IODOACETIC ACID AND ANAEROBIC MUSCULAR CONTRACTION

Abstract

The first reactions taking place in contraction of isolated muscles of iodoacetate poisoned frogs are the conversion of phosphocreatine to hexosemonophosphate and some phosphocreatine hydrolysis. Contracture begins when practically all the phosphocreatine has broken down, and adenosine triphosphate breakdown begins at this point. In complete rigor, hexosediphosphate is formed by conversion of the monophosphate into diphosphate. Inorganic phosphate is utilized as readily as adenosine triphosphate for this reaction. No evidence was found for the presence of triosephosphate, although it is stated by Meyerhof and Lohmann that iodoacetic acid does not affect the formation of this substance from hexosediphosphate in extracts. The formation of hexosemonophosphate is a process independent of the formation of lactic acid, rather than an intermediate step in the formation of the latter substance. Hexosemonophosphate formation directly from phosphocreatine and diphosphate formation from inorganic P have not been found in muscle extracts. Caution is necessary in transferring findings in muscle extract to contraction in the intact muscle.