High-energy phosphate compounds in slow-twitch and fast-twitch muscle fibres: Changes during exercise in some neuromuscular diseases

Abstract

Concentrations of the high-energy phosphates, ATP and creatine phosphate, were investigated in slow-twitch (ST) and fast-twitch (FT) muscle fibres of patients with myotonia congenita (n = 6), dystrophia myotonica (n = 5), myopathia ocularis (n = 2) and hyperornithinemia with gyrate atrophy (HOGA) (n = 3) and compared with those of normal subjects (n = 4). At rest, the patients with HOGA had lower values of ATP in ST muscle fibres than the controls ( P < 0.05). They also had lower values of creatine phosphate in these fibres than the patients with dystrophia myotonica ( P < 0.03) and myotonia congenita ( P < 0.05). After 30 s bicycle ergometer exercises there was an increase in ATP in the ST muscle fibres of the patients with myotonia congenita, but in all other patient groups there was a decrease.