Rote of AQP2 in TRPV4 modulation: implications in cell volume regulation

LUCIANO GALICIA; PILAR FLAMENCO; VALERIA RIVAROLA; CLAUDIA CAPURRO; PAULA FORD

PUCON, CHILE

Congreso; XXIII Congresos de la Asociación Latinoamericana de Ciencias Fisiológicas (ALACF),; 2009

Cell volume regulation is particularly important for kidney cells. When cells are exposed to hypotonic extracellular fluid, they first swell and then start to recover their original volume through a process called regulatory volume decrease (RVD). Using a fluorescent probe technique, we have studied cell volume changes and intracellular calcium in response to a hypotonic shock in two renal cell lines, one not expressing aquaporins (WT-RCCD1) and another displaying a constitutive expression of AQP2 (AQP2-RCCD1). We have previously reported, in these cell lines, that AQP2 is critical to produce an intracellular calcium increase, necessary to activate RVD. Here, we examined the involvement of the cation channel transient receptor potential vanilloid 4 in the hypotonic response. We have found, in AQP2-RCCD1 cells, that the hypotonicity induced [Ca2+]i increases and the subsequent RVD  are both inhibited by ruthenium red, a TRPV4 inhibitor. Immunofluorescence studies show that under isotonic conditions TRPV4 is distributed mainly in intracellular compartment in both cell lines. However under hypotonic conditions TRPV4 is translocated to the cell membrane only in AQP2-RCCD1 cells. Taken together, our data suggest a functional interaction between TRPV4 and AQP2 in sensing hypotonicity.