Extra-Hepatic Vitamin A Concentrations in Captive Rhesus (Macaca Mulatta) and Marmoset (Callithrix Jacchus) Monkeys Fed Excess Vitamin A

Recent work examining vitamin A (VA) status of rhesus monkeys (Macaca mulatta) used as models for human biomedical research has revealed subtoxic hepatic VA concentrations. Livers of marmoset monkeys (Callithrix jacchus), another experimental animal, were also high in VA as was serum retinyl ester concentration. Both species consumed common research diets that provided up to four times the amount of VA (retinyl acetate) as currently recommended by the National Research Council. To further define the effects of chronically high dietary VA as found in many human subpopulations, we analyzed lung and kidney tissues from subtoxic rhesus and marmoset monkeys (n = 10 each) for retinol and retinyl esters. Marmoset kidneys contained 0.88 ± 0.66 mumol VA/g and was nearly the same as hepatic VA at 1.40 ± 0.44 mumol/g (p = 0.143). In contrast, rhesus kidney VA concentrations were 0.0100 ± 0.0032 mumol/g, even though liver reserves were 18.8 ± 6.4 mumol VA/g (p < 0.0001). Lung tissue VA concentrations, 0.0022 ± 0.0012 and 0.0061 ± 0.0025 mumol/g for marmosets and rhesus, respectively, were lower as compared with kidney (p < 0.011). Kidney and lung VA in monkeys with adequate, but not excessive, VA stores have not been determined; hence, interpretation of these findings is limited to tissue retinol and retinyl ester profiles and extrapolation from other species rather than direct comparison to "normal" values.