Quantitation of myonecrosis induced by myotoxin a from prairie rattlesnake (Crotalus viridis viridis) venom

Using a pure myotoxin (myotoxin a) isolated from prairie rattlesnake Crotalus viridis viridis) venom, a comparison between two methods for quantitating myonecrosis in mice was made. Measurement of creatine kinase (CK) levels in the plasma showed two peaks in CK levels after myotoxin injection, whereas measurement by histological assay (vacuolation index) showed only one peak. The first peak in CK levels at 3 hr after injection did not correlate with a high vacuolation index, but did correlate with contraction of muscle induced by the toxin. However, there was good correlation between the two methods at 6, 12, 24, 48 and 72 hr after injection, at which time the muscle cells were necrotic. In the case of the first CK peak this method might be measuring contraction of the muscle, but the second peak was probably measuring altered permeability of the sarcolemma since vacuolation, i.e. swelling of sarcoplasmic reticulum, did follow. High plasma CK levels usually preceded high vacuolation indexes, indicating that CK release due to altered sarcolemma permeability preceded vacuolation. Caution should be taken when using plasma CK levels to estimate the quantity of necrotic muscle cells, so as to insure that pathologic and not physiologic changes are being measured.