The role of sarcolemma and mitochondria in regulating Ca2+ movements in human myometrium.
A subcellular fraction enriched in sarcolemma was isolated by differential and sucrose gradient centrifugation from human myometrium. The Ca2+ binding characteristics of this fraction were compared to that of mitochondria and microsomes that were isolated simultaneously. 1. Oxalate increased ATP-dependent Ca2+ uptake by the sarcolemmal but not the mitochondrial fraction, while azide inhibited mitochondrial but not sarcolemmanl Ca2+ transport. 2. The amount of Ca2+ bound in 10 min by these two fractions from a 0.3 muM free Ca2+ solution was similar, but the rate of Ca2+ uptake at 1 muM Ca2+ was greater for the mitochondrial than the sarcolemmal. fraction. The properties of Ca2+ binding by the microsomal fraction were intermediate between these two fractions. 3. The results suggest that mitochondria have a greater potential for lowering intracellular Ca2+ activity in human myometrium than do sarcolemma or sarcoplasmic reticulum.
D000328:Adult; D001386:Azides / Q000494:pharmacology; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D005260:Female; D006801:Humans; D008861:Microsomes / Q000378:metabolism; D008931:Mitochondria, Muscle / Q000378:metabolism*; D009215:Myometrium / Q000378:metabolism* / Q000648:ultrastructure; D010070:Oxalates / Q000494:pharmacology; D011485:Protein Binding; D012508:Sarcolemma / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D014599:Uterus / Q000378:metabolism*
D001386:Azides; D010070:Oxalates; D002118:Calcium