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Metabolism and Vitamin K Activity of cis Phylloquinone in Rats¹

Departments of Biochemistry, St. Louis University School of Medicine, St. Louis, Missouri 63104 and University of Rhode Island, Kingston, Rhode Island 02881

Preparations of phylloquinone enriched to contain about 80% of the cis form were separated from commercial synthetic phylloquinone and 6,7-³H-phylloquinone in order to determine biological activity and possible differences in turnover, localization and metabolism of the cis vitamin in deficient rats. Intracardial injection of 5 µg of the tritiated cis preparation gave a prothrombin response resembling that obtained from 0.5 µg of synthetic vitamin (80% trans), thus indicating that the cis vitamin had little or no biological activity. The turnover of ³H in several tissues was similar to that observed after the injection of unfractionated ³H-phylloquinone (80% trans). Despite the low biological activity of the cis preparation, the distribution of ³H in liver subcellular fractions was also similar to that previously observed with unfractionated ³H-phylloquinone. These results are taken as evidence that most of the administered phylloquinone in liver is not bound to the active site of the vitamin. In all cases studied, the proportion of ³H in cis and trans phylloquinone recovered from the tissue was similar to that in the administered vitamin.

KEY WORDS: • vitamin K • phylloquinone • cis/trans isomers • prothrombin • liver • subcellular fractionation • metabolism

¹ Supported in part by the Rhode Island Heart Association and grants AM 11311 and AM 09909 from the National Institutes of Health. In this paper the nomenclature of vitamin K is that recommended by the IUPAC-IUB Nomenclature Commission (Biochem. J. 102: 15, 1967). Vitamin K₁ is called phylloquinone. The trivial names, phylloquinone and menaquinone are equivalent to phytylamenaquinone and prenylmenaquinone recommended by the IUNS Committee on Nomenclature (J. Nutr. 101: 133, 1971).

² Present address: Department of Biochemistry, University of Nebraska College of Medicine, Omaha, Nebraska 68105.

Manuscript received 20 December 1971.