Nitric oxide production is diminished in colonic circular muscle from acquired megacolon.
OBJECTIVE
Nitric oxide modulates human colonic smooth muscle function. To determine whether nitric oxide production is altered in colon from acquired megacolon, we measured cholinergic nerve-mediated contractions in vitro before and after inhibition of nitric oxide synthase.


METHODS
Intramural nerves in circular smooth muscle from histologically normal colon (n = 12) and acquired megacolon (n = 3) were activated by electrical field stimulation.


RESULTS
In controls blockade of nitric oxide synthase by N(G)-Nitro-L-Arginine induced increases (P < 0.05) in amplitude of contractions; these increases in amplitudes were blocked by L-Arginine (analysis of variance; P < 0.05). By contrast, blockade of nitric oxide synthase did not increase amplitudes of contractions with circular smooth muscle from acquired megacolon. An immediate phasic contraction was blocked by atropine sulfate.


CONCLUSIONS
The results support the concept that nitric oxide production modulates cholinergic nerve-mediated contractions in normal colonic circular muscle, whereas acquired megacolon is associated with altered release of this inhibitory neurochemical. Potential explanations include depletion of tissue L-Arginine, decreased capacity to recycle citrulline to arginine, or decreased release of vasoactive intestinal peptide from circular smooth muscle in acquired megacolon.
Koch
T R
TR
Section of Gastroenterology, L. A. Johnson VA Medical Center and West Virginia University, Morgantown 26506-9161, USA.
Otterson
M F
MF
Telford
G L
GL
D000368:Aged; D000369:Aged, 80 and over; D003106:Colon / Q000378:metabolism*; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D008531:Megacolon / Q000378:metabolism*; D008875:Middle Aged; D009130:Muscle, Smooth / Q000378:metabolism*; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors
D009569:Nitric Oxide; D019001:Nitric Oxide Synthase