Hypertaurinuria in the C57BL/6J mouse: altered transport at the renal basolateral membrane

The C57BL/6J mouse is an inbred strain with selective hypertaurinuria. C3H/HeJ mice (control) and C57BL/6J mice have comparable values for plasma taurine and renal creatinine clearance but significantly different fractional taurine excretion: C3H mice, 0.15 +/- 0.03; C57BL mice, 0.44 +/- 0.08 (P less than 0.01). C57BL mice fed control diet have significantly higher renal cortex taurine (11.5 +/- 0.4 mumol/g wet wt, mean +/- SE) relative to C3H mice (10.5 +/- 0.5 mumol/g, P less than 0.05); the difference is magnified when mice are fed low protein or low sulfur amino acid diet and experience renal adaptation with enhanced taurine transport at the luminal membrane (P less than 0.01). Taurine transport by purified brush border membrane vesicles is similar in the two strains fed control diet. On the other hand, renal cortex slices show the following differences: 1) net uptake of taurine at 0.11 mM is lower in C57BL slices at initial rates and at steady state; 2) the difference in uptake between strains is magnified in the presence of phlorizin, an inhibitor of taurine efflux; 3) efflux of taurine from preloaded slices is less per unit time in C57BL mice; and 4) uptake differences are specific for taurine. These findings are not accountable to differences in taurine oxidation, slice weight, or water spaces. They indicate that hypertaurinuria in the C57BL/6J strain is a function of decreased basolateral membrane permeability to taurine at physiologic concentrations.