A histochemical study of changes observed in the mouse diaphragm after organophosphate poisoning.

A sublethal dose of sarin (GB, isopropyl methylphosphonofluoridate) was administered to mice. The animals were killed up to 28 d after dosing and frozen sections were made of the excised diaphragms which were stained using haematoxylin and eosin and a modified Gomori trichrome method. Muscle fibre degeneration and mononuclear infiltration were seen, notably at 24 h and 3 d. A number of histochemical procedures were carried out, including the GBHA procedure for ionized calcium. Calcium accumulation, seen at 4 h, was the earliest abnormality observed. All changes were rapidly regressing by 5 d and histological appearances were normal by 14 d. It was concluded that sarin produced myopathic changes preceded by calcium accumulation.