TISSUE SPECIFIC-DISTRIBUTION AND METABOLISM OF VITAMIN-A ARE AFFECTEDBY DIETARY-PROTEIN LEVELS IN RATS

The effect of dietary protein levels on tissue-specific distribution a nd metabolism of vitamin A was studied in rats given [15-C-14] retinol (C-14-ROH). The weanling rats were fed a low level vitamin A diet for 10 days, then rats (15 rats per group) were divided into 2 groups, on e was given a 40% casein diet as a high protein diet (HP-diet), and th e other a 5% casein diet as a low protein diet (LP-diet), After 10 day s feeding on these diets,C- 14-ROH(5 mu Ci/rat) was given to both grou ps, HP-diet and LP-diet, by intraperitoneal injection. The radioactivi ty in the exhalated gases, urine and feces was measured to estimate th e rate of vitamin A metabolism, The tissue specific-distribution of RO H was studied in terms of the radioactivities of the ROH fractions sep arated by HPLC, The hepatic C-14-ROH content in the HP-diet group was lower than that in the LP-diet group at 24, 48, and 72 hours after adm inistration of C-14-ROH, In contrast, C-14-ROH content in serum, splee n, pancreas, and small intestinal mucosa in the HP-diet group was high er than that in the LP-diet group, The radioactivity of the exhalated gas and feces was higher in the HP-diet group. These results suggest t hat metabolism of vitamin A is higher with intake of a HP-diet, Thus, dietary protein levels may affect tissue-specific distribution and met abolism of vitamin A, thereby modulating the actions of this vitamin.