MYOPHOSPHORYLASE DEFICIENCY ASSOCIATED WITH RHABDOMYOLYSIS AND EXERCISE INTOLERANCE IN 6 RELATED CHAROLAIS CATTLE

A Charolais calf presented to the Veterinary Medical Teaching Hospital with a history of recumbency following forced exercise, The calf was unable to stand, and had severe rhabdomyolysis, dehydration, and elect rolyte imbalance. Blood selenium concentrations were within normal lim its. A complete absence of histochemical staining for phosphorylase wa s apparent in muscle biopsies, Five other animals in the herd also had exercise intolerance and had a complete absence of phosphorylase stai ning in muscle biopsies, Biochemical analyses confirmed a deficiency o f myophosphorylase (range 0-0.3 mu mol/g per minute: normals 15-27) wi th normal to slightly elevated muscle glycogen concentrations. Pedigre es from all affected animals showed a common ancestor on the sire's an d dam's side of each phosphorylase-deficient animal, suggesting an aut osomal recessive transmission. Although myophosphorylase deficiency wa s described in humans (McArdle's disease) over 40 years ago, these cat tle represent the first animal model for this disease. (C) 1995 John W iley and Sons, Inc.