寒冷对雌性C57BL/6小鼠动情周期的影响*

目的:研究寒冷对雌性C57BL/6小鼠动情周期的影响。方法:12只雌性小鼠随机分为对照组、低温组,每组6只;低温组每天4℃暴露4 h,每天阴道涂片法观察小鼠动情状况,对照组饲养于常温动物房;每2 d称量体重,2周后心脏取血、子宫和卵巢,检测小鼠血清E2、FSH、LH、Prl、P水平,进行子宫、卵巢的组织病理学检查。结果:与对照组比较,低温组小鼠体重无显著性差异(P＞0.05),小鼠子宫脏器系数明显较低、动情间期明显延长(P＜0.01),血清FSH显著升高、Prl显著降低(P＜0.01),小鼠子宫腺管扩张,卵巢卵泡数量明显减少。结论:寒冷可使雌性C57BL/6小鼠动情周期延长,进而可能影响生殖功能。     

NOD/SCID雌性小鼠动情周期的观察

目的观察NOD/SCID小鼠动情周期及卵巢切除术后阴道涂片的变化。方法连续观察9 d NOD/SCID鼠,每日进行两次阴道涂片,计算动情周期时间及发生率。卵巢切除后,阴道涂片并观察阴道涂片变化。结果NOD/SCID小鼠动情周期为4~6 d。有规律动情的小鼠占80%。阴道口状态与动情周期无明显相关。卵巢切除术后,阴道涂片呈动情后期或动情间期改变。结论采用阴道脱落细胞涂片法可判断NOD/SCID雌性小鼠的动情周期及特点,NOD/SCID雌性小鼠卵巢切除手术有效。     

母代高脂饮食诱导子代在小鼠生命早期出现糖脂代谢紊乱且具有雄性易感性

目的：探讨孕期和哺乳期的高脂饮食能否导致子代在生命早期出现糖脂代谢紊乱。方法成年雌性C57BL/6J小鼠与正常饮食雄性小鼠进行交配,孕鼠随机分为高脂饮食组和正常饮食组,在孕期和哺乳期喂养高脂饲料或正常饲料,至交配后第一代鼠断乳时（3周龄）观察其糖脂代谢相关性指标以及肝脏病理表现。结果较正常饮食组子鼠相比,高脂饮食子鼠出生体重更低（ P＜0.05）。在断乳时,高脂饮食组雄性子鼠体重较重（ P ＝0.038）,腹腔糖耐量实验30 min和60 min血糖明显升高（P值分别为＜0.001和＜0.01）,糖耐量曲线下面积较大（P＝0.0016）,HOMA-IR值较大（P＜0.05）,雌性子鼠腹腔糖耐量实验在30 min血糖高于正常组（P＜0.01）,而糖耐量曲线下面积和HOMA-IR值在两组之间无明显统计学意义。雄性和雌性子代小鼠空腹胆固醇水平高脂饮食组均高于正常饮食组（ P值分别为＜0.0001和0.0004）,而两组雄性和雌性子代小鼠空腹胰岛素和甘油三酯水平差异均无显著性（ P均＞0.05）。另外,在断乳时高脂饮食子鼠出现肝脏脂肪变性,雌性和雄性子鼠无明显差异。结论母鼠孕期和哺乳期高脂饮食能够诱导子代在生命早期就能出现糖脂代谢紊乱并且雄性子鼠更易出现肥胖、糖耐量异常、胰岛素抵抗。     

低浓度84消毒液对小鼠生殖生理的影响

目的：观察低浓度84消毒液对小鼠生殖生理的影响。方法将72只KM小鼠随机分为3组,即：0.5％84消毒液组（ A组）、2.0％84消毒液组（ B组）和生理盐水组（ C组）,每组24只,雌雄各半,各组每天1次灌胃给予相应药物,连续9周。阴道涂片镜检观察雌性小鼠的动情周期。9周后,观察雄性小鼠的精子畸形率;并用ELISA法测定小鼠血清中性激素的水平;并取睾丸（或卵巢）、心、肝、肺、肾进行组织学观察。结果与C组比较,A和B组小鼠体重差异无显著性（ P ＞0.05）;血清性激素水平差异无显著性（ P ＞0.05）;雌性小鼠动情周期差异无显著性（P ＞0.05）;组织学观察未见异常;与C组比较,A组小鼠精子畸形率差异无显著性（P ＞0.05）,B组小鼠精子畸形率显著增高（ P ＝0.041＜0.05）。结论0.5％84消毒液对小鼠的生殖生理无明显影响,在实际使用中要严格控制消毒液浓度。     

妊娠晚期高雄环境对子代雌鼠性腺发育及生殖功能的影响

目的:通过观察妊娠晚期高雄环境对子代雌鼠性腺发育及生殖功能的影响,从而探讨多囊卵巢综合征(PCOS)的可能致病因素.方法:16只妊娠Wismr大鼠被随机分为A、B两组各8只(A为实验组,B为对照组),A,B两组大鼠均取妊娠第15-20天的相同时间于颈部皮下分别注射等量丙酸睾丸酮和中性茶油,均于孕2l天剖宫产,A组子代雌鼠14只,B组12只;观察子代雌鼠脐带血中睾酮(T)水平、出生体重、阴道开口时间和发情周期、出生100天时体重、乳房发育情况及卵巢、子宫的组织形态学改变.结果:①A组子鼠脐带血中睾酮(T)水平明显增高(P＜0.05);②A组子鼠出生体重较B组明显降低,而出生100天时A组子代雌鼠体重明显高于B组(P＜0.05);无明显发情周期;出生100天时乳房数明显低于B组;阴道开口时间较B组无明显差异③A组子代雌鼠子宫积水扩张明显,卵巢中闭锁卵泡较B组明显增加(P＜0.05).结论:妊娠晚期高雄环境下子代雌鼠表现出类似PCOS的性腺发育及生殖功能异常,推测妊娠晚期母体雄激素过高可能是PCOS的早期致病因素.     

不同周龄Balb/c小鼠脏器质量及其变化趋势分析

目的:测定不同周龄Balb/c小鼠主要脏器质量、脏器系数,并进行比较。方法:取120只3周龄、5周龄、7周龄的Balb/c小鼠,雌雄各半,精确测量小鼠体重和主要脏器质量,计算脏器系数。结果:①雌性与雄性Balb/c小鼠脏器质量相比较:3周龄时肝、脾有显著差异(P0.05);5周龄时肝有非常显著差异(P0.01),脾、肺有显著差异(P0.05);7周龄时肝、肺及双肾有非常显著差异(P0.01),心、脾有显著差异(P0.05)。②雌性与雄性Balb/c小鼠脏器系数相比较:3周龄时肝、脾有显著差异(P0.05);5周龄时肝、脾有非常显著差异(P0.01),膀胱有显著差异(P0.05);7周龄时肺、双肾有非常显著差异(P0.01),脾、膀胱有显著差异(P0.05)。结论:随着周龄的增长,Balb/c雌、雄性小鼠之间,存在差异的脏器也在增多。     

ApoE基因缺陷小鼠的心肌肥厚及辛伐他汀的干预研究

目的:观察高胆固醇喂养的不同周龄ApoE基因缺陷(ApoE-/-)小鼠心肌细胞和心肌间质成分的改变,并观察辛伐他汀对其的影响.方法:36只8周龄雄性ApoE-/-小鼠饲以高胆固醉饲料喂养8周即至16周龄,随机被分为三组继续喂养至24周龄组、32周龄组和40周龄组,每一周龄组为12只,再随机分为模型组6只和辛伐他汀干预组6只(25mg/kg/d),相同周龄的C57BL/6J小鼠设为对照.分别在24周、32周、40周结束时处死小鼠.常规检测血浆胆固醇水平,留取新鲜心脏组织测定总胆固醉及一氧化氮(NO)、超氧化物歧化酶(SOD)、丙二醛(MDA):另取心脏组织固定,石蜡切片,HE染色观察各组小鼠心肌细胞的变化,Masson染色观察心肌胶原改变.结果:24、32和40周龄模型组ApoE-/-小鼠血浆、心脏组织胆固醇和MDA水平逐渐增加(p<0.05),NO和SOD水平逐渐降低(p<0.05),心肌细胞直径和心肌胶原含量逐渐增加(p<0.05).与相同周龄模型组相比,辛伐他汀干预组血浆、心脏组织胆固醇和MDA水平明显降低(p<0.05),心肌细胞直径明显减小;40周龄辛伐他汀干预组左室壁平均厚度明显降低(p<0.05),32周龄和40周龄辛伐他汀干预组心肌胶原含量明显减少(p<0.05).结论:高胆固醇喂养的ApoE基因缺陷小鼠,随着周龄增加、胆固醇水平增加,抗氧化能力降低,心肌细胞直径和心肌胶原含量显著增加,辛伐他汀可能减轻心脏重构.     

C57BL/6J-HBV转基因小鼠随增龄乙肝表面抗原表达及转氨酶水平变化探讨

目的 探讨C57BL/6J-HBV乙肝转基因小鼠随增龄表面抗原表达及转氨酶水平的变化.方法 经血清表面抗原检测,根据S/C.O值将乙肝转基因小鼠分为两组,两组小鼠在4～10周龄每隔一周以酶联免疫吸附法测定血清表面抗原水平;各组小鼠在5～11周龄每隔一周以全自动生化分析仪测定小鼠血清谷丙转氨酶(ALT)和谷草转氨酶(AST)水平.结果 实验1组HBV乙肝转基因小鼠表面抗原表达6周龄与4周龄相比显著增高,6周龄至10周龄趋于稳定;实验2组的雄性小鼠表面抗原表达6周龄与4周龄相比极显著降低(P＜0.01),而雌性小鼠在4周龄至10周龄表面抗原表达相对稳定.实验1组的雄性小鼠ALT 水平9周龄与7周龄比较显著下降(P＜0.05),其余小鼠在5周龄至11周龄呈现下降趋势,但无显著性差异.实验1组的雄性小鼠AST水平11周龄与7周龄相比显著升高(P＜0.05).结论 乙肝表面抗原S/C.O值不同的转基因小鼠表面抗原表达随增龄变化趋势不同;血清谷丙转氨酶和谷草转氨酶水平在5～11周龄变化趋势相反.     

黄芪注射液对2型糖尿病动物模型KKAy小鼠脑微血管病变的影响

目的:观察黄芪注射液对2型糖尿病动物模型KKAy小鼠脑微血管病变的影响,探讨黄芪注射液对糖尿病脑血管病变的保护作用.方法:饲养至14周龄的雄性KKAy小鼠随机分成模型组和黄芪注射液治疗组(每日腹腔给药,剂量为3 mL/kg),同龄雄性C57BL/6J小鼠作为对照组.血糖仪测量20、24、28周龄时各组小鼠的空腹血糖水平.28周龄时处死各组小鼠,放射免疫法检测血清6-酮-前列腺素-F1α( 6-Keto-PGF1α)和血栓素B2(TXB2)的含量.透射电子显微镜观察脑组织超微结构变化.结果:模型组KKAy小鼠从20周龄开始血糖水平明显高于正常组小鼠(P＜0.01);黄芪治疗组小鼠从20周龄开始血糖水平明显高于正常组小鼠(P＜0.01),但低于模型组小鼠(P＜0.05或P＜0.01).模型组小鼠血清6-Keto-PGF1α水平较正常组降低(P＜0.01),TXB2含量增高(P＜0.01);与模型组相比,黄芪注射液治疗组小鼠6-Keto-PGF1α水平升高(P＜0.01),TXB2含量下降(P＜0.01).透射电镜显示模型组小鼠神经细胞胞核染色质疏松,线粒体肿胀,粗面内质网缩小,核糖体减少;治疗组小鼠以上病变明显改善.结论:黄芪注射液可以有效改善2型糖尿病动物模型KKAy小鼠脑微血管病变,保护神经细胞结构.     

硫辛酸对卵巢切除小鼠学习记忆的影响

目的:探讨硫辛酸(Lipoic acid,LA)对卵巢切除(ovariectomized,OVX)小鼠学习记忆的影响。方法:2月龄雌性昆明小鼠随机分为4组:假手术(Sham)组、OVX组、OVX+LA组、OVX+LA+左旋硝基精氨酸甲酯(L-NAME)组。建立卵巢切除模型并给药,Morris水迷宫检测各组小鼠学习记忆能力。结果:前4天定位巡航实验中,OVX组与Sham组相比,逃避潜伏期明显延长(P0.05),第5天撤除平台后,OVX组在目的象限游泳距离及时间百分比较Sham组明显缩短(P0.05);OVX+LA组与OVX组相比,逃避潜伏期明显缩短(P0.05),撤除平台后,在目的象限游泳距离及时间百分比明显延长(P0.05);OVX+LA+L-NAME组与Sham组相比,逃避潜伏期明显延长(P0.05),撤除平台后,在目的象限游泳距离及时间百分比明显缩短(P0.05)。结论:OVX损伤小鼠的学习记忆,LA可改善这种损伤,内皮型一氧化氮合酶(e NOS)抑制剂L-NAME可削弱LA的这种保护作用。     

CXCR4基因转染人脐带间充质干细胞移植治疗糖尿病肾病的实验研究

摘要 目的：探讨过表达CXCR4的人脐带间充质干细胞（human umbilical cord mesenchymal stem cell, hUC-MSCs）移植后对糖尿病肾病的治疗作用。方法：构建CXCR4的慢病毒表达载体，并建立过表达 CXCR4 的人脐带间充质干细胞（CXCR4-MSCs）。采用8周龄健康雌性SD大鼠75只，其中15只为正常对照组，60只为实验组。实验组糖尿病成模后一个月，将糖尿病实验大鼠60只随机分为4组：①移植CXCR4-MSCs组(CXCR4基因转染MSCs组)，即CXCR4组；②移植null-MSCs组(空质粒未转染CXCR4基因的MSCs组)，即null-MSCs；③移植MSCs组( MSCs组)；④PBS组(未移植任何的MSCs，单纯PBS注射，PBS组)。将CXCR4-MSCs、null-MSCs及MSCs消化离心，取含1×106个细胞悬液经尾静脉分别注入CXCR4-MSCs组、null-MSCs组及MSCs组大鼠体内，PBS组注射l mL PBS。干细胞治疗8周后，处死五组大鼠。各组大鼠处死前放代谢笼留取24 h尿，计算尿量，保存送检。处死前尾静脉采血检测血糖、称体重并记录。观察血糖、肾脏肥大指数、肾重、体重、24小时尿蛋白排泄量，并观察肾脏组织病理学改变。结果：60只SD雌性大鼠糖尿病模型成功率达100％，至实验8周糖尿病大鼠总共死亡14只，存活率达76.67％。实验开始后的8周，所有CXCR4组、Null-MSCs组、MSCs组、PBS组大鼠与正常组比较，体重均明显减轻(P<0.01)，血糖明显升高(P<0.01)。MSCs治疗后8周，除正常组外，其余各组大鼠血糖、肾重、肾重/体重比、24小时尿蛋白均显著增高，体重显著降低(P<0.05)；与PBS组相比，CXCR4组、null-MSCs组，MSCs组大鼠的肾重、肾重/体重比、24小时尿蛋白均明显降低(P<0.05)，体重无明显增加，血糖无明显降低(P>0.05)。CXCR4组大鼠的肾重、肾重/体重比、24小时尿蛋白较除正常组外的各组均明显降低(P<0.05)。糖尿病成模后，给予大鼠尾静脉注射干细胞悬液或等量培养液，注射后8周，除正常组外，其余各组PAS染色可见大鼠肾小球肥大，肾小球基底膜增厚、系膜增生、系膜基质增多，部分肾小球出现明显硬化，符合糖尿病肾病中期病理表现。CXCR4组大鼠肾小球系膜基质增生较其余各组大鼠减少(P<0.05)。结论：转染CXCR4的MSCs可改善糖尿病肾病。     

rAAV-shRNA-CDK2对肝癌人肝癌裸鼠血液系统的影响

目的:探讨新型基因药物rAAV-shRNA-CDK2对人肝癌裸鼠血液系统的影响,评估其安全性。方法:采用皮下接种人肝癌Hep G2细胞构建荷瘤裸鼠,10天后将其随机分为3组:肿瘤组、NC组及rAAV-shRNA-CDK2组,每组雌雄裸鼠各6只。通过尾静脉注射定量给药,15天后取眼球血并处死裸鼠。检测血常规指标和骨髓细胞周期。结果:所有裸鼠平均血小板体积略高于该周龄鼠的正常值范围,但各组间比较差异无统计学意义(P0.05);肿瘤组雌性裸鼠的中性粒细胞百分比显著高于rAAV-shRNA-CDK2组,而淋巴细胞百分比明显低于rAAV-shRNA-CDK2组(P0.05),但指标数值均在正常值范围内。各组雄性裸鼠骨髓细胞周期分布比较差异均无统计学意义(P0.05),而肿瘤组雌性裸鼠骨髓细胞G2/M期比例明显高于rAAV-shRNA-CDK2(P0.05),但两组其他周期骨髓细胞比例比较差异无统计学意义(P0.05)。结论:rAAV--shRNA-CDK2并未对人肝癌裸鼠血液系统产生不良影响。     

Influence of different doses of progesterone treatments on ovarian follicle status in beef cows

To determine a dose of progesterone (P4) that allow ovarian follicular wave control, Aberdeen Angus cows were randomly assigned into four groups: T600 (n=5), 600 mg of P4/day; T400 (n=5), 400 mg of P4/day; T200 (n=4), 200mg of P4/day and Control (n=4) (excipient only). Progesterone was injected from day 3 to 9 of estrous cycle. Ultrasonographies and blood sample collections were performed daily from day 2 to 10 and on day 15 of the estrous cycle. Additionally, an ultrasonographic study was conducted on day 13. Progesterone concentrations were different among all groups (P<0.01). The diameter of the dominant follicle was greater for control than for T200, T400 and T600 groups (P<0.01); there was no difference between T200 and T400 (P>0.05), but they had a greater diameter follicle than the T600 group (P<0.01). The growth rate of the dominant follicle between day 3 and 7 of estrous cycle was greater for control group (1.63+/-0.3 mmday(-1)) than for T200 (0.56+/-0.19 mmday(-1), P<0.05), T400 (0.6+/-0.23 mmday(-1), P<0.05) and T600 (0.11+/-0.13 mmday(-1), P<0.01) groups. The mean number of class I follicles (3-4mm) per day for the entire experimental period was less for the control group than for T200 (P<0.05), T400 and T600 (P<0.01) groups (3.7+/-1.3; 5.3+/-1.3; 6.6+/-1.8 and 8.1+/-1.9, respectively). The mean number for the T200 group was less than for T600 (P<0.05) and similar for T400 and T600 groups (P>0.05). The number of class III follicles was greater for control group than for the other groups (P<0.01). T200 and T400 groups had similar numbers of class III follicles (P>0.05) and both had greater numbers of follicles than the T600 group (P<0.05). The diameter of the corpus luteum of the T600 group (15.8+/-1.6 mm) was less than for control (21.0+/-2.5 mm, P<0.01), T200 (19.3+/-2.7 mm, P<0.01) and T400 (20.0+/-2.2 mm) groups (P<0.05). The mean diameter of corpus luteum of T200 was similar to T400 (P>0.05), but different from the control group (P<0.05). In conclusion, the daily intramuscular administration of 200mg or more of progesterone from day 3 to 9 of the estrous cycle indicates that plasma concentrations of progesterone can be used to modify the pattern of follicular development during the follicular wave. From day 5 of the estrous cycle, progesterone concentrations greater than 15 ng/ml (T600 group: 600 mg/day of progesterone from day 3 to 9 of the estrous cycle) inhibit dominant follicle development, increase the class I follicle populations (3-4 mm) and diminish the development of the corpus luteum.     

Studies on the relationship between paracoccidioidomycosis in ddY mice and their estrous cycle

The relationship between paracoccidioidomycosis in ddY mouse and its estrous cycle was studied. Adult ddY mice of both sexes were used as experimental animals. Estrous cycle of female mice was examined before inoculation of Paracoccidioides brasiliensis yeast cells and mice were divided into 5 groups such as proestrus, estrus, metestrus-I, metestrus-II and diestrus. Each mouse was inoculated intravenously with 10⁶ P. brasiliensis yeast cell units and sacrificed on day 28 after inoculation. Their internal organs were cultured, and in addition, their histopathologies were studied. As a result, there was no difference in the organ cultures among the male and the female mice of 5 groups. However, histopathologically, the female groups at estrus, metestrus-I and metestrus-II were affected more severely than the male group, and the susceptibility of the female mice to the fungus was closely related to their estrous cycles.Abbreviations BHI-D brain heart infusion agar supplemented with 1.0% of anhydrous dextrose - PAS periodic acid-Schiff techniques - PBS phosphate buffered saline solution - SD standard deviation     

Influence of the estrous cycle on hypoxic failure in the female rat heart

Background: Clinical studies have shown that fluctuation in the plasma concentrations of estrogen during the menstrual cycle has an effect on myocardial health in premenopausal women. When estrogen levels are low, the number of ischemic events experienced is increased.Objective: To determine whether the increased ischemic events reported with low plasma estrogen concentrations in women could be reproduced in an animal model, cardiac function was measured during hypoxia in the female rat at different time points of the estrous cycle.Methods: Hearts from female Sprague-Dawley rats were perfused in the working mode at the diestrous (low estrogen; n = 7) and proestrous (high estrogen; n = 6) phases of the estrous cycle, confirmed by plasma estradiol concentrations. Hearts were perfused under aerobic conditions with 5.5 mM glucose, 100 μU/mL insulin, and 1.2 mM palmitate, followed by a 30-minute period of hypoxia with 95% N₂-5% CO₂ gassing.Results: There were no significant differences in heart function between diestrous and proestrous groups prior to hypoxia. However, hypoxia induced perturbations in function that were dependent on the estrous cycle. Reductions in left ventricular systolic and diastolic pressure occurred with hypoxia, but no significant differences in these pressures were observed between groups. Left ventricular pulse pressure and coronary flow also decreased significantly during hypoxia (both, P < 0.05), but hearts from the proestrous group maintained a significantly higher pulse pressure (P < 0.05). Hearts from the proestrous group also maintained significantly higher rates of coronary flow during hypoxia (P < 0.05), compared with hearts from the diestrous group. However, despite the effect of proestrus, correlation coefficients between plasma estradiol concentrations and indices of cardiac function were not significant.Conclusions: Our findings indicate that the estrous cycle of the female rat affects cardiac function during hypoxia. This model may be useful to study the impact of the estrous cycle on metabolic and cardiovascular function.     

人脐带间充质干细胞移植对糖尿病大鼠血清学的影响

目的:观察人脐带间充质干细胞(hu MSCs)移植对糖尿病大鼠血糖、胰岛素和血清因子表达的影响。方法:随机选择12只Wistar大鼠通过腹腔注射链脲佐菌素50 mg/kg,血糖高于16.7 mmol/L者定为糖尿病大鼠,再将其随机分为糖尿病组和干细胞组,每组6只,同时选择6只雄性Wistar大鼠为正常组。干细胞组大鼠腹腔注射hu MSCs细胞悬液,糖尿病组注射PBS液。分别于注射2周、4周和6周后测定和比较各组大鼠的血糖、血清胰岛素、肿瘤坏死因子(TNF-α)和白介素-6(IL-6)的表达。结果:与正常组比较,糖尿病组和干细胞组大鼠的血糖水平均显著升高,胰岛素水平均显著降低(P0.01)。与糖尿病组比较,干细胞组大鼠注射hu MSCs后的血糖水平明显降低,胰岛素水平明显升高(P0.05),血清TNF-α和IL-6 m RNA水平均显著降低(P0.01)。结论:hu MSCs移植能显著降低糖尿病大鼠的血糖,促进其胰岛素分泌,同时降低血清TNF-α和IL-6的表达。     

Effect of a 20 kHz sawtooth magnetic field exposure on the estrous cycle in mice

Female mice post weaning were exposed to 20 kHz sawtooth electric and magnetic fields (EMF) with 6.25 microT peak intensity for 6 weeks. Estrous cycles were checked using vaginal smears over the last 10 days of the experimental period. The vaginal smears from EMF-exposed mice revealed an increase in the frequency of one or two phases persisting. The number of estrous cycles less than 1 was more in the EMF-exposed group than in the sham control group. Furthermore, in the EMF-exposed group, the duration of proestrous and metestrous stages of the estrous cycle was significantly increased compared with the control group. In conclusion, our results suggest that exposure to 20 kHz sawtooth EMF may affect normal cycling of the estrous cycle by disrupting the female reproductive endocrine physiology. We should not disregard the possible adverse reproductive effect of the 20 kHz sawtooth EMF generated under the occupational exposure situation in females.     

Estradiol-induced adult anovulatory syndrome in female C57BL/6J mice: age-like neuroendocrine, but not ovarian, impairments

Long-term effects of elevated plasma estradiol (E2) on ovarian and neuroendocrine functions were examined in 4-month-old cycling female C57BL/6J mice injected s.c. with 0.2 or 0.05 mg estradiol valerate (EV), or oil. Within 7 days, EV-injected mice became permanently acyclic, exhibiting the persistent vaginal cornification (PVC) characteristic of reproductive senescence in rodents. Four months after injection, ovaries from EV-injected mice exhibited no corpora lutea, but ovulated in response to an injection of human chorionic gonadotropin (hCG) (as do older, spontaneously PVC mice). When grafted into young mice, ovaries from EV-injected mice supported as many estrous cycles as ovaries from oil-injected controls. EV did not alter the suppression of luteinizing hormone (LH) by E2, LH response to injected LH releasing hormone (LHRH), or plasma prolactin (Prl). However, EV-injected mice exhibited impairments in LH regulation similar to those seen in old, acyclic mice. Plasma LH 30 days after ovariectomy was 40% lower, and E2-induced LH surges were 60% lower, in EV-injected mice versus controls. Furthermore, EV-injected mice were unable to support estrous cycles given young ovarian grafts, in contrast to controls. Effects of sustained but physiological levels (15-20 pg/ml) of plasma E2, were examined in intact cycling mice given sham or E2 implants. Six weeks after implantation, the implants were removed; only 50% of the E2-implanted mice subsequently exhibited estrous cycles, compared with 100% of sham-implanted controls. Furthermore, those E2-implanted mice which did cycle had fewer cycles than controls.(ABSTRACT TRUNCATED AT 250 WORDS)