Corticosteroid, catecholamine and glucose plasma levels in rabbits after repeated exposure to a novel environment or administration of (1-24) ACTH or insulin.

The responsiveness of the adrenal cortex and the sympatho-adrenal-medullary system to stress factors and administration of (1-24) ACTH and insulin was studied in adult rabbits. In comparison to untreated animals, exposure to a novel environment for 10 min followed by artery puncture on 6 consecutive days elicited a moderate increase of corticosteroid (C), norepinephrine (NE) and epinephrine (E) plasma levels. Intramuscular injection of 50 micrograms/kg body weight (1-24) ACTH increased C, NE and E plasma levels. Saline injection resulted in elevated NE levels; C, E and glucose remained unchanged. After injection of 1.0 IU/kg body weight insulin C levels were higher than those found after exposure to a novel environment for 10 min followed by artery puncture; similarly, NE and E increased. In accordance with results obtained in the rat or mouse the sympatho-adrenal-medullary system in the rabbit is stimulated by stress factors such as handling, artery puncture or injection of (1-24) ACTH or insulin. In contrast the adrenal cortex can be stimulated only to a certain extent by these manipulations. An increased activation of adrenal cortex cells occurs only after insulin, a maximum stimulation only after (1-24) ACTH administration.