The effect of calmodulin on the active calcium-ion transport and (Ca2+ + Mg2+)-dependent ATPase in microsomal fractions of smooth muscle compared with that in erythrocytes and cardiac muscle.
The Ca2+ uptake and the (Ca2+ + Mg2+)-dependent ATPase of the porcine coronary-artery smooth-muscle microsomal fraction ('microsomes') are only slightly stimulated by calmodulin. The Ca2+ uptake after 2 min in the absence of oxalate, corrected for the ATP-independent binding, increased by a factor of 1.44, whereas the (Ca2+ + Mg2+)-dependent ATPase is stimulated 1.39 times. These findings contrast with the effect observed in human erythrocyte 'inside-out' microsomes. In these vesicles calmodulin increases the Ca2+ uptake after 20 min in an oxalate-free medium and the (Ca2+ + Mg2+)-dependent ATPase respectively by a factor of 3.82 and 6.18. The magnitude of the calmodulin stimulation of the Ca2+ transport in coronary-artery microsomes is similar to that observed in heart microsomes.
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002147:Calmodulin / Q000494:pharmacology*; D004285:Dogs; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D006321:Heart / Q000187:drug effects; D006801:Humans; D008861:Microsomes / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D013552:Swine
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D000252:Calcium-Transporting ATPases; D002118:Calcium