Sodium azide, which inhibits cytochrome oxidase c and ATP synthase, creates a chemical hypoxia in cells and can induce certain heat shock proteins. It is a worm anesthetic but the mechanism by which C. elegans can survive prolonged exposure to this chemical is not known. We hypothesized that chemicals affecting energy metabolism induce the heat shock response in C. elegans and produce a thermotolerant worm. For control (no azide or heat exposure) worms taken directly to 37 o C, their survival probability (SP) = 0.07, while for worms exposed to 10 mM azide and then taken to 37 o C, their SP = 0.68 (p<0.05), thereby indicating azide induced thermotolerance. This compares well with worms exposed to 33 o C and then taken to 37 o C, SP = 0.92 (p<0.05). We then hypothesized that the molecular mechanism of the response to azide involves induction of the heat shock proteins. Using SDS-PAGE, Coomassie Brilliant Blue staining, and Western Blot analysis, we observed induction of
hsp70 and
hsp16, but the levels of induction were low when compared to worms exposed to 33 o C. To further elucidate this mechanism, we tested the only known hsp mutant,
daf-21 (
p673). Using our standard protocol, when grown at the permissive temperature, it demonstrated azide induced thermotolerance. At the restricted temperature, however, there was no azide induced thermotolerance. These results suggest that while
hsp90 is not induced by sodium azide, it is an essential part of the worm's response to stress. Azide induces thermotolerance in C. elegans by a mechanism similar to the heat shock reponse but at reduced levels of hsp induction. In light of the
daf-21 results, we examined other dauer mutants for their ability to undergo azide induced thermotolerance (see Lapoczka et al, this meeting), in addition to identifying intrinsically thermotolerant substrains of N2s (see Smith et al., this meeting).