The effect of metabolic inhibitors on the electrical and mechanical activity of the smooth muscle of the guinea‐pig's taenia coli

The rate of oxygen consumption by smooth muscle is normally proportional, over a wide range, to the tension produced in isometric conditions (Biilbring, 1953). Under the influence of 2:4-dinitrophenol (DNP) in concentrations from 3 x 10-6 to 3 x 10-4M the oxygen consumption is increased (Born & Biulbring, 1955). In the lower part of this range of DNP concentrations there is also some slight, though not proportional, increase in tension and spontaneous activity. But with higher concentrations of DNP the oxygen consumption may rise to more than twice the normal rate, while the muscle tension remains unchanged or declines. At the same time the adenosine triphosphate (ATP) content in the muscle remains unchanged until, during exposure to high DNP concentrations, it decreases in parallel with the declining muscle tension. Born (1956) found a close parallelism between smooth muscle tension and creatine phosphate content in the absence of glucose or of oxygen. In normal conditions any change in tension which the smooth muscle of the taenia coli produces is associated with a change in membrane potential, in the frequency of spike discharge (Biilbring, 1955) and also with a change in spike configuration (Biilbring, 1956, 1957). We have now studied the effect of metabolic inhibitors on the electrical activity in relation to muscle tension. We have found a dissociation of the electrical from the mechanical manifestations which may in part account for the disproportion between the rate of metabolism and the mechanical activity.