The effects of thermal acclimation on cardiac cellular signalling pathways in rainbow trout (Oncorhynchus mykiss)

Abstract

Rainbow trout (Oncorhynchus mykiss) experience seasonal variations in temperature between 4°C and 20°C. Cold acclimation causes cardiac hypertrophy and an increase in cardiac collagen, while warm acclimation has the opposite effect. The cellular mechanisms behind temperature-dependant cardiac remodelling are unclear. We hypothesized that temperature-dependant cardiac remodelling is regulated by the phosphorylation of mitogen-activated protein kinase (MAPK) cell signalling pathways. To test this, trout were acclimated to summer (18°C) and winter (4°C) then sampled over 8 weeks. p38 MAPK phosphorylation increased 2 weeks after summer acclimation in females. In males, at week 0, ERK phosphorylation increased following winter acclimation, and decreased following summer acclimation. These results indicate that thermal acclimation has significant effects on the phosphorylation of MAPKs and that these changes vary between sexes. Additionally, the lack of robust changes in heart composition suggest that other factors such as photoperiod and sex hormones may impact the remodelling response.