Properties of rat anterior pituitary vasopressin receptors: relation to adenylate cyclase and the effect of corticotropin-releasing factor.

Publisher Website
Google Scholar
Abstract
Crude plasma membrane fractions were prepared from female Wistar rat anterior pituitaries. These fractions contained a single population of specific 3H-labeled [8-lysine]vasopressin ([3H]vasopressin) binding sites with a (Kd) of 8 .+-. 2 .times. 10-9 M and maximal binding capacity of 244 .+-. 45 fmol/mg of protein. The Kd values for a series of vasopressin structural analogs with selective vasopressor of antidiuretic activities were determined together with the corresponding corticotropin-releasing activities (isolated perfused pituitary cells were used). A good correspondence was found between the 2 sets of values, suggesting that the detected vasopressin binding sites are the receptors involved in vasopressin-induced corticotropin release. The order of potency of these analogs for the binding to hypophyseal receptors was similar to that found for the binding to the receptors involved in the vasopressor response. Corticotropin-releasing factor [CRF] and angiotensin did not affect vasopressin binding to pituitary membranes. Median eminence extracts inhibited [3H]vasopressin binding with an efficiency very close to that expected from their vasopressin content. CRF activated, and angiotensin inhibited, the adenylate cyclase activity of pituitary membranes. Under the same experimental conditions, vasopressin did not influence adenylate cyclase activity nor did it affect the CRF-induced activation. Vasopressin is apparently 1 component of the multifactorial regulation of corticotropin release and it acts through a cAMP-independent pathway. The potentiation by vasopressin of CRF-induced cAMP accumulation in intact cells very likely proceeds through indirect mechanisms, which are not expressed in broken cell preparations.