Caffeine does not contract skinned uterine fibers with a functional Ca store.
Chemically skinned fibers were prepared from pregnant rat myometrium. In the presence of a low EGTA concentration (0.1 mM), caffeine (0.1-50 mM) produced no contraction whereas both inositol-1,4,5,-triphosphate and the ionophore A23187 evoked contractile responses insensitive to cyanide and azide. Furthermore, caffeine antagonized the maximal contractions induced by pCa = 5 (in the presence of 4 mM EGTA). It is concluded that caffeine inhibits some mechanism of the contraction in rat myometrium and thus that caffeine is not a good tool for the study of intracellular Ca stores in this smooth muscle.
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D004533:Egtazic Acid / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D007293:Inosine Triphosphate / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009215:Myometrium / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D014590:Uterine Contraction / Q000187:drug effects*
D007293:Inosine Triphosphate; D000001:Calcimycin; D002110:Caffeine; D004533:Egtazic Acid; D002118:Calcium