Effect of Na, metabolic inhibitors and ATP on Ca movements in L cells

Abstract

1. The Ca movements in normal and ;ghost' L cells have been examined; all measurements were made using (45)Ca.2. Normal cells have a Ca concentration of about 1 m-mole/l. of cell volume, and exchange Ca in a complex way but with great rapidity; the time taken for the initial Ca(*) content to fall to half was less than 2 min.3. Poisoning normal cells with DNP 10(-3)M + IAA 10(-4)M causes a marked reduction in the Ca efflux, no change in Ca influx and an increase in total Ca.4. Variation in internal or external Na concentration does not alter the Ca fluxes or concentrations. Application of cyanide or ouabain and alteration of external K concentration had no effect on the Ca fluxes.5. The sulphydryl reagents, ethacrynic acid and N-ethylmaleimide (NEM), have a rapid and marked effect on reducing the Ca efflux.6. L cell ghosts previously poisoned with DNP+IAA have a low Ca efflux. When ATP or CTP is incorporated into such cells the Ca efflux becomes normal.7. An extra amount of phosphate is produced by L cell ghosts when pumping Ca. This is equivalent to the splitting of 1.8 moles of ATP per mole of Ca pumped.8. It is concluded that L cells have a Ca pump driven by ATP, and that Na has no effect on Ca movements in these cells.