Effect of molybdenum on phosphorus metabolism

Reports are conflicting. The effect of molybdenum (1000 ppm) added to the diet of rats was to increase the tissue uptake of phosphorus thereby improving phosphorus metabolism [Hennaux et al., 1963]. However, molybdenum had little effect on the excretion of phosphorus by rats on a rachitogenic diet and did not affect the phosphorus metabolism [Kolomiitseva and Smolyar, 1969]. In another study with rats on a rachitogenic diet the effect of dietary molybdenum (25 and 100 mg of ammonium molybdate) during the pre-rachitic period (10 weeks) was to cause decreased excretion of phosphorus [Smolyar, 1967]. In the period of manifest rachitis 25 mg of ammonium molybdate had no effect whereas 100 mg caused an increase of up to 100 % in excretion of phosphorus. What seems clear is that the correct amount of supplemental molybdenum in the diets of experimental animals can cause decreased excretion of calcium and phosphorus and their increased deposition in bone. A similar effect of molybdenum has been observed in children and the effect is apparently enhanced by copper [Peive, 1968].

Hennaux, L., Burny, A., Nangniot, P., Mommer, R., Roderbourg, J. and Vanuytrecht, S., Bull. Inst. Agron. Sta. Rech. Gembloux, 1963, 31, 449.
Kolomiitseva, M. G. and Smolyar, V. I., Vop. Pitan., 1969, 28, 31.
Peive, Ya. V., (ed.), Biol. Rol Molibdena, Sb. Tr. Simp. 1968 (Publ. 1972), Nauka, Moscow, U.S.S.R., 207, 235.
Smolyar, V. I., Mikroelem. Sel. Khoz. Med., 1967, 3, 184.

Molybdenum markedly enhances the activity of certain phosphatase enzymes. In vitro phosphate esters (ATP, acetylphosphate) are rapidly hydrolysed in the presence of molybdate and in rats added dietary molybdenum (400-1200 ppm) caused an increase in liver alkaline phosphatase activity [van Reen, 1954] but a reduction in the activity of kidney and intestinal alkaline phosphatase activity [van Reen and Williams, 1956]. Oral administration of ammonium molybdate (0.5-50 mg/ kg) to rats and rabbits or exposure to MoO3 (7-130 mg/m3) for 4 h inhibited the activity of alkaline phosphatase in blood serum [Lukashev, 1973]. Chronically administered molybdenum (0.2-1.2 g/day) increased the activity of alkaline phosphatase in the blood of sheep [Grigoryan and Brutyan, 1968]. By contrast a Japanese patent cites sodium molybdate (and tungstate) as inhibitors for acid and alkaline phosphatases in preventing the dephosphorylation of nucleotides [Fujishima patent, 1970].

van Reen, R., Arch. Biochem. Biophys., 1954, 53, 77.
van Reen, R. and Williams, M. A., Proc. Soc. Exptl. Biol. Med., 1956, 91, 638.
van Reen, R. and Williams, M. A., Arch. Biochem. Biophys., 1956, 63, 1.
van Reen, R., J. Nutr., 1959, 68, 243.
Lukashev, A. A., Grig. Tr. Prof. Zabol., 1973, 12, 13.
Grigoryan, M. S. and Brutyan, A. S., Tr. Erevan. Zootekh.-Vet. Inst., 1968, 29, 57, 61.
Grigoryan, M. S., Tatevosyan-Markaryan, L. G., and Asmangulyan, T. A., Biol. Zh. Arm., 1969, 22, 102.
Fujishima, T., Japan patent, 1970, 06, 869.