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

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.