Abstract: Objective To study the effects of different rearing environment, barrier facility+IVC, barrier facility+conventional cage and conventional environment facility+IVC on the stress level, immune function and hematology and blood biochemistry in clean rats. Methods Three groups of weanling clean rats with 3 in one cage were housed respectively in three different environments for 45 days before tests of neuroendocrine hormone, cytokines, hematology and blood biochemistry were conducted, and the results were compared by groups to discover the different effects of three rearing environment. Results Compared with the rats in barrier facility+conventional cage, the rats in barrier facility+IVC had lower levels of CORT, IL-2, IL-1α, TNF-α, WBC, IL-1β, Fractalkine, CREA, and higher levels of IL-1β, Fractalkine, BUN, Ca, Ca/P ratio, meanwhile, the rats in conventional environment facility+IVC had lower levels of CORT, MCP-1, TNF-α, GLU, CREA, and higher levels of IL-1β, Fractalkine, RBC, HGB, HCT, TP, ALB, UA, Ca, Ca/P ratio, K, CO₂. Moreover, rats housed in IVC in different environment facility also showed significant difference in IL-1β, IL-10, MCP-1, RBC, HGB, HCT, BUN, IL-1α, ALB, ALT, UA and K. Conclusions Acclimatization of clean rats to different rearing environment can cause diversity of stress background, cytokine baseline and hematology and blood biochemistry. It suggests choosing a good rearing environment base on the rearing goals, periods and the relative interfering factors to be avoided.

Key words: Clean rat, Acclimatization, Biological characteristics, Barrier environment