The effect of cu-melanocyte stimulating hormone (alpha -MSH) on colonic inf
lammation in the rat. In this study, we investigated the effects of alpha -
MSH administration on trinitrobenzene sulfonic acid-induced colitis and the
role of nitric oxide and prostaglandins in this response. (alpha -MSH trea
tment (25 mug/rat, intraperitoneally; twice daily for 3 days) reduced the c
olonic macroscopic lesions compared to untreated ones in both acute and chr
onic colitis groups. This effect was reversed by pretreatment with the nitr
ic oxide donor, sodium WP (4 mg/kg, intravenously) or cyclooxygenase-l sele
ctive antagonist indomethacin (5 mg/kg, subcutaneously) in the acute group
and with the cyclooxygenase-2 selective antagonist nimesulide (3 mg/kg, sub
cutaneously) in the chronic group. alpha -MSH had no effect on colonic wet
weight and myeloperoxidase acitivity compared to the untreated colitis grou
p. However, protein oxidation was markedly elevated in the alpha -MSH-treat
ed group compared to untreated ones. Nitroprusside and indomethacin reverse
d the effect of alpha -MSH on macroscopic lesions in the acute groups, wher
eas nimesulide showed a similar effect in the chronic group. In conclusion,
the results of our study show a protective role of alpha -MSH on colonic l
esions which partially involves nitric oxide and prostaglandins. (C) 2000 E
lsevier Science Inc. All rights reserved.