Sarcolipin but not phospholamban responds to in-vivo heat stress in rat skeletal muscle similar to the 70-kDa heat shock protein

Sarco/endoplasmic reticulum Ca²⁺ ATPase (SERCA) pumps are found on the membrane of the sarcoplasmic reticulum (SR) which actively transport Ca²⁺ from the cytosol into the SR. The 70-kDa heat shock protein (Hsp70), sarcolipin (SLN) and phospholamban (PLN) can preserve SERCA function in the face of heat stress (HS). However, it remains unknown if SLN and PLN can be stress-induced proteins like Hsp70. Therefore, the purpose of this study was to compare the SLN and PLN gene and protein time course (0, 24, and 48 h) response to <i>in-vivo</i> HS with that of Hsp70 in rat soleus (SOL) and white gastrocnemius (WG). The HS protocol involved submerging the lower limbs of the animals either in a 37 °C (control) or 44 °C-45 °C (HS) water bath for 30 min. We detected increases in <i>Hsp70</i> gene expression in the male WG immediately post-HS and in the female SOL after 48 h. Similarly, protein expression was induced after 24 h in both the muscles of males and in the female WG, and remained elevated after 48 h in the male SOL. SLN gene expression was induced in the male WG after 48 h and a trending increase was found for protein expression in the male SOL following HS. In contrast, PLN did not show any signs of stress-induction in either muscle or sex. These results suggest that like Hsp70, SLN, but not PLN, is a stress-induced protein that responds to <i>in-vivo</i> HS in a sex- and muscle-specific manner.