Effect of dietary taurine on renal taurine transport by proximal tubule brush border membrane vesicles in the kitten

Renal adaptation of the kitten to altered dietary taurine intake was assessed using proximal tubule brush border membrane (BBM) vesicles. Three groups of kittens were adapted to purified diets containing 43.5% soy protein that were either taurine-free (OT) or contained 0.15% taurine (NT) or 1.0% taurine (HT). The plasma taurine concentration of the kittens fed OT decreased from 104 ± 25 μM to 16 ± 5 μM and 1.7 ± 0.5 μM in 1 and 6 wk, respectively. Feeding HT increased plasma taurine concentration to 350 ± 116 μM in 1 wk. Compared to NT, taurine accumulation by BB, vesicles was significantly elevated after 4 wk of feeding OT and decreased after 2 wk or less of feeding HT (P < 0.05). Maximum renal adaptation occurred by 6 wk of feeding OT (206% increase in taurine uptake/15 s compared to NT) and by 2 wk or less of feeding HT (43% decrease in taurine uptake/15 s compared to NT). Evaluation of transport kinetics using renal cortex from groups of four kittens (16 determinations) fed NT, OT (12 wk) or HT (10 wk) revealed a V(max) of 55 ± 10, 123 ± 24 or 39 ± 7 pmol · mg protein^-1 · 10 s^-1 and a K(m) of 32 ± 7, 16 ± 2 or 37 ± 8 μM, respectively. The differences in V(max) and K(m) were significant between NT and OT (P < 0.05), but not significant between NT and HT (P > 0.05). Our results suggest that renal adaptation of the kitten to changes in dietary taurine occurs with modifications of both V(max) and K(m) of the taurine transport system.