Vitamin D metabolism in adult rats at low and normal calcium intake and the effect of cadmium exposure.
1. Chromatography measurements indicated that adult rats converted 25-hydroxycholecalciferol into 1,25-dihydroxycholecalciferol at a lower rate than that reported earlier for young animals. In serum, less-polar metabolites were found which probably represented vitamin D esters and vitamin D3. 2. A low dietary intake of calcium resulted in an evident increase in the fraction corresponding to 1,25-dihydroxycholecalciferol in the kidneys and also in the intestinal mucosa and serum. 3. Inclusion of 0.67 mmol of cadmium/l of drinking water at a low dietary intake of calcium resulted in an increased accumulation of both cadmium and zinc in the kidneys and liver compared with values at a normal dietary calcium intake. 4. At a normal dietary calcium intake, cadmium exposure caused inhibited production of 1,25-dihydroxycholecalciferol by the kidneys and an increased accumulation of 24,25-dihydroxycholecalciferol, vitamin D3 and vitamin D esters in the serum. 5. The inhibitory effect of cadmium on the renal conversion of 25-hydroxycholecalciferol into 1,25-dihydroxycholecalciferol was almost completely counteracted by a simultaneous low dietary calcium intake. Cadmium-exposed, calcium-deficient animals also showed a maintained accumulation of 1,25-dihydroxycholecalciferol in the intestinal mucosa.
D000818:Animals; D002104:Cadmium / Q000378:metabolism / Q000494:pharmacology*; D002136:Calcium, Dietary / Q000378:metabolism*; D002850:Chromatography, Gel; D005260:Female; D006887:Hydroxycholecalciferols / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D051381:Rats; D014807:Vitamin D / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism
D002136:Calcium, Dietary; D006887:Hydroxycholecalciferols; D002104:Cadmium; D014807:Vitamin D; D015032:Zinc