Identification of a high affinity taurine transporter which is not dependent on chloride

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Abstract
Taurine transport by lactating gerbil mammary tissue has been examined. Taurine uptake is, mediated by a high-affinity system which is specific for β-amino acids. The uptake of taurine is Na+-dependent but appears not to be obligatorly dependent upon Cl−. Thus, replacing Na+ with choline almost abolished taurine uptake. Substituting Cl− with NO3− had no effect whereas SCN− induced a small but significant increase in taurine influx. Taurine uptake was Na+-dependent under conditions where Cl− had been replaced with NO3−. However, it is apparent that the Na+-dependent taurine transport system requires the presence of a permeable anion because replacing Cl− with gluconate markedly reduced taurine uptake. Cell-swelling, induced by a hyposmotic challenge, increased the efflux of taurine from gerbil mammary tissue via a pathway sensitive to niflumic acid.