A vasoactive intestinal polypeptide-like protein excreted/secreted byNippostrongylus brasiliensisand its effect on contraction of uninfected rat intestine

Abstract

SUMMARYThe 50–30 kDa fraction isolated from the excretory/secretory products (E/S) of the nematodeNippostrongylus brasiliensissignificantly decreased the amplitude of contraction of segments of uninfected rat intestine when injected into the lumen of the segments maintained in an organ bath. Dot blot analysis of the fraction suggested that it was similar in immuno-reactivity to porcine vasoactive intestinal polypeptide (VIP). When antiserum to porcine VIP was mixed withN. brasiliensisE/S and the mixtures were injected into the lumen of segments of rat intestine, the inhibitory effect of the E/S on amplitude of contraction decreased. When physiological concentrations of porcine VIP (12·9 pmol/ml) were injected into the lumen of segments of uninfected rat intestine the amplitude of contraction decreased significantly. Western blot analysis of the E/S, using antiserum to porcine VIP, recognized a 30 kDa protein in the E/S and also in whole worm homogenate suggesting that synthesis of the peptide occurs inside the nematode. Peptide histidine isoleucine (PHI)-like immuno-reactivity was detected in a 68 kDa fraction of the E/S and the homogenate but this fraction did not affect the amplitude of contractions of the intestine.