In vitro studies on the release of cortisol from interrenal tissue in trout (Salmo gairdneri)--II. Action of changes in extracellular electrolytes.

Secretion of cortisol by the interrenal tissue of the trout Salmo gairdneri was studied in vitro by a perifusion method in relation to the effects of electrolyte concentrations in the medium. An increase in osmotic pressure (produced by adding mannitol or NaCl) induced an immediate, but brief augmentation in cortisol release. Suppression of Na+ had no effect while its reintroduction in the medium led to stimulation of hormone release. By contrast, a sharp peak was obtained whenever Cl- concentration was dropped (by 50 mM fractions). These opposite effects of Na+ and Cl- when they vary independently of each other is interpreted with regard to osmoregulation and acid-base regulation. Raising K+ even to high levels (up to 20 mM) produced no change. The absence of Ca2+ had no obvious effect while its addition induced an immediate peak of cortisol release. In addition, external Ca2+ proved necessary for the action of ACTH to occur. These results establish that cortisol release in trout may be directly affected by changes in electrolyte concentrations in the extracellular space.