Constrictory activity of three new arginine-vasopressin (AVP) analogues (Ala-AVP, Ser-Ala-AVP, Thr-Ser-Ala-AVP) towards isolated rat tail artery as related to AVP alone.

The constrictory activity of vasopressin and its three novel analogues extended by 1-3 amino acids in accordance with the sequence of the bovine arginine-vasopressin neurophysin II precursor has been studied on isolated rat tail artery preparation. The analogues showed lower constrictory potency than AVP, but these agents strongly interacted with AVP. The net effect of interactions appeared complex and dependent on the nature and concentrations of the interacting agents. Basing on recent findings (Land et al. 1982) concerning the sequence of the bovine arginine-vasopressin neurophysin II precursor, Lammek et al. (1987) synthesized vasopressin analogues with primary structures derived from this precursor. Three such analogues, Ala-AVP, Ser-Ala-AVP, and Thr-Ser-Ala-AVP, showed pressor activity (147, 109, and 86 international units/mumol respectively) and antidiuretic activity (52, 130, and 48 international units/mumol, respectively) after intravenous administration to rats (Lammek et al. 1987). Having in view the possible clinical applications of vasopressin analogues and hormonogens in the treatment of bleeding disorders we were interested in the direct effect of the agents on isolated blood vessels. As the analogues considered may theoretically appear in a living system and interact with the native AVP, such interaction on the isolated rat tail artery preparation was analysed.