Changes in kidney medullary phospholipid metabolism in the potassium-deficient rat. I.

Renal medullary phospholipids (PLs) increase rapidly in rats placed on a low potassium (K) diet. There is a unique pattern of morphologic change in renal medullary cells which parallels this biochemical alteration. Highly membranous multivesicular bodies (MVBs) appear in all cell types of the kidney medulla, and the number and size of these MVBs increase with further K depletion. Medullary PL levels are doubled in rats after 11 days on the low K diet and continued increase occurs with longer depletion. There are no major changes in the relative proportion of different medullary PL species with this increase. The rise in PL levels is quickly reversed by the addition of K to the low K diet of depleted rats. Potassium repletion returns renal medullary PL levels to normal values with a concomitant rapid loss of MVBs from medullary cells. Tissue slices of kidney medulla from rats in various stages of K depletion have been incubated with radioactive precursors of PL. These incubation studies indicate that the in vitro ability to incorporate label into PL is increased in medulla from K-depleted animals, suggesting that increased renal medullary PL synthesis causes the PL accumulation in K deficiency.