PORTAL VEINS OF MICE INFECTED WITH SCHISTOSOMA-MANSONI EXHIBIT AN INCREASED REACTIVITY TO 5-HYDROXYTRYPTAMINE

In chronic severe infection with Schistosoma mansoni, portal hypertens ion and related vascular alterations usually develop as a consequence of granulomatous response to eggs, in order to investigate a putative direct effect of worms on the reactivity of their host portal vein, mi ce infected only with male wet-ms were used in the present study. An h igher reactivity to 5-hydroxytryptamine (5-HT) characterized by an inc rease in the maximal contraction and sensitivity was observed in porta l vein from infected mice compared to healthy mice. Blockade of NO-syn thase with I-NAME induced a small increase in 5-HT potency in portal v ein from non-infected mice without changing the amplitude of the contr actions, whereas it did not alter the reactivity of veins from infecte d mice. The present results show that unisexual infection of mice with male S. mansoni increased the reactivity of the portal vein to 5-HT w hich seems to be partially related to an alteration in the nitric oxid e release by endothelium.