CONICET | Buscador de Institutos y Recursos Humanos

p { margin-bottom: 0.21cm; } The association of IAP with Ca absorption is partially known. Previous experiments indicated that a binds to IAP, contributes to maintain the active structure and increases the activity of membrane-bound form. There is evidence that the decrease in pH alter the TRPV6-Ca channel activity. The aim of this study was to evaluate the effect of pH and phosphate generated by the action of the IAP on Ca absorption. Experiments were carried out with everted duodenal sacs. The intestinal mucosa was exposed to a buffer with Ca 1, 10, 50 or 100 mM, pH 9 and the serosa to the same solution without Ca (n=4/group). Phosphorus (P), Ca and pH were measured in the mucosa solution at 0, 10 and 20 min. Ca absorption was calculated by the difference between Ca concentration at 0 and 20 min. The precipitation of Ca phosphate was calculated with pH, P and Ca. Experiments were also carried out in presence of phenylalanine (Phe), an inhibitor of the IAP. As Ca increased in the solution, there was a significant decrease in Ca absorption (Ca 1: 45±4; Ca 10: 42±11; Ca 50: 38±11; Ca 100: 30±11) and a significant decrease of pH (Ca 1: 7.8±0.1; Ca 10: 7.4±0.1; Ca 50: 6.9±0.2; Ca 100: 6.9±0.1). Precipitation as Ca phosphate was negligible, and it was not responsible of the decrease in Ca absorption. When the experiments were carried out in the presence of Phe there was an increase in Ca absorption (Ca 1: 53±5; Ca 10: 56±6; Ca 50: 42±10; Ca 100: 40±6) with a decrease in pH not as evident as in the absenced of Phe (Ca 1: 8.33±0.15; Ca 10: 8.05±0.18; Ca 50: 8.17±0.17; Ca 100: 8.28±0.21). These results support the hypothesis that pH regulates the entry of Ca to the enterocyte and acts as a sensor of luminal Ca.

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