Na-Ca exchange in a smooth muscle plasma membrane-enriched fraction

Na-Ca exchange in the plasma membrane-enriched fraction N1 isolated from rat myometrium has been demonstrated as Ca gain or loss depending on the direction of the [Na+] gradient [Grover et al., Am. J. Physiol. 240 (Cell Physiol. 9): C175-C182, 1981]. In this study, the [Na+]gradient-dependent Ca uptake by this membrane fraction was demonstrated to occur optimally at pH 6.67; and 7.0 +/- 2.2 microMs Ca2+ was required for the half-maximal uptake. …