Park T, Rogers Q R, Morris J G, Chesney R W
Department of Physiological Sciences, University of California, Davis, 95616.
J Nutr. 1989 Oct;119(10):1452-60. doi: 10.1093/jn/119.10.1452.
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 microM to 16 +/- 5 microM and 1.7 +/- 0.5 microM in 1 and 6 wk, respectively. Feeding HT increased plasma taurine concentration to 350 +/- 116 microM in 1 wk. Compared to NT, taurine accumulation by BBM vesicles was significantly elevated after 4 wk of feeding OT and decreased after 2 wk or less of feeding HT (P less than 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 Vmax of 55 +/- 10, 123 +/- 24 or 39 +/- 7 pmol.mg protein-1.10 s-1 and a Km of 32 +/- 7, 16 +/- 2 or 37 +/- 8 microM, respectively. The differences in Vmax and Km were significant between NT and OT (P less than 0.05), but not significant between NT and HT (P greater than 0.05). Our results suggest that renal adaptation of the kitten to changes in dietary taurine occurs with modifications of both Vmax and Km of the taurine transport system.
使用近端肾小管刷状缘膜（BBM）囊泡评估小猫对饮食中牛磺酸摄入量改变的肾脏适应性。三组小猫适应了含有43.5%大豆蛋白的纯化饮食，其中一组不含牛磺酸（OT），一组含有0.15%牛磺酸（NT），另一组含有1.0%牛磺酸（HT）。喂食OT组小猫的血浆牛磺酸浓度在1周和6周时分别从104±25微摩尔/升降至16±5微摩尔/升和1.7±0.5微摩尔/升。喂食HT组小猫在1周时血浆牛磺酸浓度升高至350±116微摩尔/升。与NT组相比，喂食OT组4周后BBM囊泡对牛磺酸的积累显著升高，而喂食HT组2周或更短时间后则降低（P<0.05）。喂食OT组6周时出现最大肾脏适应性（与NT组相比，牛磺酸摄取/15秒增加206%），喂食HT组2周或更短时间时出现最大肾脏适应性（与NT组相比，牛磺酸摄取/15秒减少43%）。对喂食NT、OT（12周）或HT（10周）的四组小猫（每组16次测定）的肾皮质进行转运动力学评估，结果显示Vmax分别为55±10、123±24或39±7皮摩尔·毫克蛋白-1·10秒-1，Km分别为32±7、16±2或37±8微摩尔/升。NT组和OT组之间Vmax和Km的差异具有显著性（P<0.05），但NT组和HT组之间差异不显著（P>0.05）。我们的结果表明，小猫对饮食中牛磺酸变化的肾脏适应性是通过牛磺酸转运系统的Vmax和Km的改变而发生的。
