Effect of thiomolybdate and ammonium molybdate in pregnant guinea pigs and their offspring.

Groups of eight guinea pigs and their offspring were given drinking water containing molybdenum as ammonium molybdate (AM) or thiomolybdate (TM) throughout and subsequent to pregnancy. All adult females had oestrous cycles and conception rates were unaffected. Fetal death was common in groups given the high dose of TM. The concentration of copper in liver was reduced in all groups at all ages except for pups killed at birth from animals given AM. The concentration of molybdenum was elevated in liver and kidney of all groups and was statistically significant in the majority. The concentration in plasma of copper, molybdenum and copper insoluble in trichloroacetic acid was elevated in all groups. Superoxide dismutase activity was significantly reduced in dams and six-week-old pups in which TM administration commenced before mating. Histological damage occurred in the pancreas of animals given AM or TM. The effects on the fetus and pancreas were considered to result from copper deficiency rather than molybdenum toxicity.