In VitroAdrenocorticotropin/β-Endorphin-Releasing Activity of Vasopressin Analogs Is Related neither to Pressor nor to Antidiuretic Activity*

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Abstract
The ability of vasopressin and related analogs to induce ACTH, .beta.-endorphin and .beta.-lipotropin release was studied in vitro using incubated rat anterior pituitary quarters or a perifused rat isolated anterior pituitary cell column. Vasopressin and its analogs exhibited corticotropin-releasing factor (CRF)-like activity in a rank order which was different from those for vasopressor or antidiuretic activity. Two dissimilar antagonists with antivasopressor activity showed different effects: one possessed CRF-like activity itself, the other blocked the CRF-like activity of vasopressin. Another antagonist with antipressor and also antiantidiuretic activity had no effect when given alone and also didn''t block the CRF-like activity of vasopressin. Some analogs were also tested for their effects on cAMP accumulation. Analogs, which possessed CRF-like activity or blocked CRF-like activity of vasopressin, stimulated cAMP accumulation in anterior pituitary quarters, respectively. Apparently the structural requirements of the CRF-like activity of vasopressin differ from those of the pressor and antidiuretic activity. The pituitary receptors responsible for CRF-like activity of vasopressin may represent a separate category of vasopressin receptors which may be linked to an adenylate cyclase.

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