PROSTANOID-MEDIATED VASCULAR CONTRACTION IN NORMOTENSIVE AND HYPERTENSIVE RATS

We investigated the role of prostanoids in the constrictor effect of calcium ionophore A23187, endothelin-1 and vasopressin in rings of thoracic aorta obtained from normotensive rats and rats with aortic coarctation-induced hypertension. Isometric tension was measured in aortic rings bathed in buffer with and without indomethacin (10-mu-M), CGS13080 (10-mu-M) or SQ29548 (1-mu-M) to inhibit cyclooxygenase and thromboxane synthase and to block TxA2-PGH2 receptors, respectively. Increases in tension elicited by A23187 and vasopressin in aortic rings from hypertensive rats exceeded responses in rings from normotensive rats. A23187-induced contractions were virtually abolished by indomethacin and SQ29548, and slightly attenuated by CGS13080. These agents also attenuated the contractions elicited by endothelin but not by vasopressin. According to these data, a prostanoid(s) agonist for TxA2-PGH2 receptors contributes to the constrictor effect of A23187 in aortic rings of hypertensive rats, and of endothelin in aortic rings of normotensive and hypertensive rats. Moreover, the expression of prostanoid-mediated contractions as it pertains to the aortic response to A23187 is greatly increased in hypertensive rats.