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 insulin in ascorbic acid transport has been reported. Therefore, the effects of Cr and ascorbate depletion on tissue ascorbic acid and C-14 distribution and excretion after a C-14 ascorbate dose were investigated in guinea pigs. As utilization of dietary Cr is affected by interaction with other minerals, tissue manganese (Mn), zinc (Zn), copper (Cu), and iron (Fe) were examined. For 20 wk, 40 weanling animals were fed either 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 ascorbate/d (-C) or 10 mg ascorbate/d (+C) for 20 wk. Animals fed the Cr-depleted diet had decreased weight at 20 wk (p < 0.01). Six hours before necropsy, animals were dosed by micropipette with 1.8 mu Ci of L-[carboxyl-C-14] ascorbic acid and placed in metabolic cages. Ascorbate supplementation increased Fe concentrations in most analyzed tissues, hepatic C-14, tissue ascorbate and Mn concentration in the adrenal and testes; but decreased the concentrations of Cu in the kidney and Mn in the spleen. Liver Mn concentration was higher and kidney Mn concentration was lower in +Cr animals. Interactions between Cr and ascorbic acid affected Mn concentrations in bone and brain. These results indicate that ascorbate and Cr may affect Mn distribution. Chromium supplementation decreased plasma cortisol, brain C-14 and the amount of C-14 expired as carbon dioxide. These findings suggest that dietary Cr may affect ascorbic acid metabolism and the metabolic response to stress.