title: Ionic requirements of peritubular taurine transport in Fundulus kidney.
abstract: 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.
mesh_terms: D000818:Animals; D000838:Anions / Q000502:physiology*; D001692:Biological Transport / Q000187:drug effects; D001693:Biological Transport, Active / Q000187:drug effects; D005260:Female; D005399:Fishes / Q000378:metabolism*; D007684:Kidney Tubules / Q000187:drug effects / Q000378:metabolism*; D007695:Killifishes / Q000378:metabolism*; D008297:Male; D012964:Sodium / Q000502:physiology; D013654:Taurine / Q000378:metabolism*; D013861:Thiocyanates / Q000494:pharmacology
chemical_list: D000838:Anions; D013861:Thiocyanates; D013654:Taurine; D012964:Sodium; C031760:thiocyanate