COLCHICINE. II. METABOLISM OF FROG SKELETAL MUSCLE

¹ Department of Pharmacology, Cornell University Medical College

Effects of colchicine on the frog sartorius muscle have been studied. A 10^-3 M concentration was without effect. Drug levels of 4 x 10^-3 M and 1.6 x 10^-2 M increased the force of contraction provided oxygen was liberally supplied. With the latter amount the increment in force was not maintained and muscles were unable to maintain tetanus. Both concentrations increased the oxygen consumption of muscle, without change in the respiratory quotient, and stimulated glycolysis under aerobic and anaerobic conditions. The effects on oxidation were inhibited by azide, malonate and fluoroacetate. Muscles manifesting potentiation of the contraction contained increased amounts of labile phosphate. An increase in colchicine concentration to 6.4 x 10^-2 M caused failure of the contraction, contracture, and reduced oxygen utilization, without significant effect on anaerobic glycolysis. The effects of colchicine resemble those of caffeine but the mechanisms of the actions are unknown. Previous suggestions that colchicine inhibits glycolysis or utilization of ATP were not confirmed.