THE EFFECT OF GAMMA-RADIATION AND HEAT-SHOCK ON PROTEIN-SYNTHESIS ANDANTIOXIDANT ENZYMES IN THE GASTROINTESTINAL PARASITE, HELIGMOSOMOIDES-POLYGYRUS

Protein synthesis and antioxidant enzyme activities were investigated in gamma-irradiated (300 Gy) and heat shocked (42 degrees C) larval st ages of the gastrointestinal parasite, Heligmosomoides polygyrus baker i (H. polygyrus). No qualitative or quantitative differences were obse rved in the incorporation of (S-35)-methionine into somatic proteins o f unirradiated or irradiated exsheathed third-stage (L3) larvae at eit her 37 degrees C or 42 degrees C, The rate of protein synthesis double d in L3 stages maintained at 42 degrees C compared with 37 degrees C, irrespective of whether the larvae had been irradiated or not. The com position of excretory/secretory (ES) proteins varied between unirradia ted and irradiated exsheathed L3 larvae maintained under identical con ditions, Prominent heat-inducible proteins of 26 and 17 kDa were synth esised and excreted at 42 degrees C by both unirradiated and irradiate d L3 stages. No major differences in protein synthesis could be detect ed between unirradiated and irradiated fourth-stage (L4) larvae, Tempe rature elevation significantly reduced protein synthesis in L4 stages, most notably in unirradiated parasites. Heat-inducible proteins were not detected in response to either irradiation or temperature elevatio n in L4 larvae. Immune sera recognised a similar spectrum of antigens in both unirradiated and irradiated L4 somatic and ES preparations and reacted with antigens from irradiated L4 parasites with less intensit y than,vith antigens from unirradiated L4 larvae. Catalase was the onl y antioxidant enzyme examined with activity that changed significantly in irradiated parasites, being reduced to approximately 36% of normal levels in irradiated L4 stages, No significant difference existed bet ween irradiated and unirradiated parasites in the levels of activity o f superoxide dismutase and glutathione reductase. Copyright (C) 1996 A ustralian Society for Parasitology.