Meeting Abstract
Trimethylamine oxide (TMAO) and heat shock protein 70 (HSP70) are intracellular components directly involved in the thermal stress response, both protecting protein function at elevated temperatures. This study examines the effect of increasing temperature on the simultaneous regulation of these constituents in vivo. Using two elasmobranch species with innately high levels of TMAO, we address whether there is coordination between TMAO and HSP70 during a 6°C increase in temperature over 72 hours. The spiny dogfish, Squalus acanthias, a species with no endogenous synthetic capacity for TMAO, was compared to the smoothhound, Mustelus canis, a synthesizing species. There was no difference in plasma or tissue TMAO content between individuals held at control or elevated temperature in either species. These data suggest that, at the level of the whole organism, elasmobranchs do not rely on this molecule to combat acute thermal fluctuations. HSP70 increased nearly three-fold with increasing temperature in the white muscle of S. acanthias but not M. canis. The elevated HSP70 in S. acanthias demonstrates that the characteristically high TMAO content in this species does not confer sufficient protection to offset the denaturing effects of elevated temperature. The lack of HSP70 accumulation in M. canis was surprising and may be explained by species-specific differences in thermal range and tolerance, also discussed here. Our findings are in contrast to previous studies conducted with elasmobranch cells in vitro that show accumulation of TMAO with thermal stress and subsequent suppression of the HSP70 response.
