Sodium exchange and distribution in the isolated heart of the normal dog

Abstract

Sodium exchange was studied in the isolated normal dog heart with the aid of a Na²⁴ tracer technique. Transcellular sodium exchange was calculated to be 0.04 mEq/kg/beat. The results are consistent with the concept of sodium influx into the cell during the spike potential, relative membrane impermeability to sodium in the membrane resting state, and a membrane capacity of about 10 µf/cm².