METABOLIC ACTIVITIES OF VITAMIN A AND RELATED COMPOUNDS IN ANIMALS

1. Activity tests of various dispersoids on the intestinal movement, using isolated segments of the small intestine of the rat under well-controlled experimental conditions, demonstrated that free vitamin A alcohol showed excellent activity on the intestinal movement, but the acetate was always inactive. In the case of vitamin A palmitate, the diminished excursion was observed at the initial stage, while the excursion recovered to normal after a few minutes. It seems to be possible that the results are due to the presence of vitamin A palmitate-esterase.2. Vitamin A aldehyde induced a little larger excursion, whereas vitamin A acid was completely inhibitive. Vitamin A alcohol-vitamin A acid-ester showed a diminished excursion at the initial stage, but after a few minutes increased rate of the intestinal movement was seen.3. Natural vitamin A alcohol concentrate always indicated excellent action on the rat intestinal movement.4. No activity was observed with β-carotene, whereas vitamin A alcohol derived from β-carotene by incubation with fresh rat intestinal tissue for 90 minutes always indicated active results.5. These findings seem to suggest that free vitamin A alcohol may be linked to the intermediate source of hydrogen transfer for the muscular work in the intestinal tissue.