Calcium in the in situ mitochondria of rested and stimulated myocardium.
Calcium is believed to provide feedback between myocardial energy consumption and production. Calcium content was proved to increase in mitochondria (MT) isolated from (1) stimulated hearts, and (2) hearts of increased contractility. In this work we compared Ca2+ content in the intact MT of skinned strips excised at 0 degrees C from previously stimulated or rested guinea-pig ventricles equilibrated with 45Ca and in single rested or stimulated myocytes. In both preparations Ca2+ was released from MT by means of CCCP (carbonyl cyanide m-chlorophenyl-hydrazone; 100 microM). CCCP released 1.58 +/- 0.55 nmol Ca2+/mg of MT protein from the strips of rested hearts and 3.86 +/- 1.12 nmol Ca2+/mg of MT protein from the stimulated muscles. Stimulated myocytes responded to the close micro-injection of CCCP with transient contracture which was not inhibited by caffeine (10 mM) or ryanodine (0.1 microM, 45 min), although the time-course of the contracture was changed. Contracture could not be initiated in rested cells. It is suggested that in rested myocytes MT contain much less Ca2+ than in stimulated ones.
Wolska
B M
BM
Department of Clinical Physiology, Medical Center of Postgraduate Education, Warsaw, Poland.
Lewartowski
B
B
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000008:administration & dosage / Q000494:pharmacology; D004558:Electric Stimulation; D006168:Guinea Pigs; D008845:Microinjections; D008929:Mitochondria, Heart / Q000378:metabolism*; D009200:Myocardial Contraction / Q000187:drug effects; D012433:Ryanodine / Q000494:pharmacology
D012433:Ryanodine; D002110:Caffeine; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D002118:Calcium