RESUMO
To determine the effects of cadmium on the intestinal absorption of calcium, everted gut sacs from rats orally dosed with 0, 0.05, 0.5 or 5.0 mg Cd daily for 3 weeks were placed in media containing 4 x 10(-5) M Ca. Tissue content of calcium after 1 hour incubation was approximately 1.5 times greater for the 5-mg Cd dose. Serosal fluid content of calcium was decreased by the 0.5- and 5-mg Cd/day doses. In other experiments, gut sacs were incubated in bathing media containing 4 x 10(-5) Ca and Cd in concentrations of 10(-4) to 10(-2) M. Tissue and serosal fluid uptake of calcium decreased as Cd concentration increased. To determine the effects of cadmium on the accumulation of calcium against a concentration gradient, equimolar concentrations of Cd were placed in the mucosal and serosal fluids. Cadmium was added to the mucosal fluid. The accumulation of calcium was abolished by 1.5 x 10(-4) M Cd while at 10(-6) M Cd the accumulation was decreased to one-third the control value. The results indicate that acute or chronic exposure of the intestine to cadmium decreases the intestinal absorption of calcium.
Assuntos
Cádmio/farmacologia , Cálcio/metabolismo , Absorção Intestinal/efeitos dos fármacos , Animais , Relação Dose-Resposta a Droga , Técnicas In Vitro , Cinética , Masculino , RatosRESUMO
The purpose of this study was to measure intestinal absorption and retention of cadmium in the newborn pig and to compare data from the pig, rat and guinea pig, three species that differ greatly in their ability to absorb macromolecules at birth. Newborn pigs were administered a single oral dose of 50 muCi of 115mCd (0.20 mCi/mg Cd) 24 hours after birth and killed at intervals between 1 and 14 days after dosing. Cd absorption and gastrointestinal retention were then determined; these data were compared with similar data from the rat and guinea pig. The cumulative Cd absorption was about 4.0, 5.0 amd 23% of the dose in the day-old pig, rat and guinea pig, respectively. The residence time of Cd in the intestinal tract was longer in the rat than in the pig or guinea pig, the 50% excretrion time being 15, 8, and 5 days in the rat, pig and guinea pig, respectively. Cd absorption in the neonate appears to be a two-step process: mucosal uptake of Cd from the lumen, probably by pinocytosis, followed by transfer of a portion of this Cd into the body. This transfer process is similar, but does not entirely coincide with changes associated with protein absorption in the neonate.
