Differential effects of D 600 on contractile response of aorta and portal vein from spontaneously hypertensive rats.

To examine if Ca handling by vascular smooth muscles is altered in hypertension, the in vitro effect of D 600 was determined on noradrenaline-induced contractions of aortic and portal vein strips from spontaneously hypertensive rats (SHR) and Wistar Kyoto normotensive rats (WKY). In low (0.2 and 0.4 mM) Ca solutions, D 600 reduced the response to noradrenaline to a greater extent in aortic strips from SHR than in strips from WKY. In contrast, D 600 had less effect on the response to noradrenaline in portal vein strips from SHR than in strips from WKY in both normal and low Ca. Thus, portal veins from SHR are less dependent on external Ca compared to portal veins from WKY whereas aortae from SHR are more dependent on external Ca compared to aortae from WKY.