Asymmetry in osmotic response of cortical collecting duct cells: Role of Aquaporin-2

O. CHARA; P. FORD; V . RIVAROLA; M . PARISI; C . CAPURRO

JOURNAL OF MEMBRANE BIOLOGY

Springer Science

Lugar: New York, USA; Año: 2005 vol. 207 p. 143 - 150

0022-2631

Transition from antidiuresis to diuresis exposes cortical collecting duct cells (CCD) to asymmetrical changes in environment osmolality inducing an osmotic stress which activates numerous membrane-associated events. The aim of the present work was to investigate, either in the presence or not of AQP2, the transepithelial osmotic water permeability (Posm) following cells exposition to asymmetrical hyper or hypotonic gradients. For this purpose transepithelial net volume fluxes were recorded every minute in two CCD cell lines: one not expressing AQPs (WT-RCCD1) and other stably transfected with AQP2 (AQP2-RCCD1). Our results demonstrated that the rate of osmosis produced by a given hypotonic shock depends on the gradient direction (osmotic rectification) only in the presence of apical AQP2. In contrast, hypertonic shocks elicit Posm rectification, independently of AQP2 expression, and this phenomenon would be linked to modulation of basolateral membrane permeability. No asymmetry in transepithelial resistance was observed, under hypo or hypertonicity, indicating that rectification can not be attributed to a shunt through the tight junction path. We conclude that osmotic rectification may be explained in terms of dynamical changes in membrane permeability probably due to activation/incorporation of AQPs or transporters to the plasma membrane via some mechanism triggered by osmolality.