AJP - Regulatory, Integrative and Comparative Physiology, Vol 250, Issue 6 984-R990, Copyright © 1986 by American Physiological Society
Ionic requirements of peritubular taurine transport in Fundulus kidney
N. A. Wolff, D. F. Perlman and L. Goldstein
A peritubular mechanism for active taurine uptake, similar to that
previously found in the flounder, was demonstrated in killifish (Fundulus
heteroclitus) teased renal tubules. Other beta-amino acids and glycine
inhibited taurine transport. Uptake exhibited a nearly absolute requirement
for external Na+. The stoichiometric relationship between Na+ and taurine
was found to be 2:1. Medium Cl- markedly stimulated the Na+-dependent
taurine uptake, but none of the other small monovalent anions tested (NO3-,
Br-, SCN-) could substitute for Cl- in activating taurine transport. Cl-
replacement resulted in a significant decrease in V max, whereas the
affinity of the carrier for taurine appeared to be unaffected. In the
absence of Cl- the Na+ dependence of taurine influx was reduced to a
stoichiometric relationship of 1.4 Na+:1 taurine, indicating an effect of
Cl- on the binding of Na+ to the transport system. A model for Na+ -Cl-
-taurine cotransport is presented.
