[Noradrenaline regulation of the energy of heat production and ATP utilization during normal single muscle contraction and in hyperoxia].

The effect of noradrenalin (NA, 0.008 microgram/ml) on the rate of heat release (V) during a single isometric contraction of an isolated diaphragm was investigated in rats kept in air and 99% oxygen for 3 hours. The effect was measured by the electrothermometric method in the presence and in the absence of ATP (0.01 mg/ml) in the incubation solution. Hyperoxia doubled V of muscle contraction. The calorigenic effect of NA was not detected in the norm and was very distinct during hyperoxia so that VNA = 0.14X XVinit + 10.88. ATP addition increased V both in the normal and hyperoxic state. However, the increase of the initial V level was 5.3-fold in the hyporexoc state and 1.5-fold in the norm. It is concluded that hyperoxia disturbs energy metabolism of muscle contraction through NA-dependent acceleration of ATP-lytic processes and increase of energy expenditures of heat formation in the course of muscle contraction.