NITRIC-OXIDE DILATES TIGHT JUNCTIONS AND DEPLETES ATP IN CULTURED CACO-2BBE INTESTINAL EPITHELIAL MONOLAYERS

We tested the hypothesis that nitric oxide (NO) modulates the permeabi lity of tight junctions in a model intestinal epithelium (Caco-2BBe mo nolayers). Incubation with sodium nitroprusside (SNP) resulted in time - and concentration-dependent decreases in transepithelial resistance. Permeability to fluorescein sulfonic acid increased during incubation for 24 h in the presence of 1.25 mM SNP, 5 mM S-nitroso-N-acetylpenic illamine (SNAP), or 1% NO gas. SNP-induced hyperpermeability was not d ue to loss of cell viability, as confirmed by intact ultrastructure, u naltered lactate dehydrogenase release, and ability to recover baselin e permeability. Incubation with SNP increased permeability but only mi nimally increased intracellular levels of guanosine 3',5'-cyclic monop hosphate (cGMP). Incubation with Escherichia coli heat-stable enteroto xin greatly increased cGMP levels with only a minimal effect on permea bility. Cellular ATP levels decreased after incubation with SNP, SNAP, or gaseous NO. Incubation with SNP led to diminished fluorescein-phal loidin staining of junctional actin (confocal microscopy) and widened tight junctions (electron microscopy). We conclude that NO reduces ATP levels and reversibly increases the permeability of tight junctions i n cultured Caco-2BBe cells.