VITAMIN ACTIVITIES IN HUMAN PORTAL, HEPATIC AND FEMORAL BLOOD AFTER VITAMIN INGESTION

The dynamics of intestinal absorption, blood concentration and distrib ution of thiamin, biotin, nicotinate, riboflavin, pantothenate, variou s folates (folic acid, folinic acid, pteroyltriglutamate), vitamins A, E, C, B-12, and B-6 were monitored in 12 patients by multiple simulta neous sampling of brood obtained by combined catheterization of portal vein, hepatic vein, and femoral artery after vitamin ingestion. All w ater-soluble vitamins proved elevated after vitamin ingestion principa lly in portal blood within 10 minutes as compared with hepatic and fem oral blood. Elevated vitamin levels in portal blood - compared to hepa tic and femoral blood - remained high even after 120 min. indicating t hat absorption from the gut was still progressing. In contrast, ingest ion of the fat-soluble vitamins A and E evoked no elevated vitamin act ivity in portal blood. Within 10 min. after vitamin ingestion, all fol ates were converted into reduced and methylated 5-methyltetrahydrofola te (5-CN3THF) on passage through the gut. At this time, portal blood e levation of 5-CH3THF persisted before its elevation in hepatic or femo ral blood. Presumably, the elevation was not due to the flushing of st ored 5-CH5THF from tissues but rather of folate conversion to 5-CH3THF upon gut passage. The significance of these findings is discussed.