고혈압백서 대동맥에서 Ca에 의한 수축에 미치는 Na/Ca교환기전의 영향 = Effects of Na/Ca Exchange on the Ca-induced Contration in Aorta of Spontaneously Hypertensive Rats

다국어 초록 (Multilingual Abstract)

We investigated the contraction by sodium-calcium(Na-Ca) exchanges in the aortic strips of spontaneously hypertensive rats(SHR) and Wistar-Kyoto (WKY) rats. Resting tension of aortic strips in SHR was decreased by the removal of extracellular Ca and those were recovered by the addition of Ca. However, resting tone of aortic strips in WKY was not changed by Ca removal or Ca addition. Ca-induced contraction after exposure to Ca-free solution was suppressed by verapamil 10^-6M to 90% or more.
In the presence of verapamil 10^-5M, phentolamine 10^-6M, caffeine 5mM and atropine 10^-6M, the reduction of extracellular sodium concentration([Na]o) from normal(158 mM) to 0 mM(replaced by choline chloride) caused the contraction(Ca entry by Na-Ca exchange). The amplitude of contraction was more greater in SHR than in WKY rats. In the presence of verapamil 10^-5M, phentolamine 10^-6M, caffeine 5mM and atropine 10^-6M, aortic strips were not contracted by Naand Ca-free solution, but was contracted by the addition of Ca. In the presence of verapamil 10^-5M and phentolamine 10^-6M and ouabain 10^-5M, Ca did not induce contraction after exposure to Ca-free Tyrode ' s solution, but in the presence of verapamil 10^-5M and phentolamine 10^-6M and monensin 10^-5M a sodium ionophore, Ca induced a little contraction in the aortic strips of SHR.
These observations suggest that Na-Ca exchange does not contribute the development of Ca-induced contraction after exposure to Ca-free Tyrode ' s Solution in the presence of normal extracellular Na concentration. However, Na/Ca exchange in vascular smooth muscle is increased in SHR and may be involved in the mechanism for hypertension in SHR.