Influence of Excessive Amounts of Vit. D3 on Strontium-89 Metabolism in the Rat.

Abstract

Three experiments were conducted using weanling albino rats. In the first experiment, a series of diets containing 0 to 2,500,000 International Units (IU) vitamin D3/kg of diet were fed for 7 days before oral administration with 10 [mu]c Sr89. In the 2d 2 Ca deficient diets containing 0 and 200,000 IU vitamin D3/kg were supplemented with 0.75% Ca and/or an equivalent amount of Sr (1.64%). These were fed 6 days before oral administration of Sr89. In the 3d experiment, the influence of length of period of feeding (0 and 3 days before oral Sr89 administration) 2,500,000 IU vitamin D3/kg or 2.5 mg dihydrotachysterol/kg on Sr metabolism was ascertained. These experiments demonstrated that vitamin D3 exerted an effect on excretion of Sr89 by increasing absorption of Sr89 from the gut, by decreasing fecal and increasing urinary Sr89, providing either Ca or Sr is present in the diet. The efficiency with which vitamin D3 exerted this effect was governed by its concentration in the diet and by the length of time it was fed before administration of Sr89.