Pump In Human Red Cells Research Articles

Nucleotide requirements for sodium-sodium exchange catalysed by the sodium pump in human red cells.

1. Resealed red cell ghosts containing a variety of nucleoside triphosphates, or a mixture of tri- and diphosphates, were allowed to lose (24)Na into a 10 mM-K medium or a K-free high-Na medium in the presence and absence of ouabain.2. Only ATP supported a ouabain-sensitive Na:K exchange in the 10 mM-K medium, or a ouabain-sensitive Na:Na exchange in the K-free medium.3. Because of ATPase and adenylate kinase activity, it is difficult to control the levels of ATP and ADP inside resealed red cell ghosts. Some control was achieved by incorporating into the ghosts an ATP regenerating system consisting of creatine phosphate and creatine kinase.4. Measurements of (24)Na efflux from ghosts prepared in this way showed that ADP is required for the ouabain-sensitive exchange of Na that occurs in K-free high-Na media, but not for the normal exchange of Na for K that occurs in K-containing media.5. The significance of these findings is discussed.

The coupling of downhill ion movements associated with reversal of the sodium pump in human red cells.

1. Previous work on the incorporation of inorganic phosphate (P(i)) into ATP has suggested reversal of the chemical reactions of the Na pump in human red cells. A study has now been made of the associated movements of Na and K.2. The efflux of K, and the influx and efflux of Na were measured. When the Ringer was without K, the loss of cell K was inhibited by ouabain, and the ouabain-sensitive component of K efflux (0.36 mu-equiv.ml.(-1).hr(-1)) required external Na.3. The exchange of Na was also inhibited by ouabain. When influx and efflux of Na were measured simultaneously in K-free Ringer there was an excess of ouabain-sensitive influx over efflux of about 0.36 mu-equiv.ml.(-1).hr(-1). This difference balanced the ouabain-sensitive K efflux, and was not found with 10 mM-external K. The Na and K movements appear to be coupled and to be mediated by reversal of the Na pump.4. The net uptake of Na sensitive to ouabain was 0.38 mu-equiv.ml.(-1).hr(-1) for red cells incubated in K-free Ringer, and the net loss of K under the same conditions was 0.58 mu-equiv.ml.(-1).hr(-1) in rough keeping with the unidirectional flux values.5. Oligomycin decreased Na influx and efflux to the same extent as ouabain.6. There appears to be a coupled downhill movement of Na and K that is abolished both by inhibitors of the Na pump and by external K which promotes normal transport of Na outwards and K inwards.

Inheritance of an increased sodium pump in human red cells.

A mutation at a control gene site may explain the appearance of both more sodium pump and a greater sodium leak in the red cells of patients with hereditary spherocytosis.