Involvement of Phospholipids in Rb+ Transport by Kidney Cortex Tubules

The relationship between the phospholipid structure of renal cortical tubules and their ability to sequester Rb+ was investigated. When the isolated cortical tubules were treated with low levels of commercial phospholipase C from Clostridium welchii, there was very little destruction of the tubular phospholipid but the sequestration of Rb+ was markedly curtailed. Since such treatment does not affect Rb+ efflux, it appears that phospholipase C treatment acts by inhibiting the uptake of Rb+. The evidence presented indicates that phospholipase C, rather than a contaminant of the preparation or an inhibitory product of the enzyme reaction, depresses Rb+ uptake by its action on the cell membrane phospholipids. Evidence is also presented that indicates that the inhibition of Rb+ uptake is not the result of widespread destruction of the cell. Phospholipase C treatment, which markedly decreases Rb+ uptake, does not depress galactose and 2-deoxygalactose uptake by the cortical tubules. It is concluded that a phospholipid structure (or structures) on the outer surface of the plasma membrane is involved in the uptake of Rb+ by renal cortical cells.