[In vitro effect of citrate and phosphates on calcium transport in the rat ileum]
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1EPHE, Laboratoire de Physiologie, Faculté de Pharmacie, Chatenay-Malabry.
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.