Kinetics of Red Cell Na⁺ and K⁺ Transport in Prague Hypertensive Rats

Abstract

Kinetics of ouabain-sensitive, furosemide-sensitive (FS), bumetanide-sensitive (BS) and -resistant Na⁺ and K⁺ transport were studied in erythrocytes of Prague hypertensive rats (PHR) and Prague normotensive rats (PNR). Maximal transport rates (V_max) and apparent affinities for either intracellular Na⁺ or extracellular K⁺ (replaced by Rb⁺) were determined in red cells in which Na⁺ content varied around the physiological range and that were incubated in Na⁺ media. No major differences between PHR and PNR were disclosed in the kinetics of ion transport mediated by the Na⁺-K⁺ pump or BS inward Na⁺-K⁺ cotransport. FS Rb⁺ uptake was higher (due to a greater V_max) in red cells of PHR as compared to PNR. In cells with a lowered Na⁺ content this elevation of FS Rb⁺ uptake was largely due to an augmented K⁺-Cl⁻ cotransport which exhibits a low affinity for Rb⁺_o and is blocked by 1 mM furosemide but not by 10 μM bumetanide. Red cells of PHR and PNR strains did not differ in either Na⁺ or Rb⁺ leaks. A slight increase of red cell Na⁺ content in PHR was evaluated in terms of the pump-leak concept. The present study did not reveal any obvious kinetic abnormalities of red cell cation transport the presence of which in tissues involved in blood pressure regulation would favor the development or the maintenance of genetic hypertension in PHR.

Key Words:

• Na⁺-K⁺ pump
• K⁺-Cl⁻ and Na⁺-K⁺-2Cl⁻ cotransport
• cation leaks
• furosemide
• bumetanide