Induction of endothelial-cell permeability by extracellular nucleic acids. (A) Following addition of different concentrations of RNA, poly-I:C, DNA, or ssRNA to BMEC monolayers for 3 hours as indicated, permeability changes were quantitated by measuring the flux of [³H]inulin.²⁹  (B) Permeability changes were analyzed in nontreated cells (control) or cells treated with RNA (50 μg/mL), poly-I:C (25 μg/mL), or ssRNA (0.25 μg/mL) as indicated in the absence (−) or presence of RNase or following addition of nucleotide monophosphates (NMPs; 50 μg/mL) instead of nucleic acids. (C) Permeability changes were measured after incubation of cells with RNA, as compared with control cultures (control) as indicated, in the absence ([minus) or presence of RNase inhibitor. Control flux determined after 3 hours was set to 100%, and values represent the mean (± SEM; n = 24) for each condition. *P < .05 compared with untreated cells.