ZINC-METABOLISM IN RATS - EFFECTS OF INTESTINAL RESECTION, CHOLECALCIFEROL AND ASCORBIC-ACID

The metabolic balance technique was used to study the effect of dietary composition on zinc nutritive utilization in rats in which 50% of the distal small intestine (DSI) was removed, and in transected rats (controls). Six experiments with three different diets were done: the basal diet contained 12% protein (casein + 5% D,L-methionine) and 4% lipid (medium chain triglycerides (MCT), olive oil and sunflower oil in equal parts); the other two diets were obtained by supplementing the basal diet with cholecalciferol (0.4 mg/kg diet) or adding ascorbic acid (150 mg/kg diet). Resection of 50% of the DSI markedly affected the digestive and metabolic utilization of zinc [apparent digestibility coefficient (ADC), and zinc balance] in rats fed on the basal diet alone or additioned with vitamin C. However, these parameters were not so markedly affected by the surgery in rats whose diet was supplemented with cholecalciferol. To investigate postresection zinc homeostasis we also measured the concentrations of this metal in blood, plasma and several organs (liver, femur, sternum, longissimus dorsi (LD) muscle and testes) one month after surgery. We found no alterations in the distribution of zinc in the organism under any of the experimental conditions. We conclude that the adaptive mechanisms that maintaining trace metal homeostasis are operative one month after intestinal resection.