Element concentrations of renal and hepatic cells under potassium depletion

Abstract

The effect of dietary potassium depletion on nuclear and cytoplasmic element concentrations in cortical renal tubular cells and hepatocytes was investigated using electron microprobe analysis. Significant differences in sodium and potassium concentrations between nucleus and cytoplasm were not detected either under control or under potassium-depleted conditions. Potassium depletion for at least 14 days resulted in a decrease in plasma potassium concentration from 4.4 ± 0.1 to 2.0 ± 0.1 mmoles.liter-1. There was a fall in cellular potassium from 151.6 ± 3.5 to 120.2 ± 2.1 in distal tubular cells, from 150.1 ± 2.6 to 117.7 ± 1.2 in proximal tubular cells, and from 140.6 ± 1.3 to 128.0 ± 1.3 mmoles.kg-1 of wet wt in hepatocytes. The cellular chlorine concentrations fell from 19.9 ± 0.7 to 15.8 ± 0.3 and from 21.3 ± 0.4 to 17.2 ± 0.4 in proximal tubular and liver cells, respectively, but remained unchanged at 11.4 ± 0.7 and 11.0 ± 0.4 mmoles.kg-1 of wet wt in distal tubular cells. The intracellular sodium concentrations rose from 10.4 ± 0.7 to 15.8 ± 0.8, 19.1 ± 0.8 to 24.1 ± 0.7 and 14.1 ± 0.5 to 16.2 ± 0.6 mmoles.kg-1 of wet wt in distal tubular, proximal tubular and liver cells, respectively. This rise in cellular sodium was insufficient in any cell type to compensate for the loss of potassium. No significant differences were found in the cellular electrolyte concentrations of the various distal tubular cell types which are thought to be involved in either potassium reabsorption or secretion. The decrease in potassium concentrations in distal tubular cells by about 20% does not seem sufficient to explain the marked fall in urinary potassium excretion.