Objective To study the effects of high temperature combined with ultraviolet for continuous 2-4 months on serum interleukin-21 (IL-21) levels in rats.
Methods A total of 112 healthy adult SD rats, (200±10) g, half male and half female, were randomly divided into control group, high temperature group, ultraviolet group, and combined group (high temperature+ultraviolet), with 14 female and 14 male rats in each group and raised separately. The rats were correspondingly exposed to high temperature(38±1) ℃ and ultraviolet (310 nm, 72μW/cm2) for 2 h per day. After continuous exposure for 2 or 4 months, the rats were sacrificed and serum IL-21 was measured by ELISA.
Results After being exposed to high temperature combined with ultraviolet for 2 months and 4 months, the final weight(428.57±12.94), (476.86±13.14) g and weight gain(183.29±11.74), (306.86±13.81) g of male SD rats were significantly lower than those of the control groupfinal weight:(493.57±17.12), (587.00±11.53) g; weight gain:(249.00±17.99), (414.43±12.41) g (all Ps < 0.05), respectively. No significant differences in body weight were found for female rats (P > 0.05). After continuous exposure for 2 months, no statistical difference was found in the spleen coefficients and thymus coefficients by all exposure treatments and by gender (P > 0.05). After continuous exposure for 4 months, the spleen coefficients of each exposed grouphigh temperature group:(1.311±0.037) ‰; ultraviolet group:(1.270±0.058) ‰; combined group:(1.197±0.024) ‰ were smaller than those of the control group(1.410±0.026) ‰ (P < 0.05); the thymus coefficient of male rats in the high temperature group(0.576±0.041) ‰ was lower than that of the control group(0.996±0.067) ‰ (P < 0.05); there was no difference in organ coefficients for the female rats administrated with different exposures (P > 0.05). Under the same exposure time and exposure treatments, there was no gender difference in serum IL-21 levels (P > 0.05); therefore, the female and male rats were merged for further analysis. Except the ultraviolet group after 2 months(487.69±15.21) ng/L, the levels of serum IL-21 in the other groups2 months:high temperature group, (365.05±18.17) ng/L, combined group, (278.66±11.70) ng/L; 4 months:high temperature group, (343.73±22.97) ng/L, ultraviolet group, (264.45±23.96) ng/L, combined group, (150.90±23.06) ng/L were significantly lower than those in the control group2 months:(518.11±18.68) ng/L; 4 months:(582.18±28.90) ng/L (P < 0.05). The serum IL-21 levels of the 4-month ultraviolet group and the combined group were lower than the corresponding values of the 2-month groups (P < 0.01). The level of serum IL-21 in the combined group was significantly lower than those of the high temperature group and the ultraviolet group treated for both 2 months and 4 months (P < 0.05).
Conclusion The combination exposure of high temperature and ultraviolet may affect body weight gain, immune organ weight, and serum IL-21 levels of rats, and serum IL-21 levels would decrease with prolonged exposure time.
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