MECHANISMS OF ACTH-STIMULATED AND ANGIOTENSIN-II-STIMULATED 1-ALPHA-HYDROXYCORTICOSTERONE SECRETION IN THE DOGFISH, SCYLIORHINUS-CANICULA

An isolated perifused interrenal gland preparation from the lesser-spotted dogfish, Scyliorhinus canicula, was used to investigate the mechanisms of action of ACTH and angiotensin II (AII) on elasmo-branch adrenocortical cells. ACTH-stimulated 1alpha-hydroxycorticosterone secretion was unaffected by dantrolene and significantly decreased in the absence of extracellular calcium. Dibutyryl cyclic AMP produced a dose-dependent increase in 1alpha-hydroxycorticosterone secretion. The results suggest that the mechanism of ACTH action in elasmobranchs may be similar to that reported for mammals and amphibians, involving the synergistic action of calcium with the cyclic AMP messenger system. AII-stimulated 1alpha-hydroxycorticosterone secretion was significantly inhibited in the presence of dantrolene and in the absence of extracellular calcium, indicating that both extracellular and intracellular calcium are required for the full action of AII. These results are consistent with results in mammals and amphibians where AII stimulates phosphatidylinositol 4,5-bisphosphate hydrolysis and changes in intracellular calcium concentration, and they suggest that All may operate via this mechanism to stimulate 1alpha-hydroxycorticosterone secretion in elasmobranchs.