Transport characteristics of [3H]-chlorpromazine across rat small intestinal brush border membrane.

The transport mechanism of chlorpromazine, a tertiary amine, has been investigated using brush border membrane vesicles isolated from rat small intestine. Chlorpromazine was taken up rapidly by the vesicles the uptake being mainly due to binding to the membrane. The transport of chlorpromazine into the intravesicular space was facilitated by the transmembrane electrical potential difference (inside negative) induced by valinomycin or sodium thiocyanate. This facilitating effect was observed only when the transmembrane electrical potential difference was induced after chlorpromazine uptake had reached a steady state. In the initial phase of chlorpromazine uptake, there was no effect. Therefore, it is suggested that both rapid binding to brush border membrane and transmembrane electrical potential difference (inside negative) across the membrane plays a significant role in the transport processes of chlorpromazine through the intestinal epithelium.