Separation of aerobic glycolysis from oxidative metabolism and contractility in rat anococcygeus muscle

Abstract

The relationship of aerobic glycolysis (JLac) and O2 utilization (JO2) to contractility and the activity of the Na+-K+ pump was investigated in rat anococcygeus smooth muscle. Removal of extracellular potassium concentration ([K+]o) caused an initial increase followed by a decrease in JLac below the resting rate. Restoration of [K+]o caused JLac to increase, and this response, but not the initial one observed in zero [K+]o, was prevented by ouabain. These changes in JLac were not related to contractility, since a similar response was observed in both phentolamine-treated and chemically denervated muscles that exhibited minimal force and no significant changes in JO2. Tension development of innervated muscles incubated in K+-free medium was related to changes in JO2. A logarithmic relationship between JLac and [K+]o suggested that changes in JLac resulted from effects on glucose transport or utilization secondary to changes in the membrane potential. In stimulated muscles JLac and JO2 were both positively correlated with isometric force and were not affected by ouabain. Separation of JLac from JO2 and force production under some conditions supports the hypothesis that a functional compartmentalization of metabolic pathways exists in anococcygeus muscle.