OBJECTIVETo investigate the variation and the effect of TNF and NO in the process of the creation of protective heat stress model and provide more thoretical basis.

METHODSThe rats were properly treated with heat and then the serum was separated. Radioimmunoassay and nitrate reductase assay were employed to measure the concentration of TNF and NO at different time between 0 h and 24 h after heat stress respectively.

RESULTSCompared with the control, the concentration of TNF increased significantly 2 h, 4 h, 8 h, 12 h after heat stress, of which 2 h, 12 h(P < 0.05), 4 h, 8 h(P < 0.01), but no significant changes 0 h, 24 h after heat stress. The concentration reached the peak 4 h after heat stress[(3.35 +/- 0.20) ng/ml] and increased significantly than 0 h, 2 h, 8 h, 12 h, 24 h after heat stress(P < 0.01, P < 0.05). 24 h after heat stress it recovered to normal standard. Compared with the control, the concentration of NO was higher 2 h, 4 h, 8 h, 12 h, 24 h after heat stress(P < 0.05), but no significance at 0 h. The concentration amounted to peak 8 h after heat stress[(108.21 +/- 27.89) mumol/L] and increased than 0 h, 2 h, 4 h after heat stress(P < 0.01). After 8 h it began to decrease continuously in heat stress group, however it was higher 24 h after heat stress than control.

CONCLUSIONTNF and NO played an important role in the process of the creation of protective heat stress model.