STUDIES ON THE DIRECT VASODILATOR EFFECT OF HYDRALAZINE IN THE ISOLATED RABBIT RENAL-ARTERY

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  • 1 January 1981
    • journal article
    • research article
    • Vol. 216  (2) , 390-394
Abstract
In contrast to other large arteries commonly used in organ bath studies, the rabbit renal artery is highly sensitive to the vasodilator action of hydralazine. Helical strips contracted by 10-7 M norepinephrine [NE] started to relax at a threshold concentration of 3.9 .times. 10-8 M hydralazine (IC10 [concentration which causes 10% inhibition]). The IC50 [median inhibitory concentration] was 1.4 .times. 10-7 M and at 3 .times. 10-6 M hydralazine, the preparations had relaxed almost completely. The development of relaxation was slow, lasting up to 1 h. Dose-response curves to NE in the presence of hydralazine were shifted to the right in parallel fashion at an only slight reduction of the maximum response. Contractions of rabbit renal artery strips induced by 45 mM KCl, or by 10-7 M NE superimposed on the KCl-induced tone, were almost unresponsive to hydralazine. Prolonged incubation of the arterial strips with 10-5 M ouabain abolished the response to hydralazine probably due to a ouabain-induced depolarization. Indomethacin, an inhibitor of tissue prostaglandin [PG] synthesis, and sulpiride, an antagonist to dopamine did not interfere with the vasodilator action of hydralazine. The relaxant effect of hydralazine may not be mediated by locally formed PG and that it is not dopaminergic in nature. Hydralazine is a potent direct vasodilator with a predominant action on pharmacomechanical coupling but little effect of electromechanical coupling.