Possible Mechanisms for Dietary Molybdenum Toxicity in the Rat

Abstract

Weanling rats were fed 10% casein, semi-purified diets with and without added molybdenum, and nitrogen balance studies were conducted. Digestion and absorption of nitrogen were not affected by dietary molybdenum. Urinary nitrogen excretion was increased when molybdenum was included in the diets. For the first 3 weeks of feeding, urea plus ammonia excretion accounted for most of the increased nitrogen excretion and then an aminoaciduria developed which contributed significantly to the urinary nitrogen excretion. Elevated levels of urinary α-amino nitrogen were observed with an increased level of dietary molybdenum and with increased duration of molybdenum feeding. Urea plus ammonia excretion decreased concomitantly with the increased aminoaciduria. The hypothesis that dietary molybdenum inhibits some facet of protein synthesis is proposed and discussed in conjunction with these observations.