Effect of Cold Exposure on Levels of IL-2, IL-6, ACTH and Cortisol in Plasma of Piglets*

Abstract

Eighteen Yorkshire piglets aged 45 d were divided into 3 groups randomly. Group 1 (control) was kept at ambient temperature (18~20 ℃). Group 2 (Cold exposure) was kept at 4~8 ℃ for 12 hour. Group 3 (Cold exposure + RU486) was disposed by hypodermic injection (20 mg/kg body weight) and kept at temperature of 4~8 ℃ for 12 h. Blood samples were collected at 0 h, 1 h, 3 h, 6 h, 9 h and 12 h after cold exposure from superior vena cava. The levels of IL-2 and IL-6 in plasma were measured by the method of double antibody sandwich ELISA. The levels of ACTH and cortisol in plasma were evaluated by the RIA (Radio-immunity analysis) method. The results showed that of group 2 the levels of IL-2 and IL-6 increased significantly at 6 h (P0.01), the level of ACTH decreased significantly at 1 h, 3 h, 6 h and 12 h (P0.01) and the level of cortisol increased obviously at 3 h (P0.01). There was a strong correlation between the levels of IL-2 and IL-6 (r=0.959 5), a moderately negative correlation between ACTH and IL-2 (r=-0.435 9), a weakly negative correlation between ACTH and IL-6, a weakly negative correlation between cortisol and IL-2, and a moderately negative correlation between cortisol and IL-6 (r=-0.447 8). Of group 3 the IL-2 level increased remarkably at 6 h, 9 h and 12 h under cold exposure (P0.01) and rose slightly at 3 h (P0.05), the level of IL-6 rose obviously at 6 h (P0.01) and slightly at 1 h (P0.05), the level of ACTH decreased dramatically at 1 h, 3 h, 6 h, 9 h and 12 h (P0.01). There was a moderate correlation between the levels of IL-2 and IL-6 (r=0.416 1), a strongly negative correlation between ACTH and IL-2/IL-6 (r=-0.676 5/-0.717 4) and a weakly negative correlation between cortisol and IL-2/ IL-6. Those results suggested that the acute exposure at low temperature enhanced the secretion of IL-2, IL-6 and cortisol, and the blockage of GR could induce the changes of correlation between IL-2 and IL-6, and ACTH and IL-2/IL-6.