Characterization of immunoreactive AVP in the ovine hypothalamo-pituitary axis

The aims of these studies were to determine the precise molecular nature of immunoreactive (IR-) vasopressin (AVP) in the ovine hypothalamo-pituitary axis and to examine a possible role for glucocorticoids in regulating both AVP processing and levels in this axis. The IR-AVP in extracts of paraventricular nucleus, median eminence, portal blood, and anterior and neurointermediate pituitary elutes as a single peak on two distinct HPLC solvent systems, suggesting that AVP is processed identically in these tissues. Identical profiles were also found in extracts from pituitaries and sheep subjected to chronic (10 days) glucocorticoid treatment, or hypothalamo-pituitary disconnection. The latter findings confirm that in sheep, like the rat, AVP is synthesized and processed in the anterior pituitary and is not sequestered from extrapituitary sources.