MOLYBDENUM UPTAKE THROUGH THE ANION-EXCHANGER IN HUMAN ERYTHROCYTES

Human red blood cells were incubated in the presence of Na2MoO4 and th e initial rate of molybdenum uptake was measured by using inductively coupled plasma emission spectroscopy. About 99% of molybdenum uptake w as inhibited by DIDS or by SITS. DIDS-sensitive molybdenum uptake was inhibited by external chloride, bicarbonate, sulphate and phosphate in the range of concentrations previously described for anion carrier fl uxes. Trace elements, previously described to be translocated by the a nion carrier, i. e. copper, zinc and cadmium, slightly inhibited molyb denum uptake. Molybdenum uptake was strongly stimulated by acidificati on, suggesting that the monovalent HMoO4- anion species, which is form ed in acidic media (pK almost-equal-to 4.1), can be more rapidly trans located than the divalent anion complex MoO42-, which is the predomina nt form at physiological pH. In conclusion, the anion carrier can cata lyse rapid molybdenum movements across red cells membranes. This suppo rts previous reports of an enterohepatic circulation of molybdenum, wi th red blood cells acting as molybdenum carrier between the intestine and the liver.