Metabolism and Vitamin K Activity of cis Phylloquinone in Rats

Abstract

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.