Effect of high-dose thiazide treatment and low-K diet on citrate uptake by rat renal brush border membrane vesicles (BBMV)

Abstract

In order to study the effect of high-dose thiazide treatment and low-K diet on citrate uptake by rat renal brush border membrane, we measured citrate uptake by rat renal brush border membrane vesicles (BBMV) and analyzed the acid-base balance of non-treated rats, high-dose thiazide-treated rats and low-K diet rats. Seven-week male Wistar rats (Jcl) were housed in metabolic cages, given 10 mg/Kg BW/day hydrochlorothiazide (HCTZ) by a gastric tube once a day for 3 weeks (high-dose thiazide treated rats) or a low-K diet for 3 weeks (low-K diet rats). Arterial blood was taken from the aorta and BBMV were prepared by the divalent cation precipitation method. Citrate uptake was measured by a Millipore rapid membrane filtration technique. High-dose thiazide treatment for 3 weeks showed a significant metabolic alkalosis and increase of urinary citrate excretion. However, it had no significant effect on citrate uptake by BBMV. On the other hand, low-K diet for 3 weeks showed significant hypokalemia, metabolic alkalosis and decrease in urinary citrate excretion. Moreover, it increased the maximal activity (Vmax) with no difference in citrate affinity (Km). These data suggested that urinary citrate excretion was more affected by the K depletion than by the acid-base balance.