S. Aiko et al., EFFECTS OF NITRIC-OXIDE SYNTHASE INHIBITION OR SULFASALAZINE ON THE SPONTANEOUS COLITIS OBSERVED IN HLA-B27 TRANSGENIC RATS, The Journal of pharmacology and experimental therapeutics, 284(2), 1998, pp. 722-727
The objective of this study was to determine the effects that certain
nitric oxide synthase inhibitors have on the spontaneous intestinal an
d colonic inflammation that develops in HLA-B27 transgenic rats and co
mpare these data to those obtained using sulfasalazine (SZ). In an att
empt to more closely mimic the clinical situation, drug treatment was
begun after he onset of colitis, HLA-B27 male rats that developed clin
ical signs of colitis (diarrhea/loose stools) at 17 wk of age were ran
domized into fours groups consisting of one untreated colitic group an
d three treatment groups that received either aminoguanidine (AG; 52 m
u mol/kg/day), N-G-nitro-L-arginine methyl ester (L-NAME; 45 mu mol/kg
/day) or SZ (130 mg/kg/day) in their drinking water for 14 days. Aged-
matched Fisher 344 male rats were used as healthy controls. After 3 wk
of treatment, ileal and colonic mucosal permeabilities, granulocyte i
nfiltration and nitric oxide were quantified using blood-to-lumen clea
rance of Cr-51-EDTA, tissue myeloperoxidase activity, and plasma level
s of nitrate and nitrite, respectively, We found that both AG and L-NA
ME but not SZ significantly attenuated the increases in plasma nitrate
and nitrite levels. Interestingly, all three drugs were effective at
significantly attenuating the increases in myeloperoxidase activity in
the distal colon, Treatment with AG and SZ but not L-NAME were effect
ive at significantly attenuating the increase in ileal and colonic per
meabilities. Quantitative histological analysis revealed that AG and L
-NAME but not SZ significantly attenuated the increase in the mucosal
thickness and crypt depth in the distal colon compared to untreated co
litis. Taken together, these data demonstrate that oral administration
of certain nitric oxide synthase inhibitors or SZ to animals with act
ive colitis attenuates the colonic inflammation by at least two differ
ent mechanisms, One mechanism appears to be dependent on inhibition of
NO production whereas the other mechanism does not.