Vasopressin regulates water flow in a rat cortical collecting duct cell line not containing known aquaporins

Transepithelial water movements and arginine-vasopressin (AVP)-associated o nes were studied in a renal cell line established from a rat cortical colle cting duct (RCCD1). Transepithelial net water fluxes (J(W)) were recorded e very minute in RCCD1 monolayers cultured on permeable supports. Spontaneous net water secretion was observed, which was inhibited by serosal bumetanid e (10(-5) M), apical glibenclamide (10(-4) M) and apical BaCl2 (5 x 10(-3) M). RT-PCR, RNAse protection and/or immunoblotting experiments demonstrated that known renal aquaporins (AQP1, AQP2, AQP3, AQP4, AQP6 and AQP7) were n ot expressed in RCCD1 cells. AVP stimulates cAMP production and sodium reab sorption in RCCD1 cells. We have now observed that AVP significantly reduce s the spontaneous water secretory flux. The amiloride-sensitive AVP-induced increase in short-circuit current (I-sc) was paralleled by a simultaneous modification of the observed J(W): both responses had similar time courses and half-times (about 4 min). On the other hand, AVP did not modify the osm otically driven J(W) induced by serosal hypertonicity. We can conclude that : (i) transepithelial J(W) occurs in RCCD1 cells in the absence of known re nal aquaporins; (ii) the "water secretory component" observed could be link ed to Cl- and K+ secretion; (iii) the natriferic response to AVP, preserved in RCCD1 cells, was associated with a change in net water flux, which was even observed in absence of AQP2, AQP3 or AQP4 and (iv) the hydro-osmotic r esponse to AVP was completely lost.