Electrical parameters and water permeability properties in monolayers formed by epithelial cells cultured on permeable supports

MARCELO OZU; MARIO PARISI; ROXANA TORIANO

Río de Janeiro

Congreso; V Congreso Iberoamericano de Biofísica; 2003

Sociedad de Biofísica Latinoamericana (SOBLA), Sociedad de Biofísica de España (SBE), Sociedad Brasilera de Biofísica (SBBF)

T84, Caco-2, LLC-PK1 and RCCD-1 are established cell lines, originated in intestinal and renal epithelia, whose permeability properties have been widely explored. Now the osmotic permeability (POSM), hydraulic permeability (PHYDR) and transport associated net water fluxes (JW-transp), together with short circuit current (ISC), transepithelial resistance (RT) and potential difference were measured in T84 monolayers and compared with those previously reported in Caco-2, LLC-PK1 and RCCD-1 cells. In native cells (non expressing aquaporins) it was observed that: 1) Osmotic (JW-osm) and hydrostatic fluxes (JW-hydr) increased linearly with applied gradients. 2) Correlation between POSM and RT adjust for a first order exponential curve 3) No clear association between PHYDR and RT could be demonstrated: High PHYDR values could be observed in a tight epithelia, confirming that a "water leaky" barrier is not necessarily an "electrically leaky" one 4) The important increase in ISC induced by DCEBIO (a "net Cl-secretor agent") in T84 cells was associated to a modest secretor JW-transp. This was at variance with previous results observed in RCCD-1 cells stimulated with vasopressin (absorptive fluxes) or in T84 cells secreting water under the action of Escherichia coli Heat Stable Enterotoxin (STa). It is concluded that while the presence of aquaporins is necessary to dissipate an external osmotic gradient in "water-tight" epithelial barriers, coupling between water and ions transports could no be explained by a simple and common underlying mechanism.