The question of chymase in cultured muscle cells.

An alkaline proteinase, identical to mast cell chymase, has been described by a number of laboratories as being associated with myofibrils extracted from adult rat skeletal muscle tissue. A more recent study has indicated that chymase may be an intrinsic protein in the rat myocyte. The present study of rat myogenic cell lines, using more stringent controls and a probe of more highly defined specificity, supports the view that (i) chymase originates from mast cells of the interstitium and (ii) chymase from mast cells becomes adsorbed to myofibrils of adult muscle during homogenization of this complex tissue.