THE INFLUENCE OF DRUGS WHICH STIMULATE SKELETAL MUSCLE AND OF THEIR ANTAGONISTS ON FLUX OF CALCIUM, POTASSIUM AND SODIUM IONS

¹ Experimental Pharmacology Division, Institute of Physiology, University of Glasgow, Glasgow, W. 2, Scotland

In the isolated frog sartorius muscle, depolarizing and contracture-producing drugs including suxamethonium, decamethonium, nicotine, ryanodine and neostigmine increased the uptake of calcium-47 and sodium-24 but depressed that of potassium-42. Suxamethonium, nicotine, ryanodine and neostigmine also increased the release of calcium-47 and potassium-42. Decamethonium increased the release of potassium-42. Edrophonium depressed the uptake of calcium-47 and potassium-42 and increased the release of calcium-47. Carbachol increased the release of potassium-42. Protoveratrine A and protoveratrine B depressed the uptake of calcium-47.

Tubocurarine and gallamine caused no change in the uptake of calcium-47, potassium-42 or sodium-24 or in the release of calcium-47 and potassium-42.

It is suggested that when depolarizing or contracture-producing drugs are used, calcium ions may become more mobile being dissociated from combination with a carrier or displaced from a binding site on the cell membrane. This may break down barriers which retain, against the concentration gradients, potassium ions within and sodium ions outside the cell.