Effects of corticosteroids on electrolyte metablism during osmoregulation in teleosts.

Abstract

The effects of injections of hydrocortisone, 9 α fluorohydrocortisone and d, l aldosterone on rates of loss of Na and K and on serum and muscle electrolyte concentrations were studied in euryhaline and stenohaline marine teleosts during immersion in fresh water for periods of 1–16 hours. Survival time was not affected by administration of adrenal steroids. Survival in fresh water was inversely correlated to the rates of Na loss. Administration of corticosteroids had no consistent effect on either Na or K loss or on the changes in plasma or muscle electrolyte content during immersion in fresh water. It is inferred from the data that euryhalinity depends on the ability to conserve Na, K and Cl in hypotonic water and that NaCl depletion, extracellular fluid contraction and hypovolemia are major factors in the failure of marine teleosts to survive in fresh water.