Uptake of [3H]-nicotine and [3H]-noradrenaline by cultured chromaffin cells

Abstract

Three day-old cultured bovine adrenal chromaffin cells incubated at room temperature with Krebs-HEPES solution containing different concentrations of [3H]-nicotine, took up and retained increasing amounts of the drug by a mechanism that did not saturate. Concentrations of cold nicotine as high as 100 microM did not alter the amount of [3H]-nicotine retained by cells. Imipramine, cocaine, tetracaine or mecamylamine, at concentrations (10 microM) that blocked the catecholamine secretory effects of nicotine completely, did not modify the uptake of [3H]-nicotine. Both imipramine and cocaine drastically inhibited [3H]-noradrenaline uptake by cells in a concentration-dependent manner (IC50S of 0.08 and 1 microM, respectively). These data indicate that the secretory effects of nicotine are not coupled to its previous uptake into cells, and are evidence in favour of a site of action for nicotine located in or at the surface of the chromaffin cell membrane.