REVERSIBLE AND SELECTIVE ANTAGONISM BY SURAMIN OF ATP-ACTIVATED INWARD CURRENT IN PC12 PHEOCHROMOCYTOMA CELLS

1. The effects of suramin on an adenosine 5'-triphosphate (ATP)-activated inward current were investigated in PC12 phaeochromocytoma cells with whole-cell voltage-clamp techniques. 2. Suramin (30 to 300 μM) inhibited the ATP-activated current in a dose-dependent manner. The inhibitory effects were reversible and competitive. 3. Suramin also suppressed the current activated by adenosine 5'-O-(3-thiotriphosphate) but did not affect the current activated by nicotine. Suramin did not affect the suppression of a K current induced by methacholine. 4. The results suggest that suramin antagonizes the ATP-receptor-operated membrane current reversibly and selectively.