[In vitro somatostatin secretion from the median eminence and the neurohypophysis].
The mechanisms of somatostatin secretion from nerve endings were investigated using the rat median eminence and neurohypophysis in vitro. Determination of total immunoreactive somatostatin content yielded: 36 +/- 2,7 ng per median eminence and 0,74 +/- 0,09 ng per neural lobe. Upon increasing the external potassium concentration a significant rise in somatostatin release from both tissues was observed. (Neural lobe: from 0,86% to 7,4%, median eminence: from 0,09% to 0,47% of total content per 30 minutes). A significant increase in hormone output was also observed following electrical stimulation. The secretory response was abolished whenever external calcium was omitted or replaced by manganese. It is concluded that somatostatin secretion from median eminence and neural lobe in vitro shows two characteristics typical of a neurosecretory process: release upon membrane depolarization and dependence of this process on external calcium.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004558:Electric Stimulation; D005260:Female; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism*; D008297:Male; D008345:Manganese / Q000494:pharmacology; D008473:Median Eminence / Q000378:metabolism*; D009411:Nerve Endings / Q000378:metabolism; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D013004:Somatostatin / Q000378:metabolism*
D008345:Manganese; D013004:Somatostatin; D011188:Potassium; D002118:Calcium
Sécrétion de somatostatine à partir de l'éminence médiane et de la posthypophyse in vitro.