EFFECT OF HYPOKALEMIA ON THE ABUNDANCE OF HK-ALPHA(1) AND HK-ALPHA(2)PROTEIN IN THE RAT-KIDNEY

An H+-K+-adenosinetriphosphatase (H+-K+-ATPase) contributes to potassi um reabsorption by the collecting ducts of the rat kidney. mRNAs for t wo isoforms of the H+-K+-ATPase, HK alpha(1) and HK alpha(2), have bee n found in the rat kidney. To evaluate whether the HK alpha(1) and HK alpha(2) proteins are present in the rat kidney, microsomes enriched i n HK alpha(1) or HK alpha(2) were isolated using the MiniMac magnetic separation system with antibodies directed against either HK alpha(1) (HK 12.18) or HK alpha(2) (AS 31.7). Immunoblots of rat kidney microso mal protein isolated with HK 12.18 revealed a band similar to 94 kDa i n size that comigrated with the G1 fraction of the stomach. Immunoblot s of rat kidney microsomal protein isolated with AS 31.7 revealed a ba nd slightly greater than 94 kDa that comigrated with a band obtained f rom rat colonic microsomal protein. To examine the effect of perturbat ions in potassium metabolism, the abundance of the HK alpha(1) and HK alpha(2) isoforms was compared in rats fed a normal or potassium-defic ient diet. A low-potassium diet increased the abundance of HK alpha(2) , whereas that of HK alpha(1) was not altered. These data suggest that HK alpha(2) might be the isoform responsible for potassium conservati on by the kidney.