REGULATION OF INTERRENAL SECRETION IN THE AXOLOTL, AMBYSTOMA-MEXICANUM

The regulation of corticosteroid secretion of the adrenal cortex (inte rrenal tissue) of axolotl (Ambystoma mexicanum) was studied using in v itro preparations of kidney containing interrenal tissue. Normally, 0. 3-0.65 ng/5 min corticosterone and 0.15-0.3 ng/5 min aldosterone were released from the tissue. Regulatory peptides were effective in the fo llowing range: ACTH = arginine vasotocin > urotensin II > angiotensin II. They stimulate an elevation of corticosterone (plus 0.2-1 ng/5 min ) and of aldosterone (plus 0.05-0.15 ng/5 min). The three primary effe ctor systems leading to second messengers, adenylate cyclase (forming cAMP), phospholipase C (forming InsP(3) + DAG), and phospholipase A(2) (liberating arachidonic acid) are involved in stimulation of biosynth esis. It can be suggested that the second messengers stimulate the bio synthesis at the level of the steps between pregnenolone and corticost erone ('3 beta-hydroxysteroid-dehydrogenase etc.), because the release of corticosterone is more stimulated than aldosterone. This is differ ent than the regulation of anuran interrenal tissue. Ca++ ions are inv olved in corticosterone secretion. Verapamil inhibits immediately the secretion of corticosteroids and elevation of external Ca++ stimulates the release. It is suggested that Ca++ mediates the secretion process itself. Metamorphosis does not change the response of the interrenal gland compared with the neotenic animal.