RESUMO
Rats weighing 100 ñ 8 g were used in an in vivo kinetic study of the intestinal absorption of calcium (CaA) from there systems: 1) CaCl2, 2) whole cow's milk (M), and 3) a taple Brazilian diet (SBD). Food substrates were treated with HCl, neutralized and diluted with 0.15 mM NaCl to different concentrations. Each dilution was assayed by introducing 2 ml into the small intestine and the final amount of Ca*+ in the small intestine was determined 30 min later. The values for velocity (v= Vmax (Ca*+ in the small intestine was determined 30 min later. The values for velocity (v+Vmax (Ca*+)/(Ca*+) + Km) and affinity (1/Km) for the food substrates were 1.35, 15.51 and 2.31 *g Ca*+/min and 0.29, 0,016 and 0.266 *g Ca*+/ml, respectively. We conclude that the higher affinities observed for CaCl2 and SBD were not correlated with velocity. Factors modifying CaA appear to be protein (stimulator) and phylate and fiber (inhibitors)