6533b7dafe1ef96bd126eaa9

RESEARCH PRODUCT

Der Einflu� von Monojodessigs�ure auf das Aktionspotential des Rattenzwerchfells

subject

description

1. The action of iodoacetic acid (IA) was studied on the isolated rat diaphragm at 20–22° C. Membrane and action potentials were led off with intracellular microelectrodes. 2. IA causes a contracture which is complete in 4 hours. As long as t he contracture develops, the membrane potential remains constant. A contracture identical with that seen in a normal preparation can be produced by IA in the presence of isotonic K2SO4. 3. The amplitude of the action potential is only slightly reduced during the first two hours after addition of IA. The duration of the action potential is significantly increased. Finally, action potentials with a plateau are obtained which resemble those of normal ventricular muscle. 4. The prolongation of the action potential caused by IA cannot be eliminated by the addition of pyruvate. 5. The diaphragm suspended in Tyrode's solution loses potassium and gains an equivalent amount of sodium. After addition of IA the loss of potassium is significantly increased, but the uptake of sodium is not altered. There was a small increase of the fibre water. 6. The overshoot is linearly related to the logarithm of the sodium concentration in the external fluid. The slope for a tenfold change in sodium concentration was 59.6 mV. 60–90 minutes after IA, neither the rate of rise of the action potential nor the relation between sodium concentration and overshoot is affected. 7. It is concluded that IA prolongs the action potential by an effect on membrane permeability during activity rather than by changing ionic gradients between intra- and extracellular space.