Effect of NG-monomethyl L-arginine (L-NMMA) and NG-nitro L-arginine (L-NOARG) on non-adrenergic non-cholinergic relaxation in the circular muscle of the human ileum.
1. We have investigated the effect of the NO synthesis inhibitors, NG-monomethyl L-arginine (L-NMMA) and NG-nitro L-arginine (L-NOARG) on the non-adrenergic non-cholinergic (NANC) relaxation produced by electrical field stimulation in the circular muscle of the human ileum. 2. In the presence of atropine and guanethidine (1 and 3 microM, respectively), electrical field stimulation produced tetrodotoxin-sensitive relaxation of the strips. L-NMMA, starting from 100 microM, produced a concentration-dependent inhibition of the evoked relaxations (2Hz); maximal inhibition at 1 mM averaged about 35%. 3. The inhibitory effect of L-NMMA was unchanged by previous incubation with D-arginine while it was prevented by L-arginine (L-Arg). L-NMMA did not affect isoprenaline-induced relaxation. 4. L-NOARG (1-30 microM) concentration-dependently inhibited the evoked relaxations at 2 Hz, up to a maximum of 65% inhibition, although in some strips complete inhibition of the response was observed. The effect of L-NOARG was reversed by L-Arg. L-NOARG did not affect isoprenaline-induced relaxation. 5. These results suggest that NO may be involved in inhibitory NANC transmission in the circular muscle of the human ileum.
Maggi
C A
CA
Pharmacology Department, A Menarini Pharmaceuticals, Italy.
Barbanti
G
G
Turini
D
D
Giuliani
S
S
D001120:Arginine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007082:Ileum / Q000187:drug effects; D066298:In Vitro Techniques; D009126:Muscle Relaxation / Q000187:drug effects*; D019335:Nitroarginine; D019323:omega-N-Methylarginine
D019335:Nitroarginine; D019323:omega-N-Methylarginine; D001120:Arginine