INHIBITION OF PINOCYTOSIS BY NICOTINE

¹ Department of Pharmacology, Georgetown University, Schools of Medicine and Dentistry, Washington, D.C.

The pinocytosis of invertase by sucrose-laden cultured mouse peritoneal macrophages was used as a model to study the effects of nicotine on pinocytosis. Sucrose-laden macrophages attached to glass coverslips were exposed to media containing invertase or invertase plus nicotine for 30 minutes. Cultures were then returned to control media to allow for the intravacuolar hydrolytic activity of pinocytosed invertase. The activity of invertase, which is indicated by the disappearance of sucrose vacuoles, was partially inhibited by nicotine tartrate at concentrations of 13.2 and 6.60 mM, but not at a concentration of 1.32 mM. Similar results were obtained with nicotine alkaloid but not with sodium tartrate. The apparent interference of the interaction of invertase with intracellular sucrose was confirmed by radiometric means in cells containing sucrose-²⁴C. Tetramethylammonium and hexamethonium ions also interfered with the invertase effect. Nicotine did not inhibit the activity of invertase in vitro. It is concluded that nicotine blocked the pinocytosis of the enzyme.