A STATIONARY MANOMETRIC RESPIROMETER FOR ISOLATED RAT DIAPHRAGM ALLOWING SIMULTANEOUS DIRECT REGISTRATION OF MECHANICAL ACTIVITY. OBSERVATIONS WITH SODIUM AZIDE AND DINITROPHENOL

¹ College of Pharmacy, Drake University, Des Moines, Iowa
² Department of Pharmacology, University of Michigan, Ann Arbor

1. A stationary respirometer for studying activity and resting metabolism of isolated mammalian skeletal muscle is described. It is a constant volume glass vessel wherein oxygen consumption is measured manometrically.

2. 2,4 Dinitrophenol (10^-6 M) caused about one-third increase in resting respirations without contracture (direct kymographic recording). At 10^-5 M, respirations was more than doubled arid contracture induced. The onset of contracture was delayed about thirty minutes, but there was no significant difference its the respiratory rate before and after onset of contracture.

3. Sodium azide (10^-4 M) caused a small but significant increase in resting respiration, also without inducing contracture. At 10^-3 M, there was a greater increase its respiration, but such concentrations rapidly led to a contracture within a few minutes.

4. Maximal isometric twitches at 200 per minute for 30 minutes increased the mean Q_O2 of controls from 4.22 to 6.88. At the sub-contracture concentration of dinitrophenol, the muscles contracted normally and the increased oxygen uptake due to activity did not differ significantly from control values. Similar results were obtained at sub-contracture concentrations of sodium azide.