Water and Solute Coupling in a Model of Intestinal Secretion: T84 Cells

ROXANA TORIANO; MARCELO OZU; MARIO PARISI

Buenos Aires

Congreso; XIV International Biophysics Congress; 2002

International Union for Pure and Applied Biophysics (IUPAB) y Sociedad Argentina de Biofísica (SAB)

T84 cells cultured on permeable support are a good model to study transepithelial water movements. It was generally accepted that water secretion in T84 cells is passively and isotonically associated to Cl secretion, although water transfers were not measured. In a recent work (Toriano et al., Am J Physiol 2001, 281:816-22) we shown that this could be not always true. For instance an spontaneous secretor flux was observed in the absence of Cl secretion while the net Cl exit induced by STa can not explain, if isotonic conditions are accepted, the measured associated net water flux (Jw). RT-PCR experiments indicated that aquaporins would be not expressed in T84 cells. The observed Jw can move between or through the cells. In this last case, water could go through the lipid bilayer, through membrane aquaporins or, as recently proposed, cotransported with different solutes. Is not easy to understand all our results just assuming water movement across the lipid bilayer following an external osmotic gradient generated by the salt transport. We propose an alternative model in which an ionic pair is transported into a molecular cavity generating inside it an osmotic gradient. Secondly, this gradient would be dissipated through an associate aquaporin-like channel. We are actually exploring the role of HCO3- on water secretion, and the water pathway in osmotically induced transepithelial fluid movements.