Regulation of sodium influx and sodium, potassium pump activity by a sodium-hydrogen antiport in rat vascular smooth muscle.

1. The effects of Na-H antiport inhibitors on sodium influx, intracellular pH and Na,K-pump activity were examined in vascular smooth muscle from rats. 2. Amiloride and 5-(N-ethyl-N-isopropyl)amiloride inhibited Na accumulation following inhibition of the Na,K-pump. 3. Inhibition of Na influx was associated with a reduction in basal Na,K-pump activity and intracellular pH. 4. It is concluded that a Na-H antiport system in vascular smooth muscle regulates Na influx rate, contributes to intracellular pH regulation and influences basal levels of Na,K-pump activity.