title: High affinity Ca-binding to smooth muscle plasma membrane: inhibition by cations.
abstract: The effects of Mg2+, Na+ and K+ on the pH-dependent high affinity passive Ca-binding to sarcolemmal enriched membrane fractions from the smooth muscles of rat myometrium and gastric fundus were examined at 1 uM Ca2+-concentration. For the myometrial plasma membranes, these ions inhibited the passive Ca-binding with the following IC50 values: Mg2+: 1.75 mM; Na+: 19 mM; K+: 233 mM. Similarly, for the gastric fundus membranes, the IC50 values were Mg2+:1.6 mM, Na+:46 mM and K+:67 mM.
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D005748:Gastric Fundus / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009130:Muscle, Smooth / Q000378:metabolism*; D009215:Myometrium / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D012964:Sodium / Q000494:pharmacology
chemical_list: D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium