title: Molybdate and tungstate transfer by rat ileum. Competitive inhibition by sulphate.
abstract: For both MoO42- and WO42- the maximum rate of uptake by the small intestine of the rat (studied in vitro using the everted sac technique) occurs in the lower ileum. Kinetic constants, derived by a least squares procedure, are compared with those previously obtained for SO42- transport. For both V and Ka, SO42- greater than MoO42- greater than WO42-, with only small differences between sacs IV and V. Mutual inhibition of MoO42- and WO42- transport and inhibition of both by SO42- are competitive processes. This is shown by the generally good agreement between Ka values and derived Ki values and by V values in the presence and absence of the inhibiting species. The three ions SO42-, MoO42- and WO42- are probably transferred across the intestine by a common carrier system. Implications for the sulphate-molybdenum interaction in molybdosis are discussed.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001693:Biological Transport, Active; D003300:Copper / Q000494:pharmacology; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008982:Molybdenum / Q000378:metabolism*; D051381:Rats; D013431:Sulfates / Q000494:pharmacology*; D014414:Tungsten / Q000378:metabolism*
chemical_list: D013431:Sulfates; D003300:Copper; D008982:Molybdenum; D014414:Tungsten