Depressing effects of calcium antagonists on oxygen consumption in isolated skeletal muscle during potassium depolarization

Abstract

The effects of two Ca2+-antagonizing drugs, dantrolene sodium (DAN) and TMB-8, on subcontracture, K+-induced increased oxygen consumption were studied in isolated frog sartorius muscles. Incubation in Ringer's solution +18 mM KCl caused a marked increase in averaged resting oxygen uptake (52.8 ± 4.1 to 278.2 ± 20.0 mm3∙g−1∙h−1). Incubation in Ringer 's +18 mM KCl containing either 0.116 mM TMB-8 or 0.035 mM DAN resulted in a significant reduction in the averaged metabolic response (264.4 ± 30.8 (control) vs. 142.3 ± 19.0 (TMB-8) vs. 72.2 ± 3.4 (DAN)). The results suggest that the enhanced metabolic rate observed upon elevating extracellular [K+] to just below contracture levels is due to increased intracellular Ca2+ release.