T. Furusho et al., TISSUE SPECIFIC-DISTRIBUTION AND METABOLISM OF VITAMIN-A ARE AFFECTEDBY DIETARY-PROTEIN LEVELS IN RATS, International journal for vitamin and nutrition research, 68(5), 1998, pp. 287-292
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.