Renal handling of taurine in marine fish

Net renal tubular excretion of taurine was demonstrated by clearance techniques in the dogfish, Squalus acanthias; the little skate, Raja erinacea; and in the winter flounder, Pseudopleuronectes americanus. Dogfish acclimated to 70% seawater had increased renal excretion of taurine resulting from higher glomerular filtration rates of taurine as well as from increased rats of tubular secretion. Tubular secretion of taurine prevailed in the dogfish and flounders measured, whereas it occurred in only 30% of the population of skates where tubular reabsorption predominated. Taurine uptake into incubated dogfish thin kidney slices was investigated. Uptake occurs mainly across the peritubular membrane, is carrier mediated, dependent on metabolic energy, and completely inhibited by ouabain and low Na in the medium. The active transport of taurine is also inhibited by beta-alanine but not by alpha-aminoisobutyric acid, glycine, gamma-aminobutyric acid, PAH, or probenecid.