Restoration of potassium-stimulated respiration of ‘glycerol-treated’ muscle

Abstract

Agents that produced contracture in skeletal muscle, such as caffeine or K-depolarization, also caused an increased rate of oxygen consumption. Both of these functions are calcium dependent. In this study the respiratory response to K-depolarization and to caffeine was monitored in lgycerol-treated and normal frog sartorius muscles. Although glycerol-treated muscle does not contract in response to K-depolarization, it does develope normal caffeine contractures. The respiratory response to both potassium and caffeine is greatly inhibited in glycerol-treated muscles. Pretreatment with dibutyryl cyclic AMP restored the respiratory response to normal levels in glycerol-treated muscle. Pretreatment with low levels of caffeine and resulted in a normal respiratory response to K-depolarization even though there was no tension development. Caffeine had no effect on adnyl cyclase activity even at concentrations that markedly stimulated oxygen uptake. The data suggest that potassium stimulation of oxygen uptake in glycerol-treated muscle is uncoupled by a defect in the formation of a cyclic nucleotid cofactor, rather than a defect in clacium influx.