EFFECTS OF BILE-DUCT LIGATION ON CALCIUM EXCRETION IN THE RAT

In an earlier study we showed that bile duct-ligated rats were highly susceptible to gentamicin nephrotoxicity and that oral calcium adminis tration had a pronounced protective effect. The mechanism by which thi s occurs is unclear. Because cations compete with gentamicin for tubul e binding sites, it has been suggested that the increased susceptibili ty of the kidney to gentamicin after bile duct ligation might result f rom decreased cation excretion. The aim of this study was to determine the effect of bile duct ligation on calcium excretion in relation to overall renal function. Male Sprague-Dawley rats underwent bile duct l igation and division. Pair fed sham-operated rats served as controls. Metabolic and clearance studies were carried out at 3, 5, 7, 14 and 21 days after surgery. Urine output was higher in bile duct-ligated rats , and they excreted more calcium at 3, 5, 7 and 14 days, while excreti ng less sodium than controls. We conclude that after bile duct ligatio n, there is increased calcium excretion, which is independent of the a bnormality in sodium excretion. Enhanced nephrotoxicity with aminoglyc osides in the bile duct-ligated rat model cannot be explained by decre ased calcium excretion.