Glucocorticoid-induced alterations in the sodium potassium pump of the human erythrocyte.
To evaluate the effects of glucocorticoids on the Na-K pump in human subjects, were evaluated the intracellular sodium and potassium, 42K influx across and the [3H]ouabain binding to cell membranes of intact human erythrocytes from a group of subjects taking glucocorticoids and a group of normal subjects. Intracellular sodium concentration was lower (7.2 +/- 0.4 vs. 10.9 +/- 0.2 mmol/liter cell water) and intracellular potassium concentration higher (149.8 +/- 1.5 vs. 137.2 +/- 1.2 mmol/liter cell water) in erythrocytes from steroid-treated patients. In spite of a significantly decrease intracellular sodium which normally diminishes ouabain-sensitive 42K influx, the ouabain-sensitive K influx was unchanged in erythrocytes from the steroid-treated group. Maximum [3H]ouabain binding was markedly higher in the steroid-treated group (835 +/- 44 vs. 449 +/- 11 sites/cell). There was close linear correlation between [3H]ouabain binding and inhibition of K pump, suggesting the specificity of ouabain binding to Na-K pump sites on the cell membrane. Association kinetics for ouabain were similar in the two groups despite the marked difference in the amount of [3H]ouabain binding. External potassium concentration required for half-maximum ouabain-sensitive K influx was identical in the two groups. Thus, the additional Na-K pump sites in the steroid-treated group were qualitatively similar to those in normals. These results suggest that administration of glucocorticoids leads to an increase in the number of Na-K pump sites. The increase in the number of Na-K pump sites may explain the low levels of intracellular sodium and higher cell potassium observed in steroid-treated subjects.
D000328:Adult; D000368:Aged; D004905:Erythrocyte Aging; D004910:Erythrocyte Membrane / Q000201:enzymology*; D004912:Erythrocytes / Q000187:drug effects* / Q000201:enzymology*; D005260:Female; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008776:Methylprednisolone Hemisuccinate / Q000494:pharmacology; D008875:Middle Aged; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000097:blood*
D005938:Glucocorticoids; D010042:Ouabain; D008776:Methylprednisolone Hemisuccinate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium