AGE-DEPENDENT MODIFICATIONS OF THE ROLE OF PROSTANOIDS IN CARDIAC PREPARATIONS FROM NORMOTENSIVE AND HYPERTENSIVE RATS

The cardiac response to field stimulation of adrenergic nerve terminals in isolated atrial preparations from adult (6-month-old) normotensive Wistar Kyoto (WKY) and spontaneously hypertensive (SH) rats was enhanced in comparison to that observed in the atrial tissue of young (2-month-old) animals of both strains; the increase in the sympathetic response was significantly higher in preparations from SHR than in those from age-matched WKY rats. The sensitivity of cardiac adrenergic neurotransmission to the prejunctional inhibitory effects exerted by exogenously administered prostaglandin E2 (0.1 nM-1 μM) and iloprost (0.1-10 μM) did not show any strain-dependent difference in preparations from both young and adult rats. Moreover, acetylsalicylic acid (500 μM) induced a similar degree of potentiation of the response to sympathetic stimulation in atrial tissues of young WKY and SH animals; however, the effect of the cyclo-oxygenase inhibitor was completely missing in preparations from adult rats of both strains. Finally, arachidonic acid (10 μM) inhibited the adrenergic response to a greater extent in preparations from young and adult SH rats than in those from age-matched normotensive rats. The results of the study indicate that, at least in cardiac preparations, changes in the modulatory role of endogenous prostaglandins occur as age-dependent processes and, therefore, may not be indicative of possible differences in the role of prostaglandins between hypertensive and normotensive animals. The possible significance of the dissimilar response to arachidonic acid, detected as the only difference between preparations from SH and WKY rats, is discussed. © 1993 The Italian Pharmacological Society.