Net transsarcolemmal Ca2+ shifts versus Ca/Ca exchange in guinea pig ventricular muscle

• Published in: Basic research in cardiology Vol. 85; no. 6; pp. 585 - 594
• Main Authors: WOLSKA, B. M, LEWARTOWSKI, B
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer 01-11-1990
• Subjects: Animals; Biological and medical sciences; Calcium - metabolism; Fundamental and applied biological sciences. Psychology; Guinea Pigs; Heart Ventricles; Homeostasis; Ion Exchange; Kinetics; Myocardium - metabolism; Sarcolemma - metabolism; Sodium - pharmacology; Vertebrates: cardiovascular system; Heart; Sarcolemma; Calcium; Pathophysiology; Animal; Heart ventricle; Ion exchange; Experimental study; Myocyte
• ISSN: 0300-8428; 1435-1803
• DOI: 10.1007/BF01907893

We investigated the net transsarcolemmal Ca2+ shifts and Ca/Ca exchange by means of 45Ca in isolated, perfused ventricles of guinea pig heart treated with vanadate to inhibit ATP-driven sarcolemmal Ca2+ pump. The heart was stimulated (at the rate of 60/min) and perfused with a solution containing 45Ca for 60 min. Thereafter stimulation was stopped and either perfusion with radioactive solution was continued or the solution was exchanged for a non-radioactive one. In the first case, tissue 45Ca content (equivalent to the exchangeable Ca2+ content) dropped from 1.960 +/- 0.120 mmol/kg of wet weight (w.w.) to 0.715 +/- 0.049 mmol/kg w.w. and stabilized at this level between 5th and 10th min. In the second case, decrease in 45Ca content continued and within 40 min attained 0.047 +/- 0.004 mmol/kg w.w., despite stabilizing of the total exchangeable Ca2+ content. Drop of 45Ca content in the rested heart perfused (until the end of experiments) with radioactive solution resulted from the net transsarcolemmal Ca2+ shift and it was strongly inhibited by removal of extracellular Na+. The continuing drop in 45Ca content in the heart perfused with non-radioactive solution while total Ca2+ content stabilized must have resulted from Ca/Ca exchange; it was stimulated by removal of extracellular Na+. These experiments separate two modes of 45Ca fluxes and suggest that a common route of these fluxes is the Na/Ca exchanger.