Clearance from Plasma and Excretion in Urine, Faeces and Bile of an Intravenous Dose of Tritiated Vitamin K₁ in Man

Abstract

S ummary Vitamin K 1 ‐ 3 H (1 mg; 12 μCi) was injected intravenously into three normal men, into three patients undergoing duodenal intubation and into a patient with T‐tube drainage of the common bile duct. In the normal subjects lipid‐soluble radioactivity (representing the injected vitamin K 1 ‐ 3 H) disappeared rapidly from the plasma: the clearance curve for the first 6 hr could be resolved graphically into two exponential functions, the first with a T ® of 20–24 min and the second with a T ® of 121–150 min: water‐soluble radioactivity, presumed to be metabolic products, appeared in the plasma within 30 min after injection, reached a peak at 2 hr and remained near this level for 24 hr. Of the injected radioactivity in the normal subjects, 19–26% was recovered in the urine after 3 days and 34–38% in the faeces after 5 days: most of the radioactive material in the faeces was lipid‐soluble, which on thin‐layer chromatography had a polarity between that of vitamin K 1 and vitamin K 1 γ‐lactone. In the patients undergoing duodenal intubation, radioactivity was detected in the duodenal juice within 20–40 min after injection of vitamin K 1 ‐ 3 H. Radioactivity was also detected in the bile in the patient with T‐tube drainage of the common bile duct. Most of the radioactivity in the duodenal juice and bile was water‐soluble. It seems likely that the radioactivity appearing in the faeces after intravenous injection of vitamin K 1 ‐ 3 H is derived from biliary excretion of water‐soluble conjugated metabolites which become lipid‐soluble by decon‐jugation during their passage through the bowel.