Fig. 1.

Tyrphostin 23 slowed the kinetics of rapid endocytosis. Exocytosis and rapid endocytosis were monitored using the capacitance technique on whole-cell patch-clamped bovine adrenal chromaffin cells. A, Capacitance recording of a control cell that underwent exocytosis during stimulation. Rapid endocytosis began after a short plateau phase. B, Capacitance recording of a cell treated with 100 μm tyrphostin 23, a protein tyrosine kinase inhibitor. Exocytosis was similar to that in the control cell, but the plateau time was longer, and the fast time constant of rapid endocytosis was slower. Exponential fits to the data are indicated by the solid lines.