ACTH, CORTISOL AND GLUCOSE RESPONSES AFTER ADMINISTRATION OF VASOPRESSIN IN CATTLE AND SHEEP

The present study compared the effects of vasopressin on plasma concen trations of corticotropin, cortisol and glucose in cattle and sheep. A fter intravenous injection of 1, 0.1 and 0.01 mu g vasopressin per kg body weight, the plasma vasopressin concentration increased proportion ally to the injected dose, and this increase was similar in cattle and sheep. Doses of 1 and 0.1 mu g per kg body weight of vasopressin trig gered significant responses of corticotropin, cortisol and glucose in cattle and sheep. The corticotropin response to both doses was signifi cantly greater in sheep, whereas the glucose response was greater in c attle. The cortisol response did not differ between species. The lowes t dose of vasopressin (0.01 mu g per kg body weight) still induced a s ignificant cortisol response without a substantial effect on plasma co rticotropin, suggesting that a direct action of vasopressin on the adr enals may contribute to the observed cortisol response. The results de monstrate that vasopressin increases plasma levels of corticotropin, c ortisol and glucose in cattle, as it does in sheep, but the intensitie s of the corticotropin and glucose responses to vasopressin differ bet ween cattle and sheep. The reasons for these differences remain to be clarified.