Ion pumps in the renal tubule.

Biochemical studies of renal tissue have so far not shown the presence of any active pump mechanism other than Na-K-ATPase. In this review of possible transport mechanisms for the ions Na, K, H, Cl, and HCO3, it is suggested that transport of these ions can be coupled to ATPase by conductance (uniport) processes or by ion gradients by co-transport (symport) or countertransport (antiport) systems. These may be neutral or electrogenic. Accordingly, the function of any region of the tubule will be determined by the porter(s) present in the apical or basal-lateral membrane, and by the Na-K-ATPase located almost exclusively in the basal-lateral membrane. Future research in this area will probably define these porters in vesicles isolated from specific cell types of the kidney.