RELEASE OF OXYTOCIN, VASOPRESSIN AND NEUROPHYSIN IN THE GOAT

Abstract

Neurophysin is considered to act as a carrier protein for oxytocin and arginine vasopressin (AVP) in the neurohypophysis, and recent evidence has suggested that neurophysin is released into the blood together with the neurohypophysial hormones in response to various stimuli (Cheng & Friesen, 1970). Neurophysin, extracted from bovine pituitary posterior lobes, consists of two major components designated neurophysin I and II (Hollenberg & Hope, 1968) both of which bind oxytocin and AVP in vitro, although neurophysin II appears to be located specifically in neurosecretory granules containing AVP (Dean, Hope & Kazie, 1968). We now report results relating to the release of neurophysin, oxytocin and vasopressin into the blood in response to hand-milking, mating and haemorrhage in the goat. Consecutive serial blood samples (approximately 25 ml each) were taken from an indwelling jugular cannula during hand-milking in one goat and during mating in four oestrous female goats (McNeilly & Folley, 1970).