The aerobic metabolism of porcine carotid artery and its relationship to isometric force. Energy cost of isometric contraction.

1. The O2 consumption and aerobic lactate production of porcine carotid artery have been studied in relation to active isometric tension maintenance in order to estimate the tension cost, i.e., ATP hydrolysis rate per unit force maintained. 2. The relationship between total metabolism and isometric force was measured at several muscle lengths in order to distinguish tension-dependent and -independent components of ATP utilization. 3. At the maximum isometric tension observed, 2 kg wt/wt/cm2, 1.3 mumole ATP/M in per gram wet weight out of a total metabolism of 2 mumole/min is tension de pardent. 4. The absolute levels of force, O2 consumption, lactate production and the ratio of oxidative to glycolytic metabolism varied considerably with the stimulant; however, the tension-dependent ATP utilization was invariant with respect to the mode of stimulation.