Hydraulic pressure stimulates adenosine 3 ',5 '-cyclic monophosphate accumulation in endothelial cells from Schlemm's canal

PURPOSE. Fluid flow across various endothelia results in a variety of intra cellular and extracellular adaptations. In the living eye, aqueous humor fl ows across the surface of endothelial cells on trabecular meshwork (TM) bea ms and in the juxtacanalicular tissue and through or between a continuous m onolayer of endothelial cells that line Schlemm's canal (SC). This study wa s undertaken to test the hypothesis that fluid flow induces biochemical cha nges in the endothelial cells of the outflow pathway that may modify outflo w resistance. METHODS. Trabecular meshwork and SC cells isolated from the outflow pathway of human cadaveric eyes were seeded onto porous filters, placed in Ussing- type chambers, and subjected to fluid flow driven by a pressure head of 15 mm Hg on their apical surface. Cell lysates were prepared and analyzed for adenosine 3',5'-cyclic monophosphate (cAMP) accumulation. Barrier function of cell monolayers was examined using transendothelial electrical resistanc e measurements. RESULTS. Three different SC cell strains in 14 independent experiments resp onded with at least a threefold increase in cAMP that was both time and pre ssure dependent. Conversely, flow-treated TM cells failed to respond in six independent experiments in which five different TM cell strains were used. Electrical resistance across cell monolayers positively correlated with cA MP accumulation and was calcium sensitive. CONCLUSIONs. cAMP signaling is affected by pressure differentials across SC cell monolayers and provides evidence for the participation of SC cells in the regulation of aqueous outflow.