Effects of oral L-NAME during Trichinella spiralis infection in rats

We investigated the involvement of nitric oxide in transmural jejunal alterations induced by Trichinella spiralis (T. spiralis) infection in rats. Rats were gavaged with either saline or T.spiralis larvae, and, 1 h later, rats were treated orally with water, NG-nitro-L-arginine methyl ester (L-NAME; 30 mg/kg), or NG-nitro-D-arginine methyl ester (D-NAME; 30 mg/kg) on a daily basis. Although not observed in jejunum from uninfected rats, inducible nitric oxide synthase (iNOS) mRNA was present in the mucosa and neuromuscular layers of jejunum from T. spiralis-infected rats. On day 6, T. spiralis-infected rats had a 6-fold decrease in transmural nitric oxide synthase activity, an 11-fold increase in plasma nitrite, and a 7-fold elevation in transmural myeloperoxidase (MPO) activity compared with uninfected controls. Intestinal smooth muscle cell hyperplasia and hypertrophy were only detected in the infected rats. L-NAME, but not D-NAME, treatment of infected rats for 6 days caused a pronounced increase in transmural iNOS mRNA expression, coinciding with significantly increased mucosal nitric oxide synthase activity. T. spiralis numbers in L-NAME-treated rats were significantly lower compared with the other two infected groups although L-NAME had no direct effect on T. spiralis viability in vitro. Furthermore, L-NAME treatment significantly reduced plasma nitrite and jejunal MPO but not intestinal smooth muscle cell hyperplasia or hypertrophy. In contrast, D-NAME treatment of infected rats significantly enhanced intestinal smooth muscle hyperplasia and hypertrophy. Taken together, these results suggest that alterations in the T. spiralis-infected jejunum are mediated, in part, by a suppression of nitric oxide synthase activity in the inflamed jejunum.