Endogenous nitric oxide promotes ileal absorption.
OBJECTIVE
Nitric oxide (NO) is generated in vascular endothelium and enteric neural plexuses from L-arginine by the action of nitric oxide synthase (NOS). This study tested the hypothesis that NO is a modulator of ileal water and ion transport.


METHODS
NADPH diaphorase staining was performed on fixed frozen sections of canine ileum. Absorption studies (n = 80) were performed in five dogs with 25-cm ileal Thiry-Vella fistulas (TVF). Perfusion with [14C]PEG was used to calculate absorption of water, ions, and glucose from the TVF. Experiments comprised three 1-hr periods: basal, drug infusion, and recovery. Drugs infused luminally at 5 x 10(-4) mol/liter included L-ARG (NOS substrate), L-NAME (NOS inhibitor), L-ARG/L-NAME combination, D-ARG (inactive enantiomer of L-ARG), L-LYS (basic amino acid control for L-ARG), and SNAP (NO donor).


RESULTS
NADPH diaphorase staining indicated NOS activity in the ileal mucosa and submucosa. L-ARG and SNAP caused significant increases in water and ion absorption, whereas L-NAME caused significant decreases. The prosecretory effect of L-NAME was completely reversed by synchronous L-ARG. D-ARG and L-LYS had no significant effects. No infused agent influenced [14C]PEG recovery.


CONCLUSIONS
Inhibition of endogenous NO synthesis by L-NAME causes a prosecretory response for water and ions, which can be reversed by the administration of NOS substrate L-ARG. These results are consistent with the hypothesis that endogenous NO maintains a proabsorptive influence on water and ion transport in the ileum.
Maher
M M
MM
Department of Surgery, Johns Hopkins Medical Institutions, Baltimore, Maryland 21287-4606, USA.
Gontarek
J D
JD
Jimenez
R E
RE
Cahill
P A
PA
Yeo
C J
CJ
D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001834:Body Water / Q000378:metabolism; D004285:Dogs; D004573:Electrolytes / Q000378:metabolism; D005260:Female; D007082:Ileum / Q000378:metabolism*; D007408:Intestinal Absorption; D009252:NADPH Dehydrogenase / Q000378:metabolism; D019331:NG-Nitroarginine Methyl Ester; D009569:Nitric Oxide / Q000502:physiology*; D009599:Nitroprusside / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000493:pharmacokinetics
D004573:Electrolytes; D009599:Nitroprusside; D009569:Nitric Oxide; D011092:Polyethylene Glycols; D001120:Arginine; D009252:NADPH Dehydrogenase; D019331:NG-Nitroarginine Methyl Ester