['Nitric oxide (NO) is known as a regulator of inflammation and immunity. The purpose of this study was to investigate the influence of this signal molecule on the rat immunoglobulin A (IgA) system using Nomega-nitro-L-arginine-methyl ester (L-NAME), which inhibits the activity of all isoforms of NO synthase.', "The experiments were performed on adult female Wistar rats showing diestrus day 1 that were treated with L-NAME (30 or 50 mg/kg, s.c.). Untreated and saline-injected animals were used as controls. The rats were sacrificed 3 h following L-NAME or saline administration. The concentration of IgA in serum and intestinal extracts was determined by a sandwich enzyme-linked immunosorbent assay. The number of IgA-expressing cells per area unit of Peyer's patches and the intestinal lamina propria was evaluated using stereological analysis.", 'The results showed that L-NAME decreased the level of IgA in serum and elevated its concentration in intestinal extracts. Additionally, the increased number of IgA+ cells was found in the intestinal lamina propria in both experimental groups.'] Does blockade of nitric oxide synthesis modulate rat immunoglobulin A?