The effect of γ-radiation and heat shock on protein synthesis and antioxidant enzymes in the gastrointestinal parasite, Heligmosomoides polygyrus

Protein synthesis and antioxidant enzyme activities were investigated in γ-irradiated (300 Gy) and heat shocked (42°C) larval stages of the gastrointestinal parasite, Heligmosomoides polygerus bakeri (H. polygyrus). No qualitative or quantitative differences were observed in the incorporation of (35S)-methionine into somatic proteins of unirradiated or irradiated exsheathed third-stage (L3) larvae at either 37°C or 42°C. The rate of protein synthesis doubled in L3 stages maintained at 42°C compared with 37°C, irrespective of whether the larvae had been irradiated or not. The composition of excretory/secretory (ES) proteins varied between unirradiated and irradiated exsheathed L3 larvae maintained under identical conditions. Prominent heat-inducible proteins of 26 and 17 kDa were synthesised and excreted at 42°C by both unirradiated and irradiated L3 stages. No major differences in protein synthesis could be detected between unirradiated and irradiated fourth-stage (L4) larvae. Temperature 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 elevation 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 intensity than with antigens from unirradiated L4 larvae. Catalase was the only 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 between irradiated and unirradiated parasites in the levels of activity of superoxide dismutase and glutathione reductase.