Intracellular sodium concentration and transport in red cells in essential hypertension, hyperthyroidism, pregnancy and hypokalemia.
Intracellular sodium content ([Nai]), ouabain-sensitive ('Na-K ATPase') and ouabain-insensitive ('passive permeability') sodium efflux, Na-K cotransport and Na-Li ('Na-Na') countertransport were estimated in erythrocytes in 39 control subjects, 20 patients with essential hypertension, 14 patients with hypokalemia of renal or unknown etiology, 13 hyperthyroid patients and 19 pregnant women. In normokalemic essential hypertension there was only a moderate, but significant elevation of the activity of the Na-Li countertransport system. In the group of patients with hypokalemia, there was a significant increase of [Nai], ouabain-insensitive sodium efflux and Na-Li countertransport. In hyperthyroidism, a marked decrease of Na-Li countertransport was associated with a marked elevation of [Nai], in pregnancy an elevation of the Na-Li countertransport with a [Nai] 43% lower than the control values. The ouabain-sensitive sodium efflux was elevated in hyperthyroidism and hypokalemia, in which [Nai] was increased. In the control subjects there was a positive linear correlation between ouabain-sensitive sodium efflux and [Nai]. The sodium component of the Na-K cotransport was decreased to about one third of the unchanged furosemide-sensitive potassium component during pregnancy.


CONCLUSIONS
The changes of cellular sodium metabolism in essential hypertension are of minor degree as compared to those in the other conditions studied. Cellular sodium metabolism in blood cells is influenced by thyroid hormones and metabolic disorders. Na-Li countertransport, i.e. Na-Na countertransport, seems to be involved in the regulation of [Nai]: an increase of its activity diminishes [Nai] (pregnancy); a decrease elevates [Nai] (hyperthyroidism). Ouabain-sensitive sodium efflux, i.e. 'Na-K ATPase', is mainly regulated by its substrate, [Nai].
D000328:Adult; D001692:Biological Transport / Q000187:drug effects; D004912:Erythrocytes / Q000201:enzymology / Q000378:metabolism*; D005260:Female; D006801:Humans; D006973:Hypertension / Q000097:blood*; D006980:Hyperthyroidism / Q000097:blood*; D007008:Hypokalemia / Q000097:blood*; D008094:Lithium / Q000378:metabolism; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011247:Pregnancy; D012964:Sodium / Q000032:analysis / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis
D010042:Ouabain; D008094:Lithium; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase