Isethionate and taurine transport sites at brain cell membranes: influx studies with brain slices

The influx of [14C]isethionate (ISA) into rat brain slices was studied with and without taurine. This influx was relatively rapid, but took place largely by a non-saturable, passive mechanism, which transferred much less ISA into the brain cells than taurine. Taurine inhibited the influx of ISA competitively (Km=50 and 100 μmol/l) at low ISA concentrations, and ISA that of taurine non-competitively (V=200 and 400–700 μmol×min−1×kg−1 wet weight) at high taurine concentrations. It thus appears that ISA and taurine may have a small number of common transport sites at brain cell membranes, but these are apparently of little significance for the total transport of ISA.