In vivo and in vitro studies on the release of cortisol from interrenal tissue in trout. I. Effects of ACTH and prostaglandins.

The secretion of cortisol from the interrenal tissue in trout Salmo gairdnerii was studied in vivo and by an in vitro superfusion method in relation to the effect of adrenocorticotropic hormone (ACTH), prostaglandins (PGE1, PGF2 alpha) and prostaglandin inhibitors. The experiments were performed between April and July. In control, uninjected animals, circulating cortisol was 206 +/- 24 ng/ml. At 24 h following the intraperitoneal injection of indomethacin, dexamethasone, or both, the levels were reduced to 84 +/- 10, 43 +/- 20 and 63 +/- 11 ng/ml respectively. In control animals receiving solvent (ethanol), the value was 190 +/- 30. With longer term duration (72 h) the levels of plasma cortisol following injection of indomethacin, dexamethasone and both drugs together were 120 +/- 29, 120 +/- 10 and 37 +/- 8 respectively. On the contrary, no significant change was produced by prostaglandins. In vitro release of cortisol from superfused head kidneys (which contain the interrenal tissue of teleosts) decreased gradually with time and reached a minimum after 50 min. Addition of ACTH or of PGE1 to the medium induced an immediate, dose dependent increase in cortisol output which reached a maximum after 15-30 min. On the contrary, PGE2 alpha or indomethacin did not modify cortisol release. These results show that cortisol production in trout, which is controlled by ACTH as in other vertebrates, is also under the influence of other hormonal substances acting on the adenyl-cyclase system.