흰쥐 자궁근에서 Na-제거 경축 및 Ba-경축에 관한 연구

Abstract

Mechanical responses to Ka---removal and Ba2+ ι'exposure were investigated in order to elucidate the -calcium sources for muscle contraction in the longi~ tudinal and circular muscles of rat myometrium. All experiments were performed in Tris-buffered Tyrode solution and preparations were usually taken from the uterus at oestrus stage The results obtained were as foil 。、:\' 5 1. Oxytocin CO.2mu mL and prostaglandin F ，α (0. 1μg/rol) induced regular spontaneous contractions -of the longitudinal and circular muscles of myometrium. The response of the circular muscle to PG F,a was more sensitive than that of the longitudinal muscle. 2. When most of sodium in Tyrode solution was replaced with Tris, mechanical contracture which has two components, tonic component 、:\' a s more prominent in the longitudinal muscle and phasic component in ,circular muscle , were produced. The contractures were relaxed immediately after readmission of sodium of normal and Sm1'vl concentrations. 3. Ba2+ C2mM) induced an initial phasic contrac· ture and a sustained tonic contracture. The tonic components were dependent upon the external calcium .eoncentra tions, but in higher concentrations of calcium (l2mM) were spontaneously relaxed. 4. f\.1n2+, in the concentration of O. GmM, \vhich is kno、.vn to be calcium-influx antagonist, reduced the magnitude of Ba2 '-contracture, mainly phasic component and in 2mM concentration abolished contrac ture, but not completely. The above results indicate that there are three components in mechanical contracture to Na~·-removal and Ba2c--exposure: the phasic and tonic components which are highly Ca'• dependent and the third small tonic component, which is independent of external Ca• . Most of the phasic and tonic responses seem to be due to increased calcium influx during membrane depolarization. And a N"a-Ca exchange mechanism is considered to contribute to transient phase of the response to Na-'--remoyal and Na:'-readmission