ENDOTHELIUM-INDEPENDENT PARTIAL AGONISTIC ACTIVITY OF VASOPRESSIN IN THE RAT COMMON CAROTID ARTERY

 

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It has been shown that vasopressin causes endothelium-dependent relaxations of the canine basilar artery, suggesting that_increased circulating concentrations of vasopressin can produce redistribution of the blood from the peripheral to the cerebral circulation (Katušić et al., 1984). The present experiments were done to examine effect of vasopressin on the rat peripheral arteries* The experiments were performed on rings (4 mm long) of aorta, common carotid and renal arteries* The arteries were placed in Krebs-Ringer-bicarbonate solution gassed with 95%O₂-5%co₂ gas mixture and kept at 37°c. In certain rings the endothelium was removed mechanically by gentle rubbing of the intimal surface. Isometric tension was continously recorded (IPM electronic).Vasopressin (10-11 to 3×10-8 M) caused concentration-dependent contraction being full agonist in aorta and renal artery, but partial agonist in common carotid artery. After removal of endothelium vasopressin-induced contractions were not significantlly afected in any of the tested arteries. Gyclooxygenase inhibitor indomethacin (10-5 M; contact time = 40 min) did not affect partial agonistic activity of vasopressin in common carotid artery. This results indicate that partial agonistic activity of vasopressin in common carotid artery is not related to increased production of "EDRF" or prostacyclin from endothelium. In addition, our findings are consistent with the hypothesis that vasopressin may contribute to redistribution of the blood flow from the peripheral to the cerbral circulation.

Z.S. Katušić, J.T. Shepherd and P.M. Vanhoutte. Circ. Res., 55: 575-579, 1984