Cation transport in intact erythrocytes of hyperthyroid patients: role of the NaK-ATPase pump.
Studies of erythrocyte (RBC) cation fluxes and concentrations in hyperthyroid subjects  have recently been reported with the suggestion that Na-K ATPase activity was decreased. We have studied tha kinetics of total and ouabain-sensitive K+ uptake utilizing 86Rb as a tracer in the intact erythrocytes of 7 hyperthyroid subjects and compared the results of those of a healthy control population. We find total K+ transport is depressed in the RBC of hyperthyroid subjects. The Vmax for K+ transport for hyperthyroid subjects is 1.8 +/- 0.17 x 10(-4) mM K+/10(9) RBC/hour versus a control of 2.3 +/- 0.14 x 10(-4) mM K+/10(9) RBC/hour. This depression in Vmax is evident in spite of no significant differences in the Km for the system when hyperthyroid subjects (2.7 +/- 0.19 mM) are compared to controls (2.38 +/- 0.21 mM). Further, the depressed K+ transport appears to be the result of depressed ouabain--insensitive K+ transport. Although the percent of the ouabain-sensitive K+ transport is greater in the hyperthyroid subject (82.5%) versus controls (72.5%), this simply reflects a relative change in a system where total transport is dropping but the ouabain-sensitive component is remaining unchanged. None of these findings can be directly or indirectly related to thyroid hormone and it is suggested that the ion transport changes reflect factors independent of thyroid hormone.
D000293:Adolescent; D000328:Adult; D001692:Biological Transport; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006801:Humans; D006980:Hyperthyroidism / Q000097:blood*; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood*; D000254:Sodium-Potassium-Exchanging ATPase / Q000097:blood*
D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium