Determination of C14 and H3 in biological samples by Schöniger combustion and liquid scintillation techniques

164

Summary. Vitamin D8-3H has been administered intravenously to seven normal subjects, three patients with biliary fistulas, and four patients with cirrhosis. Plasma D3-3H 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 D3-3H in patients with cirrhosis was associated with a significant decrease in the quantity and rate of glucuronide metabolite excretion in the urine.

Section: Methodsmentioning

confidence: 99%

Metabolism of Vitamin D3-3H in Human Subjects: Distribution in Blood, Bile, Feces, and Urine*

Avioli¹,

Lee²,

McDonald³

et al. 1967

164

“…General methods Total fecal radioactivity was determined by the ignition method of Kelly, Peets, Gordon, and Buyske (6). Isotope counting was carried out in a Packard Tri-Carb scintillation counter, using an internal standard for quench correction.…”

Section: Methodsmentioning

confidence: 99%

Sterol Balance in Man as Plasma Cholesterol Concentrations Are Altered by Exchanges of Dietary Fats*

Spritz¹,

Ahrens²,

Grundy³

1965

146

Although the hypocholesteremic effect of unsaturated dietary fats has been repeatedly demonstrated, the mechanism underlying this effect is by no means clear. Four possibilities exist: 1) decreased cholesterol synthesis, 2) increased excretion of cholesterol or its metabolites, or both, 3) shift of plasma cholesterol to some other tissue(s), or 4) some combination of these factors.In a previous study of a single patient in this hospital (2) significantly increased excretion of neutral but not acidic fecal sterols was demonstrated when unsaturated fat replaced saturated fat in the diet. The present study extends that single experience to five studies in four other patients and utilizes a different and more generally useful methodology.An adequate evaluation of steroid 1 excretion depends first on devising a satisfactory procedure for quantitative isolation of fecal neutral steroids and simultaneously of other metabolic end products, notably the fecal bile acids; and second, on measuring accurately these excretion products by means that take into account the numerous chemical forms of these excretion products, some of which are still not identified.

“…As already described, (7,26) plasma, liver, and the two target tissues of vitamin D action, bones and small intestines, were analyzed for total tritium content after combustion analysis (29) and after lipid extraction in chloroform-methanol-water system (30). The "chloroform-soluble" metabolites of vitamin Da were separated by chromatography on silicic acid' columns (55 X 1.5 cm).…”

Section: Introductionmentioning

confidence: 99%

“Activation” of vitamin D by the liver

Ponchon¹,

Kennan²,

DeLuca³

1969

363

130