SERCA1 activity in the Congenital Pseudo-myotonia of Chianina cattle

The contraction and relaxation of skeletal muscle is regulated by Ca release from sarcoplasmic reticulum (SR). The uptake of Ca into the lumen of SR, allowing relaxation, is mediated by a sarco-endoplasmic reticulum Ca-ATPase (SERCA). In the last years, a disorder of skeletal muscle function was described in some bovine specimens of Chianina breed. Chianina is one of the most important Italian breed for meat quality (fiorentina) and leather. Synthoms affect preferentially the musculature of the limbs and are exercise-induced stiffness and impaired skeletal muscle relaxation. This pathological condition appears us very similar to a skeletal muscle disorder described for the first time by Brody in 1969 in human patients. Brody ‘s disease is a rare inherited disease associated to a mutation in the ATP2A1 gene, encoding SERCA 1 isoform. From semimembranous pathological muscle of Chianina specimen, we prepared a crude microsomes membrane fraction (TM) in which the main markers of junctional (RyR) and non junctional SR (SERCA) are selectively enriched. TM fraction were used for determination of the ATPase activity of the SR calcium pump, assayed by a spectrophotometer method, measuring the ossidation of NADH at 340 nm, in the presence of calcium ionophore A23187. By comparison with control bovine muscle of the same species, ATPase activity of SERCA in pathological muscles resulted reduced of about 50% in two specimens and almost absent in other subjects. Immunoblotting results with antibodies against SERCA 1 isoform in the same fractions, confirmed the absence or reduction of expression of the Ca-pump in pathological animals. Our preliminary data suggests that the bovine skeletal muscle disorder might be related to human Brody’s disease and that bovine might be assumed as the animal model as porcine for malignant hyperthermia.