Dependence of fluid-phase pinocytosis in arterial smooth-muscle cells on temperature, cellular ATP concentration and the cytoskeletal system.

125I-labelled poly(vinylpyrrolidone) was used as a marker of fluid-phase pinocytosis in cultured pig arterial smooth-muscle cells. The rate of pinocytosis was temperature-dependent. A decrease in cellular ATP concentrations as a result of inhibition of either glycolysis or oxidative phosphorylation was associated with a similar decrease in pinocytosis. A microfibrillar-disruptive agent, cytochalasin B, caused a concentration-dependent stimulation of pinocytosis, whereas the microtubular-disruptive agents colchicine and vinblastine decreased pinocytosis to approximately half of control values at all concentrations used. These results indicate that fluid-phase pinocytosis in smooth-muscle cells is dependent on a continuing supply of energy and the integrity of the microtubules. Furthermore, microfilaments appear to exert a certain degree of constraint on pinocytosis, possibly by restricting invagination of the plasma membrane.