High-energy phosphate compounds in human slow-twitch and fast-twitch muscle fibres

Abstract

A method was developed for separating slow- and fast-twitch fibers from the same muscle for analysis of high-energy phosphate compounds by an enzymatic fluorometric technique. Since the ATP and creatine phosphate concentrations in single muscle fibers are at pmol levels, enzymatic cycling is necessary to measure the NADPH formed in the reaction. The precision of the method is 3.3% for ATP and 2.0% for creatine phosphate. Variations in the levels of high-energy phosphate compounds were no greater between fibers of the same type than regionally within a single fiber. When slow- and fast-twitch fibers were compared, there were no significant differences in the high-energy phosphate concentrations, except that in women there was significantly more creatine phosphate in slow-twitch than in fast-twitch fibers.