In vitro study of frog ( Rana ridibunda Pallas) interrenal function by use of a simplified perifusion system III. Influence of previous hypophysectomy or dexamethasone treatment of donors upon corticosterone and aldosterone production

Abstract

Effects of long-term hypophysectomy and dexamethasone treatment on interrenal function of Rana ridibunda have been studied in vitro by use of a perifusion system technique. Hypophysectomy significantly reduced secretory activity of interrenal tissue (nearly 60% reduction for both corticosterone and aldosterone biosynthesis) but did not affect interrenal responsiveness to crude homologous pituitary extract and did not modify the ratio aldosterone/corticosterone as well. Daily injections of 1 mg dexamethasone during 20 days diminished both corticosterone and aldosterone productions by interrenal tissue to about 40% of those of glands from normal animals. Dexamethasone treatment did not alter interrenal responsiveness to crude homologous pituitary extract. In addition, daily injections of 0.6% NaCl solution for 18 days (0.25 ml/animal) resulted in a specific decrease in aldosterone secretion. Aldosterone/corticosterone secretion ratios were 2.1 in normal frogs, 2.3 in hypophysectomized frogs, 2.2 in sham-hypophysectomized frogs, and 1.9 in dexamethasone-treated frogs. This ratio fell to 1.3 in saline-treated frogs. These in vitro results are consistent with previous in vivo data on anuran pituitary-interrenal relationships which had demonstrated partial independence of interrenal function from pituitary control. They also provide evidence that alteration of electrolyte balance specifically modifies aldosterone production without significant change in corticosterone biosynthesis.