A VASOACTIVE INTESTINAL POLYPEPTIDE-LIKE PROTEIN EXCRETED SECRETED BYNIPPOSTRONGYLUS-BRASILIENSIS AND ITS EFFECT ON CONTRACTION OF UNINFECTED RAT INTESTINE

The 50-30 kDa fraction isolated from the excretory/secretory products (E/S) of the nematode Nippostrongylus brasiliensis significantly decre ased the amplitude of contraction of segments of uninfected rat intest ine when injected into the lumen of the segments maintained in an orga n bath. Dot blot analysis of the fraction suggested that it was simila r in immunoreactivity to porcine vasoactive intestinal polypeptide (VI P). When antiserum to porcine VIP was mixed with N. brasiliensis E/S a nd the mixtures were injected into the lumen of segments of rat intest ine, the inhibitory effect of the E/S on amplitude of contraction decr eased. 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 ana lysis 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 s ynthesis of the peptide occurs inside the nematode. Peptide histidine isoleucine (PHI)-like immunoreactivity was detected in a 68 kDa fracti on of the E/S and the homogenate but this fraction did not affect the amplitude of contractions of the intestine.