2,4-Dinitrophenol, muscle biopsy, and McArdle's disease.

Exercise is simulated in muscle biopsy preparations by using low concentrations of 2,4-dinitrophenol (DNP), which do not produce contracture or anatomic damage. The validity of this simulation is supported by (1) the biochemical effects of simultaneous muscle contraction and DNP are not additive, suggesting that exercise and DNP stress the same pathways; (2) the effects of increasing concentrations of DNP and increasing levels of stimulation are similar with an early drop in phosphocreatine, increasing lactate and inosine monophosphate (IMP), and a late fall in ATP levels; and (3) DNP provocation in a patient with McArdle's disease demonstrated an absence of lactate and high levels of IMP correlating with clinical findings. DNP provocation may be a simple way of studying metabolic pathways in neuromuscular diseases.