Role of vascular nitric oxide synthase in endotoxin shock of Propionibacterium acnes-sensitized rats

Effect of nitric oxide on the ligand-binding activity of albumin

The redox state of the Cys-34 on albumin plays an important role in ligand binding of this plasma protein. We previously reported that mixed-disulfide formation of albumin with low molecular weight thiols, such as cysteine and glutathione, increased the affinity of this protein for phenolsulfophthalein (PSP) and Cu(II). Although nitric oxide (NO) and its metabolites easily react with various thiols, including that of albumin, and form S-nitrosothiol derivatives, the effect of such modification on the ligand-binding activity of this plasma protein remains to be elucidated. Kinetic analysis revealed that S-nitrosylation of Cys-34 on bovine serum albumin (BSA) decreased its binding activity for PSP. NO also decreased the ligand-binding activity of fresh plasma samples from rat and human. S-nitrosylation also decreased the binding activity of BSA for Cu(II). These results indicate that reversible modification of the Cys-34 by NO and oxidative stress might play regulatory roles in the binding and transport of organic anions and heavy metals in the circulation.

Nitric oxide stimulates prostaglandin synthesis in cultured rabbit gastric cells

Both prostaglandins (PGs) and nitric oxide (NO) have cytoprotective and hyperemic effects in the stomach. However, the effect of NO on PG synthesis in gastric mucosal cells is unclear. We examined whether sodium nitroprusside (SNP), a releaser of NO, stimulates PG synthesis in cultured rabbit gastric mucus-producing cells. These cells did not release NO themselves. Co-incubation with SNP (2 x 10(-4), 5 x 10(-4), 10(-3) M) increased PGE2 synthesis, and SNP (10(-3) M) increased PGI2 synthesis in these cells. Hemoglobin, a scavenger of NO, (10(-5) M) eliminated the increase in PGE2 synthesis by SNP, but methylene blue, an inhibitor of soluble guanylate cyclase, (5 x 10(-5) M) did not affect the increase in PGE2 synthesis by SNP. 8-bromo guanosine 3':5'-cyclic monophosphate (8-bromo cGMP), a cGMP analogue, (10(-6), 10(-5), 10(-4), 10(-3) M) did not affect PGE2 synthesis. These findings suggest that NO increased PGE2 and PGI2 synthesis via a cGMP-independent pathway in cultured rabbit gastric cells.