Metabolism of vitamin D3-3H in human subjects: distribution in blood, bile, feces, and urine.
Vitamin D(3)-(3)H has been administered intravenously to seven normal subjects, three patients with biliary fistulas, and four patients with cirrhosis. Plasma D(3)-(3)H half-times normally ranged from 20 to 30 hours. in vivo evidence that a metabolic transformation of vitamin D occurs was obtained, and a polar biologically active vitamin D metabolite was isolated from plasma. Urinary radioactivity averaged 2.4% of the administered dose for the 48-hour period after infusion, and all the excreted radioactivity represented chemically altered metabolites of vitamin D. The metabolites in urine were mainly water-soluble, with 26% in conjugated form. From 3 to 6% of the injected radioactivity was excreted in the bile of subjects with T-tube drainage and 5% in the feces of patients having no T-tube. The pattern of fecal and biliary radioactivity suggested that the passage of vitamin D and its metabolites from bile into the intestine represents an essential stage for the fecal excretion of vitamin D metabolites in man. Abnormally slow plasma disappearance of vitamin D(3)-(3)H in patients with cirrhosis was associated with a significant decrease in the quantity and rate of glucuronide metabolite excretion in the urine.
D000328:Adult; D000818:Animals; D001646:Bile / Q000032:analysis; D001658:Biliary Fistula / Q000378:metabolism; D001681:Biological Assay; D002762:Cholecalciferol / Q000097:blood / Q000378:metabolism* / Q000652:urine; D002845:Chromatography; D005243:Feces / Q000032:analysis; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D008103:Liver Cirrhosis / Q000378:metabolism; D008297:Male; D011200:Poultry; D051381:Rats; D014316:Tritium; D014807:Vitamin D / Q000378:metabolism
D014316:Tritium; D014807:Vitamin D; D002762:Cholecalciferol