Hydralazine Prevents Changes in the Contractile Response of Aortic but Not Portal Vein Strips in Hypertensive Rats

Abstract

Previous studies showed that aortic strips from rats with either spontaneous (SHR) or DOCA/salt-induced hypertension developed less stress (force/area) in response to noradrenaline (NA) when compared to aortic strips from normotensive rats. Portal vein strips from SHR, but not from DOCA/salt hypertensive rats, developed greater force to NA compared to strips from control rats. We have investigated whether these changes are prevented by hydralazine. Hydralazine was added to the drinking solution (1% NACl) of one group of rats from the first day of treatment with DOCA. In the second group, hydralazine was added to the drinking water of 13-week-old SHR. After 3 weeks of treatment with hydralazine, cumulative dose-response relationships to NA were studied using aortic and portal vein strips from hydralazine-treated and control rats. Hydralazine prevented the increase of arterial pressure and the decrease of stress developed to NA by the aortic strips from both SHR and DOCA/salt rats. It did not prevent the increase of force developed to NA by the portal vein strips from SHR. Thus, reduced contractile response of the aortic strips from hypertensive rats seems to be the result of a high pressure, since both the rise in blood pressure and reduced aortic response are prevented by hydralazine. Increased contractile response of the portal vein strips from SHR appears to be independent of blood pressure.