The Mongolian Gerbil (Meriones unguiculatus) Is an Appropriate Animal Model for Evaluation of the Conversion of β-Carotene to Vitamin A

Vitamin A (VA) deficiency is the leading cause of blindness in children in developing countries. Dietary intervention with foods rich in provitamin A carotenoids, such as β-carotene (βC), has been suggested as one solution to this problem. The objective of the two studies described in this paper was to examine the utilization of βC as a source of VA at different stages of VA depletion using the Mongolian gerbil as a model. Male 4- to 5-wk-old Mongolian gerbils were fed powdered βC-free semipurified diets either with or without VA for 26 d (Study 1), or without VA for 8-10 wk (Study 2). Gerbils were then fed diets with or without VA (20.9 nmol/g diet) and/or βC [(67.0 μmol/g diet (Study 1) and 145.9 μmol/g diet (Study 2)] for variable periods. Two (Study 1) or three (Study 2) days before termination of the study, 3-4 gerbils per group were dosed orally with 14 C-βC. Tissues were evaluated for VA and βC content by HPLC. Liver was extracted with and without saponification to evaluate 14 C-βC and 14 C-VA content. The results demonstrate the following: 1) the gerbil is an appropriate animal model to study βC utilization; 2) 20.9 nmol VA/g diet is more than sufficient for this species; 3) the daily VA utilization rate for this species is calculated to be 3.1 μg/100 g body weight; 4) a highly bioavailable source of βC at a 6:1 weight ratio of βC:VA is sufficient to reverse marginal VA status in this model; and 5) a highly bioavailable source of βC fed between a 6:1 and 13:1 weight ratio to VA provides equivalent VA status as preformed VA in Mongolian gerbils.