[Effect of thiazide on urinary citrate excretion]

In order to study the effect of thiazide on urinary citrate excretion, we measured sodium dependent citrate uptake by rat renal cortical brush border membrane vesicles (BBMVs) and analyzed acid-base balance with or without thiazide treatment. 5-weeks male Wistar rats (Jcl) were housed in metabolic cages, given 0.1 mg/100 g BW/day hydrochlorothiazide (HCTZ) by a gastric tube once a day for 3 weeks (thiazide treated rats). Arterial blood was taken from aorta and BBMVs were prepared with divalent cation precipitation method. Citrate uptake was measured by a Millipore rapid membrane filtration technique. Oral treatment of HCTZ for 3 weeks showed a significant increase of urinary citrate excretion in both concentration and daily excretion. The sodium dependent citrate transport was observed in rat renal brush border membrane (BBM). But no significant effect of oral HCTZ was observed on acid base balance and sodium dependent citrate uptake in rat renal BBM. These data suggested that the stimulative effect of thiazide on citrate excretion was not via sodium dependent citrate transport in rat renal BBM.