A Na～+-Ca～(2+) Exchange Process In Isolated Thoracic Aortic Rings From WKY And RH Rats

Object: In the present study, the effects of reducing Na+ gradient (reducing external Na+ or increasing internal Na+) on evoked tension in thoracic aortic rings of two-kidney, one-clip model of hypertension were observed. So we can study the activities of Na+-Ca2+ exchanger in aortic rings of RH rats.Method: Using isolated vascular method to study the difference of thoracic aortic rings' tension between RH and WKY rats when change Na+ gradient.Result: In isolated thoracic aortic rings, the contraction, induced by Noradrenaline (NE), was increased in RH rats (887±127mg/mg.ww) as compared with WKY rats (478?01 mg/mg.ww). When reducing external Na+ the contraction of NE was increased in thoracic aortic rings of both WKY and RH rats, but the degree of this increase was much lower in RH (8.3%) compared with WKY rats(18.1%), and the difference was statistically significant; When increasing internal Na+, the contraction of NE was increased in both WKY and RH rats, but the degree of this increase was much lower in RH (6.9%) compared with WKY rats(17.1%), and the difference was alsostatistically significant.Conclusion: These results suggested that: 1. augmented internal Ca2+ could induce the amplified NE-induced contractions in thoracic aortic rings under reduced Na+ gradient conditions; 2. the activity of Na+-Ca2+ exchanger of RH rats was different from that of WKY rats, so Na+-Ca2+ exchange process was likely to regulate internal calcium and vascular smooth muscle contractility and was perhaps involved in the development and maintenance of renal hypertension.