Antidiuretic Hormone in Cerebrospinal Fluid During Endogenous and Exogenous Changes in Its Blood Level

Abstract

Antidiuretic activity in blood plasma, sampled from conscious and pentobarbital- anesthetized dogs and rabbits, and in cisternal CSF, obtained under anesthesia, was assayed in water-loaded ethanol-anesthetized rats. No activity was detected in peripheral plasma from conscious or anesthetized dogs and rabbits in the resting state; only slight activity (5–10 μ/ml) was found in occasional samples of CSF, withdrawn from animals at ½ or 2½ hr after induction of anesthesia. Thirty min after severe hemorrhage, the mean antidiuretic activity in arterial plasma was equivalent to 415 μU/ml AVP in the dogs and 79 μU/ml in the rabbits. CSF was 47 μU/ml (dogs) and 17 μU/ml (rabbits). Both CSF and plasma antidiuretic activity was completely inactivated with human pregnancy plasma or with vasopressin antiserum, and therefore is almost certainly due to endogenous vasopressin. Antidiuretic activity could not be detected in the CSF of 3 dogs after intravenous infusion of arginine vasopressin with a rise of plasma antidiuretic levels to above 100 μU/ml for 2 hr. The results indicate the presence of a blood-CSF barrier to vasopressin, and the stimulus of bleeding causes a release of ADH directly into the CSF as well as into the blood stream. (Endocrinology83: 246, 1968)