Sulphate transport by rat ileum. Effect of molybdate and other anions

Kinetic constants for SO4-2- transport by upper and lower rat ileum in vitro have been determined by computer fitting of rate vs concentration data obtained using the everted sac technique. MoO-4-2- inhibition of this transport is competitive, and kinetic constants for the inhibition were similarly determined. Transport is also inhibited by the anions WO4-2-, S2O3-2- and SeO4-2-, in the order S2O3-2- greater than SeO4-2- greater than or equal to MoO4-2- greater than WO4-2-. These anions have no effect on the transport of L-valine. Low SO4-2- transport rates were observed in sacs from animals fed a high-molybdenum diet. The significance of the results with respect to the problem of molybdate toxicity in animals is discussed, and related to the known protective effect of SO4-2-.