After an appropriate dose of 3,4-didehydroretinol (vitamin A2, DR) is given orally in corn oil to retinol (R)-depleted rats, the ratio of plasma DR/R values at 3.5 h is inversely related to the liver concentration of vitamin A (Tanumihardjo and Olson, 1988). In the present study, a similar procedure, termed the modified relative dose response (MRDR) assay, was employed with rats containing a much broader range of liver reserves; ie, < 2 to 107 nmol of vitamin A per g wet weight of liver (< 1 to 30 μg/g). The DR/R ratio for 15 of 16 rats with liver reserves < 17 nmol/g (< 5 μg/g) was > 0.15, whereas the ratio was < 0.15 for 7 of 8 rats with liver reserves > 17 nmol/g. This distribution provides sensitivity, specificity and positive predictive values of 94, 88 and 94 per cent, respectively. The DR/R ratios reached a maximal plateau in two other groups of rats between 3.5 and 8 h. At all times up to 24 h, mean DR/R ratios for vitamin A-depleted rats (45 ± 6 nmoles of vitamin A/g liver) were approximately twice those for vitamin A-sufficient rats (230 ± 40 nmoles of vitamin A/g liver). In three well-nourished adults, presumably with liver reserves of > 300 nmol/g wet weight liver (> 80 μg retinol equivalents/g), and in two young (1- and 3-years old) well-nourished children, maximal DR/R ratios were < 0.023). In these cases, peak DR/R ratios were observed, with one possible exception, between 8 and 12 h. Thus, the MRDR assay, which is a useful indicator of marginal vitamin A status in rats, seems also applicable to humans.
|Original language||English (US)|
|Number of pages||6|
|Journal||European Journal of Clinical Nutrition|
|State||Published - 1990|
ASJC Scopus subject areas
- Medicine (miscellaneous)
- Nutrition and Dietetics