Enzyme-linked immunosorbent assay for myosin heavy chains in the horse

The content in slow and fast myosin heavy chains (MHC 1 and MHC 2) of 5 equine muscles was determined using an enzyme-linked immunosorbent assay. The results obtained with this immunoenzymatic method were compared with complementary techniques: electrophoresis and immunohistochemistry. Slices of masseter, diaphragm, tensor faciae latae, semitendinosus and cutaneus trunci were obtained from a 12-year-old saddle horse after slaughter. Muscular proteins were specifically extracted to be analysed by ELISA. The technique used 2 complimentary monoclonal antibodies (MAb). MAb 1 was prepared from a human atrium specimen that reacted specifically against MHC 1. Mab 2 was prepared from myosin of rabbit psoas muscle and reacted against MHC 2. The masseter muscle contained solely MHC 1 (100%) and this was confirmed by electrophoresis and immunohistochemistry. By contrast, the cutaneus trunci was very poor in MHC 1 (1.3%) and was entirely composed of MHC 2 (98.7%) which was confirmed by the other techniques. The diaphragm, tensor fasciae latae and semitendinosus contained 89, 40 and 2% of MHC 1, respectively. It was concluded that this ELISA method made it possible to measure a wide range of MHC contents in equine muscles with a good reproducibility. The results were consistent with those sf the other fibre typing techniques. Moreover, this immunoenzymatic method is less time consuming than histological techniques and therefore offers new perspectives for muscle fibre typing in the horse.