1. Sodium efflux rate constants and intracellular sodium were measured in leucocytes from healthy volunteers in the presence and absence of the calcium antagonist verapamil hydrochloride. 2. Verapamil stimulated sodium pump activity and this effect was dependent on the presence of external calcium. 3. Verapamil has been reported to reverse the abnormality of sodium transport seen in leucocytes from patients with essential hypertension and the present study demonstrates that sodium pump activity in leucocytes from control subjects is also stimulated by exposure to verapamil in vitro. This direct cellular effect appears to be due to the calcium antagonist properties of the drug.
1. The transport of zinc has been studied in normal human leucocytes incubated in both a tissue culture medium and Krebs buffer. 2. 65 Zn influx is characterized by an initial rapid phase followed by a slower influx. 65 Zn influx is directly dependent upon the extracellular zinc concentration. 3. Net zinc influx could only be demonstrated in Krebs buffer at zinc concentrations in excess of 4.3 μmol/l and in tissue culture fluid at zinc concentrations in excess of 43.1 μmol/l. 4. A 65 Zn efflux rate constant of approximately 1.0 per h was observed in both 4.3 and 15.4 μmol of zinc/l of Krebs buffer or tissue culture fluid. 5. In a zero external zinc Krebs buffer the 65 Zn efflux rate constant fell to 0.57 per h and was accompanied by a small net zinc efflux.