The stress response in the abundance of circulating leucocytes in the killifish, <i>Fundulus heteroclitus</i> III. The role of the adrenal cortex and a concluding discussion of the leucocyte‐stress syndrome

Abstract

Abstract The response of intact Fundulus heteroclitus to intraperitoneal injections of ACTH at two hours post‐injection depends on the dose: leucopenia at low doses, leucocytosis at high doses. The two hour response to cortisol, at 5 μg/g, depends on the condition of the fish: leucocytosis in sexually mature or hypophysectomized fish, leucopenia in sexually regressed intact fish. At a physiological dose (0.025 μg/g) cortisol elicits a time sequence response in hypophysectomized recipients that is, initially, the reverse of that observed after coldshock: three minute leucocytosis, 15 minute leucopenia, and return to normal at 45 minutes. Leucocytosis emerges at two hours. Pretreatment with Metopirone for five to six days in the aquarium water is not well tolerated. Such treatment effectively blocks all phases of the cold‐shock response. Pretreatment for two days was tolerated and, in such fish, injection of epinephrine (1 μg/g) elicits both three minute and 30–60 minute leucopenia, but the leucocytic phases are blocked. A tentative interpretation of the cold‐shock sequence is proposed on the assumption that catecholamines (presumably epinephrine) are leucopenic and that cortisol is leucocytic.