Releasing Factor

Effect of Hypophysectomy and Growth Hormone Administration on Somatostatin Content in the Rat Hypothalamus

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