Interactions of phorbol esters with cellular membranes in vitro.

Esters of phorbol, a family of tumor-promoting agents, interact in vitro with cellular membranes. In CsCl equi librium density gradients, isotopically labeled phorbol didecanoate cosediments with microsomal and nuclear membranes prepared from rat liver. The interaction be tween these membranes and the promoting compound is enhanced in the presence of native or denatured DNA. Moreover, changes in membrane density and in the amounts of radioactive DNA associated in vitro with the membrane are seen in CsCl in the presence of several unlabeled phorbol esters. The possibility that alterations of cellular mem branes are related to tumor promotion is considered.