Abstract
To understand the relaxation mechanism in blood cells, the microsomal fracton was prepared from leucocytes. In this leucocytic microsomal fracton (LMF), ATP-dependent and oxalate-enhanced Ca2+ uptake could be observed, and when LMF was added to the superprecipitation reaction system of leucocyte myosin B in the absence of EGTA, the superprecipitation was remarkably depressed. Evidences, showing that salyrgan inhibited Ca2+ uptake and ATPase activity of LMF whereas sodium azide did not exhibit any inhibitory effect on both functions, suggested that no mitochondrial fraction was contaminated in this microsomal fraction from leucocytes.
From our investigations including electron microscopic study, it was proved that a leucocyte had the microsomal fraction as a relaxing factor and its nature resembled the sarcoplasmic relaxing factor from the smooth muscle or the cardiac muscle.
