Direct effect of inorganic mercury on citrate uptake by isolated rat renal brush border membrane vesicles.

Occupational exposure to mercury has long been associated with renal proximal injury and an increased incidence of proteinuria, as has such exposure to cadmium. Renal citrate excretion is very important with respect to acid-base balance since the metabolism of citrate generates three bicarbonate ions. In this study, we exposed isolated rat renal brush border membrane vesicles (BBMV) to mercury (Hg2+) and examined their citrate uptake characteristics. BBMV were prepared by the divalent cation precipitation method. Citrate uptake was measured by the Millipore rapid membrane filtration method. The preincubation of BBMV with 0.5 and 2 mM HgCl2 for 1 min significantly inhibited citrate uptake compared with that of BBMV without Hg preincubation. The analysis of the time course of citrate uptake during a 30-min preincubation of BBMV with 0.1 mM Hg2+ also revealed a significant reduction in the uptake compared with that of the control BBMV without preincubation. These findings indicate that the preincubation of BBMV with mercury results in a time- and concentration-dependent inhibition of citrate uptake.