An interaction between selenate and a sulfate transporter in the lactating rat mammary gland

The efficacy of selenate and other divalent anions to stimulate the efflux of radiolabeled sulfate from lactating rat mammary tissue slices has been examined. Both selenate and sulfate markedly increased the fractional release of sulfate via a system that is temperature-sensitive and sensitive to the anion-exchange inhibitor DIDS. The effect of selenate on sulfate efflux was saturable with an apparent affinity constant of approximately 0.27 mM. In addition, molybdate and thiosulfate were also found to increase sulfate efflux from the trans-aspect. It is concluded that sulfate and selenate share a pathway for transport in the lactating rat mammary gland.