Letter: (Na plus K)-ATPase activity in cattle red cells

The response to potassium of the Na-K pump ATPase in low-K red blood cells from cattle at birth and in later life

It is shown that in low-K red blood cells of cattle the apparent affinity for K(1/Kapp K) at an inhibitory site of the Na-K ATPase increases markedly during the first 3 months of life. This site probably is the Na accepting site at the internal membrane surface and the change in Kapp K reflects an increase in KNa/KK, the ratio of the true dissociation constants. This effect may explain the concomitant fall in cellular K concentration.

Potassium transport and lipid composition in mammalian red blood cell membranes

Potassium influxes in red cells from eight species have been found to follow exponential relationship with membrane phosphatidylcholine and sphingomyelin content. This relationship with membrane phosphatidylcholine and sphingomyelin content. This relationship with membrane phospholipid patterns was found to exist with both ouabain sensitive and insensitive fraction of potassium transport. When published values of chloride and phosphate permeabilities were compared with potassium permeabilities, correlations were found in seven out of nine of the species studied. On the basis of these findings it appears that potassium, phosphate, and chloride permeabilities in red blood cells of most species are related to the membrane phosphatidylcholine and sphingomyelin content; that is, membrane permeabilities increase with increasing amounts of phosphatidylcholine and decrease with increasing amounts of sphingomyelin. These results indicate that the membrane lipid is an important factor in transport processes in mammalian red blood cells.