| GCs are steroid hormones with nerves activity,and are essential for development of central neverous system. Since Liggins reported that perinatal GCs therapy could reduce morbidity of NRDS,GCs have been used for more than thirty years in obstetrics.Recently more people begin to use repeated courses of GCs therapy.There is growing tendence that exposure of the fetal brain to excess GCs,at critical stages of development ,can have life-long effects.The purpose of this study is to investigate the effects of antenatal different courses GCs on the activity of 11-beta-hydroxysteroid dehydrogenase1, 11-beta-hydroxysteroid2, ornithin decarboxylase and evaluate effect on fetus brain development in different courses for using GCs effectively.Materal and MethodsHealthy female SD rats of three-month-old(n=30),were mated in estrus.It could produces accurately time-dated pregnant rats by the method of vaginal smear,pregnant rats on day 18(E18) were divided into three groups randomly: :repeated courses group , single course group and control group.Repeated courses group were given intramuscular dexamethasone (0.48mg/kg.dose) at E18 with q4h,a course contains four doses ,and lasted for three days;single course group,pregnant rats were given intramuscular dexamethasone for one course on E18,the other two days received equivalent volume of normal saline ,control groups received equivalent volume of normal saline for three days since E18.All three groups were allowed to deliver naturally.Pups were narcohypnosis on postenatal day3(P3), day7(P7), day15(P15), extracting brain and analysising 11-beta-hydroxysteroid dehydrogenase1; 11-beta-hydroxysteroid dehydrogenase2; and ornithin carboxylase. activity of hippocampus by immunohistochemistry.Results1. The effect on activity of 11-beta-hydroxysteroid dehydrogenase1 of hippocampus after antenatal different courses GCs.Immunohistochemistry showed that activity was expression in hippocampus in all groups. Biosens Digital Imagine displayed that repeated courses group was higher than control one P7(p<0.01),there was the same change on P15(p<0.01);No difference between single course and control group on P7 and P15 was found. (P>0.05). But there was significanct difference between repeated group and single course on P7 and P15(P<0.05).2. The effect on activity of 11-beta-hydroxysteroid dehydrogenase2 of hippocampus after antenatal different courses GCs11-beta-hydroxysteroid dehydrogenase2 activity wasn't expressed in the hippocampus in all groups,which indicated that there isn't 11-beta-hydroxysteroid dehydrogenase2 in the hippocampus, thereby 11-beta-hydroxysteroid dehydrogenase2 cannt reduce toxicity of GCs.3. The effect on activity of ornithin decarboxylase of hippocampus after antenatal different courses GCsImmunohistochemistry showed that ODC activity in all groups was different in the hippocampus until P3,with the lowest level in repeated courses and the highest level in control group (P<0.01);no significant difference between single course and control group was found (P>0.05);but there was difference between repeateded courses and single course.By 15d, ODC activity was also higher in repeated courses and the lowest in single one;almost disappear in control one.There was significant difference between repeated courses and control group(P<0.01).The same change occurred between repeated courses and single one (P<0.05),but no difference between single course and control group(P>0.05).4. Result of HE stainingThere are no abnormality in HE staining of brain after different courses antenatal dexamethasone.Conclusions1. 11-beta-hydroxysteroid dehydrogenase1 in hippocampus increase on P7 after antenatal dexamethsone,which lasted over two weeks.2. There was no effect on 11-beta-hydroxysteroid dehydrogenase2 activity in hippocampus after antenatal dexamethsone.3. Ornithin decarboxylase activity was suppressed after antenatal dexamethsone on P3,then increased significantly,which lasted for two weeks . |
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