Article date: February 1996
By: Diego Currò;, Anna Rita Volpe;, Paolo Preziosi, in Volume 117, Issue 4, pages 717-723
In the presence of atropine (1 μm) and guanethidine (5 μm), electrical field stimulation (EFS, 120 mA, 1 ms, 0.5–16.0 Hz, trains of 2 min) induced frequency‐dependent relaxations of 5‐hydroxytryptamine (3 μm)‐precontracted longitudinal muscle strips from the rat gastric fundus.
L‐Citrulline concentrations were measured in the incubation medium of precontracted strips before and after EFS to investigate nitric‐oxide (NO) synthase activity and its possible relation to non‐adrenergic non‐cholinergic (NANC) relaxation.
Basal NO synthase activity was reflected by the finding of prestimulation levels of L‐citrulline of 30 nM. These levels were unaffected by tetrodotoxin (3 μm) and NG‐nitro‐D‐arginine methyl ester (D‐NAME, 100 μm), slightly reduced by a calcium‐free medium and halved by NG‐nitro‐L‐arginine methyl ester (L‐NAME, 100 μm).
EFS evoked significant, frequency‐dependent increases in bath levels of L‐citrulline at all frequencies tested. The increases evoked by 16‐Hz EFS were abolished by tetrodotoxin (3 μm), a calcium‐free medium and L‐NAME (100 μm) but not by D‐NAME (100 μm).
L‐NAME (0.1 μm − 1.0 mM) produced significant reduction of 4‐Hz EFS‐induced L‐citrulline production (100% inhibition at 10 μm), but had less marked effects on basal production (50% reduction at 100 μm) and 4‐Hz EFS‐induced NANC relaxation (50% reduction at 1 mM).
L‐Arginine (1 mM), but not D‐arginine (1 mM), increased basal L‐citrulline levels and reversed the inhibitory effect of L‐NAME (10 μm).
These findings represent clear biochemical evidence of both basal and EFS‐stimulated NO synthase activity in the rat gastric fundus.
In the presence of atropine (1 μm) and guanethidine (5 μm), electrical field stimulation (EFS, 120 mA, 1 ms, 0.5–16.0 Hz, trains of 2 min) induced frequency‐dependent relaxations of 5‐hydroxytryptamine (3 μm)‐precontracted longitudinal muscle strips from the rat gastric fundus.
L‐Citrulline concentrations were measured in the incubation medium of precontracted strips before and after EFS to investigate nitric‐oxide (NO) synthase activity and its possible relation to non‐adrenergic non‐cholinergic (NANC) relaxation.
Basal NO synthase activity was reflected by the finding of prestimulation levels of L‐citrulline of 30 nM. These levels were unaffected by tetrodotoxin (3 μm) and NG‐nitro‐D‐arginine methyl ester (D‐NAME, 100 μm), slightly reduced by a calcium‐free medium and halved by NG‐nitro‐L‐arginine methyl ester (L‐NAME, 100 μm).
EFS evoked significant, frequency‐dependent increases in bath levels of L‐citrulline at all frequencies tested. The increases evoked by 16‐Hz EFS were abolished by tetrodotoxin (3 μm), a calcium‐free medium and L‐NAME (100 μm) but not by D‐NAME (100 μm).
L‐NAME (0.1 μm − 1.0 mM) produced significant reduction of 4‐Hz EFS‐induced L‐citrulline production (100% inhibition at 10 μm), but had less marked effects on basal production (50% reduction at 100 μm) and 4‐Hz EFS‐induced NANC relaxation (50% reduction at 1 mM).
L‐Arginine (1 mM), but not D‐arginine (1 mM), increased basal L‐citrulline levels and reversed the inhibitory effect of L‐NAME (10 μm).
These findings represent clear biochemical evidence of both basal and EFS‐stimulated NO synthase activity in the rat gastric fundus.
DOI: 10.1111/j.1476-5381.1996.tb15249.x
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