Studies on renal adaptation to altered dietary amino acid intake: reduced renal cortex taurine content increases the Vmax of taurine uptake by brush border membrane vesicles.
Rats were placed on a normal taurine diet (NTD), low taurine diet (LTD) or a high taurine diet (HTD) for 14 days. beta-Alanine was fed to half of the animals in each group and resulted in a lowered renal cortex taurine content. Brush border membrane vesicle (BBMV) uptake of taurine was higher after beta-alanine feeding and was associated with an increase in Vmax of uptake. beta-Alanine feeding to HTD animals also altered the Km of uptake, possibly since the load of sulfur amino acids (6% of diet) was high. As a control, glycine (3%) feeding for 8 days along with each diet did not alter the plasma or renal cortex content; BBMV uptake as well as Km and Vmax of taurine accumulation were minimally altered. Accordingly, ingestion of a non-sulfur-containing alpha-amino acid did not change beta-amino acid transport. This study provides evidence that whole body taurine homeostasis is maintained in the presence of a taurine-depleting agent (beta-alanine feeding) by an increase in the number of Na(+)-taurine uptake sites.
Chesney
R W
RW
Department of Pediatrics, University of California, Davis, School of Medicine 95817.
Gusowski
N
N
Dabbagh
S
S
D000596:Amino Acids / Q000008:administration & dosage*; D000818:Animals; D004032:Diet; D005998:Glycine / Q000008:administration & dosage; D007668:Kidney / Q000187:drug effects*; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008871:Microvilli / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013654:Taurine / Q000378:metabolism*
D000596:Amino Acids; D013654:Taurine; D005998:Glycine