Liver vitamin A levels in rats are predicted by a modified isotope dilution technique.
We tested the hypothesis that the fraction of an injected dose (FDp) of [3H]retinol remaining in plasma could be used to predict liver vitamin A mass. Rats (n = 36) with liver vitamin A ranging from 1.4 to 23,000 nmol received an intravenous dose of [3H]retinol-labeled plasma. Plasma samples obtained at 4, 4.4, 5, 5.4, 6, 7 and 8 d were analyzed for radioactivity; liver vitamin A levels were determined at 8 d. Using a regression equation developed previously [liver vitamin A (nmol) = 7493.exp(-148.FDp)], there was a log linear relationship between FDp and liver vitamin A mass from 1.4 to 5200 nmol retinol; the equation did not predict levels > or = 7500 nmol. By expanding the regression equation [liver vitamin A (nmol) = 88,928.exp(-1347.FDp) + 5606.exp(-120.FDp)] and using the FDp at 4.4 d, liver vitamin A levels ranging from < 4 to 23,000 nmol were well predicted. Satisfactory equations were also developed for data obtained at 4, 5 and 5.4 d. We conclude that this modified isotope dilution technique is a sensitive and reliable method for assessing vitamin A status in rats over a wide range of vitamin A nutriture. It is likely that this method could be modified for use in humans.
Duncan
T E
TE
Nutrition Department, Pennsylvania State University, University Park 16802.
Green
J B
JB
Green
M H
MH
D000818:Animals; D008099:Liver / Q000737:chemistry*; D008297:Male; D010949:Plasma / Q000737:chemistry; D011237:Predictive Value of Tests; D011865:Radioisotope Dilution Technique; D051381:Rats; D017207:Rats, Sprague-Dawley; D012044:Regression Analysis; D014316:Tritium; D014801:Vitamin A / Q000032:analysis* / Q000097:blood
D014316:Tritium; D014801:Vitamin A