CHROMIUM AND CHRONIC ASCORBIC-ACID DEPLETION EFFECTS ON TISSUE ASCORBATE, MANGANESE, AND C-14 RETENTION FROM C-14 ASCORBATE IN GUINEA-PIGS

Chromium (Cr) potentiates the effects of insulin and a role for insuli n in ascorbic acid transport has been reported. Therefore, the effects of Cr and ascorbate depletion on tissue ascorbic acid and C-14 distri bution and excretion after a C-14 ascorbate dose were investigated in guinea pigs. As utilization of dietary Cr is affected by interaction w ith other minerals, tissue manganese (Mn), zinc (Zn), copper (Cu), and iron (Fe) were examined. For 20 wk, 40 weanling animals were fed eith er a Cr-deficient (<0.06 mu g Cr/g diet, -Cr) or a Cr-adequate (2 mu g Cr from CrCl3/g diet, +Cr) casein-based diet and were given 1 mg asco rbate/d (-C) or 10 mg ascorbate/d (+C) for 20 wk. Animals fed the Cr-d epleted diet had decreased weight at 20 wk (p < 0.01). Six hours befor e necropsy, animals were dosed by micropipette with 1.8 mu Ci of L-[ca rboxyl-C-14] ascorbic acid and placed in metabolic cages. Ascorbate su pplementation increased Fe concentrations in most analyzed tissues, he patic C-14, tissue ascorbate and Mn concentration in the adrenal and t estes; but decreased the concentrations of Cu in the kidney and Mn in the spleen. Liver Mn concentration was higher and kidney Mn concentrat ion was lower in +Cr animals. Interactions between Cr and ascorbic aci d affected Mn concentrations in bone and brain. These results indicate that ascorbate and Cr may affect Mn distribution. Chromium supplement ation decreased plasma cortisol, brain C-14 and the amount of C-14 exp ired as carbon dioxide. These findings suggest that dietary Cr may aff ect ascorbic acid metabolism and the metabolic response to stress.