Overexpression of heat shock protein 70 and its relationship to intestine under acute heat stress in broilers: 1. Intestinal structure and digestive function.

The objective of this study was to investigate the relationship between heat shock protein 70 (HSP70) overexpression and intestinal structure and digestive function in heat-stressed broilers. In total, 240 male broilers were injected intraperitoneally with l-(1)-glutamine (0.75 mg/kg of BW) or quercetin (5 mg/kg of BW). Twenty-four hours later, they were heat-stressed for 0, 2, 3, 5, and 10 h, respectively, under 36 ± 1°C. The HSP70 protein and mRNA expression were obviously elevated at 3 h of heat stress, and glutamine induced the overexpression of HSP70 in the jejunal mucosa at different heat-stress times (P < 0.01). No significant change of jejunal villus height, crypt, and villus height:crypt ratio were observed after heat stress, and there were no effects of HSP70 overexpression on intestinal morphology under heat stress. The overexpression of HSP70 significantly increased alkaline phosphatase activity at 3 h of heat stress (P < 0.01). There was a strong correlation between HSP70 expression and the digestive enzyme activity (P ≤ 0.001). The overexpression of HSP70 significantly increased the amylase, lipase, and trypsin activity under heat stress (P < 0.001). These results demonstrated that glutamine was a good HSP70 enhancer to establish an HSP70 overexpression model. Although the overexpression of HSP70 did not change intestinal morphology conditions, it significantly increased broiler digestive enzyme activity under heat stress.