| The Epidemiological studies have shown that pre - menopausal women are at relatively decreased risk of cerebral stroke when compared with men in the same age, and the serious degree of ischemic injury is much lower than the matched men and post - menopausal women in the same age. But the stroke incidence is taken bad when women go into the post - menopausal period. It has been found in many studies that the relative risk and mortality of stroke decreased in post - menopausal women who had received estrogen replacement therapy. So people presume that estrogen has a cererbral protective function.In resent study we observed the infarction areas and expression of Bel - 2 protein in the brains of male rats treated with different dose of estrogen, which were induced in middle cerebral artery occlusion, to investigate the cerebral protective effect of estrogen and its correlation with Bel - 2 protein expression, so that we can make further study to find out the mechanism of cerebral protection of estrogen.Materials and methods1. Experiment animal and their groupsAll the 40 healthy male Wistar rats, which were aged above 4 months and weighed 250 - 300g, were randomly divided into 6 groups named respectively as Group A, B, C, D, E, F( All rats were provided by Shenyang institute for drug control). Group A is ischemic control group, in which the rats were treated with 1ml saline each day (n = 8 ) ; Group B - D are estrogen - treated groups, in which the rats were given estrogen respectively in 0. 2 mg/ kg weight, 1 mg/ kg weight and 5 mg/ kg weight each day ( n = 8 ) ; Group E is normal control group (n =4) ; Group F is sham operated group (n =4) , in which the rats were induced in MCAO with a 15mm - length filament, the remaining steps were as same as Group A. All drugs were injected from the rats'belly cavity.2. MethodsAfter 6 days'treatement the rats in group A, B, C, D, F were induced intraluminal filament occlusion of middle cerebral artery for 24 hours and then were killed. Brain tissues were embedded in paraffin, coronally sectioned (7um) and then were made HE staining and Bel -2 immunohistochemical staining. The infarction area of HE staining and the value of positive cells of Bel - 2 were measured by pathological image analysis system. The values were made comparisons in each two groups by t - test and the correlation between the plasma density of estrogen and the values of Bel - 2 were analyzed by regression and correlation of line.Result1. Plasma estradiol density of the ratsPlasma estradiol density of the rats in Group F, A, B, C, Dwere 4.6 ±0.7 pg/ ml, 4.2 ± 1.1 pg/ml, 7.0 ±1.1 pg/ml, 53.4 ±6.0 pg/ ml and 53.4 ± 13.9 pg/ ml, respectively.2. The infarction areas of Group A - FThere were no infarction areas in Group E and F. The infarction areas of the rats in group A - D were 85.2 ± 8.33 mm2, 61.55 ±5.92 mm2, 36. 13 ± 10. 21 mm2 and 61. 40 ± 7. 17 mm2, respectively. Compared with the ischemic control group ( Group A) , all estrogen -treated groups ( Group B - D) had significantly less infarction areas (P<0.01 byt- test). Group C had less infarction area than Group A and Group D (P<0.01 byt- test) , and there was no obvious difference in infarction area between Group A and Group D(P>0.25 by t -test).3. The values of Bcl - 2 cells stained by immunohistochemical methodThere were no Bcl - 2 cells in Group E and Group F. Compared with the ischemic control group (Group A) , all the estrogen -treated groups (Group B -D) had significantly more Bcl-2 cells (P<0.01 by t - test). Group C had more Bcl -2 cells than Group A and Group D (P <0.01 by t - test). There were more Bcl -2 cells in Group A than in Group D (P<0.05 by t-test).4. The correlation between plasma estradiol density and the value of Bcl-2 cellsThere was a positive correlation between the plasma estradiol density and the value of Bcl -2 cells, r =0.41, P <0.05.ConclusionEstrogen can provide a cerebral protective effect against cerebral ischemic injury in the male rats, which was hi...
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