A kinetic study of some factors which influence the intestinal absorption of calcium in rats.
Rats weighing 100 +/- 8 g were used in an in vivo kinetic study of the intestinal absorption of calcium (CaA) from three systems: 1) CaCl2, 2) whole cow's milk (M), and 3) a staple 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 Ca2+ in the small intestine was determined 30 min later. The values for velocity (v = Vmax (Ca2+)/(Ca2+) + Km) and affinity (1/Km) for the food substrates were 1.35, 15.51 and 2.31 micrograms Ca2+/min and 0.29, 0.016 and 0.266 micrograms Ca2+/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 phytate and fiber (inhibitors).
de-Angelis
R C
RC
Departamento de Fisiologia e Biofísica, Universidade de São Paulo, Brasil.
Oguido
A K
AK
D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics*; D002122:Calcium Chloride / Q000494:pharmacology; D004032:Diet; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D008892:Milk; D051381:Rats
D002122:Calcium Chloride; D002118:Calcium