Cellular calcium turnover in the perfused rat heart: modulation by caffeine and procaine.
Pool A is a rapidly exchangeable cellular pool of Ca++ whose release is triggered by a mechanism involving extracellular Ca++ (Hunter et al., 1981). We have now found that pool A is rapidly released from the perfused rat heart when 10 mm caffeine is added to the perfusate. Pool A release by caffeine was demonstrated during a Ca++ free perfusion. When the perfusate contained 2.5 mm Ca++, caffeine induced an immediate contractile failure. The steady state level of pool A (normally 69 +/- 10 nmol Ca++/g wet wt heart) was also decreased by 60%. Pool A was similarly depleted in hearts perfused with medium containing 0.2 mm Ca++. Procaine (5 mm) inhibited by 50% the release of pool A triggered by caffeine and inhibited by 86% the release triggered by extracellular Ca++. The inhibition of Ca++-induced release of pool A by procaine was partially relieved by externally stimulating the hearts. External stimulation also decreased the inhibition by procaine of Ca++ uptake by pool A from 83% to 28%. These results are further evidence that pool A is located in the sarcoplasmic reticulum and that release of pool A to the myofibriles is triggered by excitation-dependent Ca++ influx.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D005260:Female; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010477:Perfusion; D011343:Procaine / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012519:Sarcoplasmic Reticulum / Q000187:drug effects
D000001:Calcimycin; D002110:Caffeine; D011343:Procaine; D002118:Calcium