Effect of dexamethasone on cerebral white matter development of premature rats and its mechanism / 中国小儿急救医学

ABSTRACT

Objective By making models of premature animal,explores the effects of dexamethasone on the brain development of premature rats and its mechanisms.Methods Eighteen SD rats were randomly divided into high-dexamethasone(H-Dex) group,low-dexamethasone (L-Dex) group and normal saline(NS) control group,with 6 rats in each group.The pregnant rats in L-Dex group were injected with dexamethasone [0.1 mg/(kg·d)] from 16 to 18 days of pregnancy,while the pregnant rats in H-Dex group were injected with dexamethasone [0.5 mg/(kg· d)] ; the pregnant rats in NS control group were injected with 0.9％ NaCl of the same volume.All of the fetal rats were received after administrating caesarean operation on the day 19 of pregnancy.Rats were sacrificed at the directed time and brain tissue was prepared.Histological feature and the water content of the brains were observed.Level of apoptosis was measured by flow cytometry.The expressions of myelin basic protein (MBP) and interleukin(IL)-1β in brain tissue homogenate were detected by ELISA.Results (1) The brain water contents of rats in H-Dex group,L-Dex group and NS control group were (85.94 ± 0.54) ％,(86.08 ± 1.01) ％,(86.94 ± 0.82) ％.Compared with NS control group,the water contents of Dex group were lower (P ＜ 0.05).(2) Glial cells of brain cortex in L-Dex group and H-Dex group were more mature than in NS control group,and the changes in H-Dex group was more significant.(3) The expressions of MBP in brain tissue of H-Dex group,L-Dex group and NS control group were (5.73 ± 1.06) μg/mg,(5.46 ±0.77) μg/mg and (2.42 ±0.52) μg/mg.Compared with NS control group,Dex group was higher(P ＜0.05).While the expressions of IL-1β in brain tissue of H-Dex group,L-Dex group and NS control group were (249.05 ± 11.29) pg/g,(257.47 ± 9.33) and (292.66 ± 21.51) pg/g.Compared with NS control group,Dex group was lower(P ＜ 0.05).There was no significant difference between H-Dex group and L-Dex group(P ＞ 0.05).(4) The level of apoptosis in H-Dex group,L-Dex group and NS control group were (18.07 ± 1.63) ％,(6.88 ± 0.47) ％ and (2.00 ± 0.32) ％.Compared with NS control group,the level of apoptosis in Dex group was higher(P ＜0.05),and H-Dex group was higher than that in L-Dex group.Conclusion (1) Using dexamethasone prophylactic could promote the development of glial cells,reduce the water content,increase the expressions of MBP,and decrease the expressions of IL-1β in brain tissues.It indicates that dexamethasone may play a major role in maturation of fetal brain.(2) Using dexamethasone prophylactic could increase the amounts of the apoptosis cells,and this effect is dose-dependent.It indicates that dexamethasone may have a negative effect on the fetal brain and suggestes that using dexamethasone in premature infant should be cautious,and if it has to,using a lower dose.