Secretion of corticotropin releasing factor (CRF) and vasopressin (AVP) into the hypophysial portal blood of conscious, unrestrained rams.

The secretion of Corticotropin-Releasing Factor (CRF) and Arginine Vasopressin (AVP) into sheep hypothalamo-hypophysial portal blood was investigated in conscious, unrestrained castrated rams. One to two hours after the onset of the collection, peripheral ACTH and cortisol levels were within the basal range in all the animals and portal CRF and AVP concentrations were low ranging between 5 and 90 pg/ml. After acute hemorrhage, a sharp increase in portal CRF and AVP was observed, inducing a sustained elevation of peripheral ACTH and cortisol. These data show that measurements of CRF and AVP in the portal blood of conscious sheep provide a good methodology to study the regulation of basal and stress-induced ACTH secretion.