Detection of actomyosin-type protein at the surface of dissociated embryonic chick cells.

Abstract

WE have previously shown1 that antibodies prepared against smooth muscle actomyosin and capable of reacting with fibroblasts of connective tissue and with thrombocytes (platelets) markedly reduced the aggregative competence of embryonic chick muscle and liver cells. These antibodies were type specific and did not react with skeletal or cardiac striated muscle actomyosin nor with the (Na+,K+,Mg2+)-ATPase from human erythrocyte ghosts2. The same antibodies blocked the activity of the Ca2+-dependent myosin ATPase of smooth muscle actomyosin3. Antibodies directed against striated muscle actomyosin and capable of blocking the activity of the Ca2+-dependent ATPase of this protein did not produce the aggregation-inhibitory effect. This led to the suggestion that the effect was the result of the antibodies against smooth muscle actomyosin reacting with an actomyosin of similar type at the surface of the muscle and liver cells1.