Vitamin D balance and distribution in rats given a massive dose of ergocalciferol: Part I. Experimental results

Abstract

A massive dose of ergocalciferol (40,000 I.U.) was given per os to groups of weanling rachitic rats and on each of the 4 succeeding days the pooled livers, intestines (minus contents), the remainder of the carcasses, the feces and the urine were assayed biologically for vit. D. The assays were performed on freeze-dried, and fresh material. There was no evidence that loss of the vit. occurred on freeze-drying or storage. Little or no vit. D was detected in rachitic undosed animals. The estimates of the vit. D content of the body of rats receiving calciferol were 2380, 1230, 1260 and 940 I. U. on the 4 consecutive days, respectively. The decrease on the 2d day after dosing was mainly due to a fall in the vit. in the liver, from a value of 1440 to 510 I. U., a level subsequently maintained. The intestinal tissue showed a steady decrease from 250 on the 1st, to 40 I. U. on the 4th day. The remainder of the carcass maintained a level of about 600 I. U. throughout the exptl. period. It appeared that the liver was the main site of deposition. No significant transfer of the vit. from liver to other tissues of the body was observed within the period studied. The estimated fecal excretion of vit. D which was 4860 I. U. on the 1st day decreased to 1380, 200 and 30 I. U. on the subsequent days. No vit. D was found in urine, assayed as such or as the ether extract of urine hydrolyzed with concentrated HC1. About 23% of the dose was accounted for. The fate of the remainder of the ingested vit. is not known. It is assumed that it is converted into products having no antirachitic activity.