[In vitro effect of citrate and phosphates on calcium transport in the rat ileum].

OBJECTIVES AND METHODS

The effect of the presence of phosphates or citrate on ileal calcium (Ca) absorption was studied by using rat ileum mounted in a Ussing chamber.

RESULTS

Mucosa-to-serosa and serosa-to-mucosa undirectional fluxes were not modified by mucosal addition of 2.8 mM Na phosphate or 2.0 mM Na citrate to Krebs-Ringer-bicarbonate buffer containing 1.25 mM CaCl2. However, 50 mM Na citrate induced a significant and similar increase of both unidirectional Ca fluxes, leading to no modification of net Ca flux. This high citrate concentration was associated with a significant increase of tissue conductance and no alteration of zona adherens and tight junction as observed by electron microscopy.

CONCLUSIONS

Thus in the absence of any Ca gradient along the epithelium, even at high concentration, citrate did not induced modification of ileal Ca absorption.