Efflux of 45Ca from isolated smooth muscle cells of guinea-pig taenia caeci.
Single smooth muscle cells were isolated from guinea-pig taenia caeci by digestion with collagenase. The 45Ca desaturation curve from isolated cells, which were previously washed with Ca2+-free solution containing EGTA in Ca2+-free modified Locke solution, consisted of three components (half-time: 1.0, 3.8 and 12.4 min). The 45Ca efflux from isolated cells in the third component was significantly increased by caffeine. This increase was suppressed by procaine, but was not affected by La3+. These results suggest that, in guinea-pig taenia caeci, there are at least four Ca2+ compartments: superficial low and high affinity bound Ca2+ and cellular low and high affinity bound Ca2+. Caffeine releases Ca2+ from the cellular high affinity binding sites.
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D002432:Cecum / Q000187:drug effects / Q000378:metabolism; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007700:Kinetics; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*
D002132:Calcium Radioisotopes; D002110:Caffeine; D002118:Calcium