Actions of somatostatin on perfused bovine adrenal glands and cultured bovine adrenal medullary cells

Abstract

The effects of somatostatin on catecholamine secretion and inositol phosphate accumulation have been studied using isolated perfused bovine adrenal glands and cultured bovine adrenal medullary cells. Somatostatin had no effect on basal adrenaline or noradrenaline secretion from either preparation. At concentrations above 1 μM, somatostatin inhibited the secretion of both catecholamines induced by 5 μM nicotine from cultured chromaffin cells. In contrast, over the concentration range 0.1 nM–10 μM, somatostatin had no effect on the secretory responses produced by 10 nM angiotensin II or 1 μM histamine. Inositol phosphate accumulation in cultured bovine adrenal medullary cells was unaffected by 0.1 nM–0.1 μM somatostatin, however at 1 and 10 μM somatostatin it was significantly increased, by 2% and 103% respectively. The effects of somatostatin (0.1 nM–10 μM) and of 50 μM muscarine on inositol phosphate accumulation were simply additive. Similarly, somatostatin at 0.1 nM and 10 nM together with 10 nM angiotensin II or 1 μM histamine produced additive inositol phosphate responses. In contrast, 1 μM somatostain gave significantly more-than-additive (synergistic) inositol phosphate responses with angiotensin II and histamine. The results suggest that some adrenal medullary cells possess several types of receptors, and that these receptors may interact to produce non-additive responses.