Effects of chronic heat stress on kidney damage, apoptosis, inflammation and HSPs of Acipenser baerii

Chronic heat stress caused by global warming can have serious implications for fish survival. The kidney plays a central role in many homeostatic functions, including water and electrolyte regulation, as well as acid-base balance. However, there is limited knowledge about the effect of heat stress on fish kidneys, especially in cold-water fish species. In this study, we investigated the effects of mild heat stress (24℃, M) and high heat stress (28℃, H) on A. baerii kidneys using histological observation, flow cytometry detection, and RT-qPCR. Our histological observations revealed that heat stress significantly caused infiltration of inflammatory cells in the kidney, especially at 28℃. The flow cytometry assay demonstrated a significant increase in the number of apoptotic cells after heat stress at 28°C compared to the control group at 20°C ( P < 0.05). Meanwhile, the mRNA expression levels of inflammation factors ( IL-1β and TNF-α ) did not differ significantly. However, the mRNA expression levels of heat shock proteins ( HSP70 , HSP90 , and GRP75 ) were increased in A. baerii . In summary, this study provides insight into the effect of heat stress on A. baerii kidneys and contributes to understanding the coping strategies of cold-water fish to chronic heat stress.