The nature of the muscle-relaxing factor. I. An improved assay system.

Analysis of the effects of deoxycholate and benzalkonium chloride on granule relaxing activity, myofibril and glycerinated fiber responses to ATP, and the sensitivity of these actomyosin-containing systems to relaxing factors have established that it is possible to differentially inactivate intrinsic granule relaxing factor. It is therefore possible to use these agents to treat myofibrils and glycerinated muscle fibers so that they may be used for the assay of muscle-relaxing factor preparations. The destruction of intrinsic relaxing factor can be produced by treating actomyosin with 1 mM deoxycholate or 0.005 per cent benzalkonium chloride for 5 minutes at room temperature.