齐墩果酸对氟伐他汀在大鼠体内药动学的影响

目的 探讨齐墩果酸对氟伐他汀在大鼠体内的药代动力学影响。方法 将16只健康大鼠随机分为单药组(5.0mg?kg-1 氟伐他汀)和联合用药组(5.0mg?kg-1氟伐他汀 60mg?kg-1 齐墩果酸),单药组和联合用药组分别灌胃空白溶剂和齐墩果酸5天,每天一次。第6天两组均给予氟伐他汀灌胃,给药后不同时间点采血,LC-MS法测定大鼠体内血药浓度,比较两组间主要的药代动力学参数。结果 与单药组比较,联合用药组氟伐他汀主要药代动力学参数Cmax、AUC0-t参数值显著上升,组间比较差异具有统计学意义(P＜0.05)。结论 联合应用齐墩果酸可能影响大鼠体内氟伐他汀的药代动力学特性。     

甲磺酸帕珠沙星与其它抗生素联用于大鼠模型的药动学研究

目的:对甲磺酸帕珠沙星与其它抗生素联合应用的大鼠药代动力学进行对比研究,评价药物间的相互作用及联合用药的合理性.方法:采用一个剂量组,3种用药方案分别单次给药.用药方案:帕珠沙星45 mg/kg;帕珠沙星45 mg/kg加头孢哌酮/舒巴坦180 mg/kg;帕珠沙星45 mg/kg加阿奇霉素45 mg/kg.采用反相HPLC-UV法测定大鼠血药浓度,用DAS软件估算药动学参数,进行统计学分析及临床药效评价.结果:甲磺酸帕珠沙星单用及与头孢哌酮/舒巴坦或阿奇霉素联用的主要药动学参数t1/2、Cmax、tmax、AUC无显著性差异,但帕珠沙星与阿奇霉素联用后清除率(CL)降低及体内驻留时间(MRT)延长,具有统计学意义.结论:帕珠沙星与头孢哌酮/舒巴坦,帕珠沙星与阿奇霉素联用是可行的用药方案.     

银杏叶提取物对吡拉西坦在大鼠体内药代动力学的影响

目的：探讨银杏叶提取物单次给药和多次给药对吡拉西坦在大鼠体内药代动力学的影响。方法：选用雄性SD大鼠18只,随机分为空白对照组(n=6)、银杏叶提取物单次干预组(n=6)和银杏叶提取物多次干预组(n=6),银杏叶提取物灌胃后,给予吡拉西坦尾静脉注射50 mg·kg^-1,后采集血样测定大鼠血浆中吡拉西坦的浓度。采用DAS计算各组药代动力学参数,并进行统计学分析。结果：与空白对照组相比,多次给予银杏叶提取物后,吡拉西坦的AUC减少了60%,MRT降低了50%,T_1/2z减少了47%,Cl升高了154%(P<0.05)。结论：银杏叶提取物多次干预会使吡拉西坦在大鼠体内的血浆暴露显著减少,并显著加快药物在体内的消除速率。临床上吡拉西坦与银杏叶提取物合用时,需考虑药物之间的相互作用。     

七叶皂苷对洛伐他汀在高脂血症大鼠模型体内药代动力学的影响

目的在高脂血症大鼠模型中研究七叶皂苷对洛伐他汀药代动力学的影响。方法采用高脂饲料喂饲大鼠,构建高脂血症大鼠模型,通过血清生化分析确定造模成功。选择12只造模成功的大鼠,随机分成2组,即单独给药组和联合给药组,每组6只大鼠。单独给药组和联合给药组大鼠分别经尾静脉注射给予0.9%生理盐水和注射用七叶皂苷钠(0.5 mg/kg,qd),连续14 d。第14天,给药后,两组大鼠灌胃给予洛伐他汀(20 mg/kg,0.5%CMC-Na溶液),并于洛伐他汀给药前和给药后不同时间点采集血样,采用HPLC-MS/MS方法测定洛伐他汀及其活性代谢物洛伐他汀酸的血药浓度,计算药动学参数。结果长期给予七叶皂苷钠导致洛伐他汀酸的血浆暴露水平显著升高,Cmax、AUC0-t、AUC0-∞分别是单独给药组的2.43(90%CI:1.55,3.31)、2.66(90%CI:1.67,3.66)和2.99倍(90%CI:1.44,4.55),两组比较差异有统计学意义(P<0.05)。与单独给药组相比,联合给药组洛伐他汀的血浆暴露也略有增加,但两组Cmax和AUC比较差异无统计学意义(P>0.05)。结论七叶皂苷可抑制高脂血症模型大鼠的洛伐他汀代谢,增加其体内暴露水平。     

华法林和阿司匹林联用在大鼠体内的药代动力学研究(英文)

目的:探讨华法林和阿司匹林联用在大鼠体内非稳态和稳态条件下的药代动力学相互作用的规律,为临床合理药物联用提供依据。方法:将大鼠随机分为3组,即华法林组(0.2mg/kg),阿司匹林组(10mg/kg),华法林(0.2mg/kg)+阿司匹林组(10mg/kg)联用组,每组6只,给大鼠灌胃,连续6d,在第1天和第6天多个时间点取样,分析和比较非稳态和稳态下血药浓度时间曲线和药代动力学参数。结果:华法林药动学用二室模型描述,阿司匹林药动学用一室模型描述。在非稳态和稳态下,阿司匹林单用和联用的血药浓度-时间曲线相似,药代动力学参数之间均无统计学差异;在非稳态下,华法林单用和联用的血药浓度-时间曲线也类似,但在稳态下,联用的血药浓度时间曲线明显高于单用时的曲线,药代动力学计算结果也表明联用时的AUC和Cmax较单用时较大,且有统计意义。结论:当华法林和阿司匹林联用达到稳态时,阿司匹林对华法林的药动学参数有影响,增大了华法林的暴露(AUC和Cmax)。提示两药联用时,很可能增大患者的出血风险,临床上药物联用时应该注意。     

测定莫西沙星和利福布汀联合给药后大鼠的血药浓度及其药动学变化

目的:建立测定大鼠血浆中莫西沙星和利福布汀浓度的HPLC法,并分别研究莫西沙星和利福布汀单独及联合灌胃给药后,大鼠血浆中两药的药动学.方法:血浆样品采用甲醇沉淀蛋白,莫西沙星采用HPLC-UV法测定,利福布汀采用HPLC-MS法测定.18只大鼠随机分为3组:莫西沙星(40 mg/kg)和利福布汀(30 mg/kg)单独给药组,以及莫西沙星(40mg/kg)和利福布汀(30 mg/kg)联合给药组,比较联合给药后两种药品的药动学与单独给药时的差异.结果:莫西沙星和利福布汀浓度在0.05～5、0.15～ 30 μg/ml线性关系良好(r=0.999 9);最低定量限分别为0.05和0.15 μg/ml;两药提取回收率及日内、日间RSD均符合方法学测定要求.与各自单独给药相比,联合给药时莫西沙星AUC0～1AUC0～∞显著升高(P＜0.05),清除率显著降低(P＜0.05);利福布汀AUC0-t、AUC0-∞显著升高(P＜0.05),表观分布容积(Vd)、清除率显著降低(P＜0.05).结论:本研究建立的两药血药浓度测定方法简单、准确、可靠,适用于莫西沙星与利福布汀药动学研究.与单独给药时相比,莫西沙星和利福布汀联合给药后两药的清除率降低,生物利用度增加,在体内具有协同作用.     

酮康唑对奥拉西坦在大鼠体内药代动力学的影响

目的建立测定大鼠血浆中奥拉西坦含量的高效液相色谱法,研究酮康唑对奥拉西坦在大鼠体内药代动力学的影响。方法色谱柱为DiamonsilRPC18柱(250mm×4.6mm,5μm),流动相为乙腈-水(3.2:96.8),流速为0.8mL/min,检测波长210nm,柱温40℃,进样量20μL。试验组大鼠连续灌胃给予酮康唑(50mg/kg,每日1次)7d后,单次灌胃给予奥拉西坦(200mg/kg),测定奥拉西坦血药浓度,计算药代动力学参数,并与单次灌胃给予奥拉西坦(200mg/kg)的对照组进行比较。结果奥拉西坦标准曲线方程为Y=0.0217X+0.1058(r=0.9992,n=7),质量浓度线性范围为2～100mg/L;低、中、高3种质量浓度的方法回收率分别为(102.25±8.51)%,(96.29±2.76)%和(98.14±1.62)%,日内及日间精密度的RSD均小于5.42%。对照组与试验组主要药代动力学参数,半衰期(t1/2)分别为(2.807±0.8751)h和(3.231±1.019)h,峰浓度(Cmax)分别为(52.80±16.94)mg/L和(47.33±8.317)mg/L,0～12h药时曲线下面积(AUC0-12h)分别为(257.2±77.84)mg.h/L和(258.9±67.30)mg.h/L,组间比较无显著性差异。结论酮康唑对大鼠体内奥拉西坦的药代动力学无显著影响。     

银杏叶提取物与阿托伐他汀联合应用对大鼠CYP450蛋白水平的影响

目的观察银杏叶提取物与阿托伐他汀联合应用对大鼠CYP450蛋白水平的影响。方法将24只SD大鼠随机分为生理盐水(NS)组、阿托伐他汀(AV-T)组、银杏叶提取物(GBE)组、GBE联合AV-T组,每组6只。NS组用生理盐水1 m L/(kg·d)灌胃,AV-T组1 mg/(kg·d)AV-T灌胃,GBE组50 mg/(kg·d)GBE灌胃,GBE联合AV-T组GBE 50 mg/(kg·d)联合AV-T 1 mg/(kg·d)灌胃。6周后,取大鼠肝脏,制备肝微粒体,CO-还原差示光谱法检测肝微粒体CYP450酶含量;Western blot检测肝脏组织中CYP3A4和CYP2C9蛋白的表达。结果与NS组及AV-T组相比,GBE组、GBE+AV-T组CYP450酶含量明显升高(P<0.01)。与NS组及AV-T组相比,GBE组、GBE+AV-T组CYP3A4的表达显著降低(P<0.01,P<0.05);GBE组、GBE+AV-T组CYP2C9的表达显著上升(P均<0.01)。结论 GBE与AV-T联合应用后,使大鼠肝微粒体CYP450含量增高,且影响CYP3A4和CYP2C9的蛋白表达,由此可能会影响AV-T的疗效。     

稳态时难治性癫痫大鼠体内脑心清对卡马西平药动学及脑组织分布的影响

目的 研究难治性癫痫大鼠体内稳态时脑心清对卡马西平药动学及脑组织分布的影响。方法 采用脑立体定位技术向SD大鼠侧脑室内注入红藻氨酸（KA）建立难治性癫痫模型,造模成功后,将难治性癫痫模型大鼠随机分为卡马西平组和脑心清+卡马西平组,卡马西平组给予卡马西平80 mg/kg及生理盐水5 ml灌胃,脑心清+卡马西平组给予脑心清550 mg/kg+卡马西平80 mg/kg灌胃,连续给药60 d。在不同时间点采集血样及脑组织样品,测定血浆与脑组织中卡马西平的浓度,计算药动学参数并进行统计学分析。结果 与单用卡马西平组相比,脑心清联合卡马西平组的药动学参数差异无统计学意义;而脑心清联合卡马西平组的脑药浓度明显高于单用卡马西平组。结论 长期给药脑心清不影响卡马西平在难治性癫痫大鼠体内的稳态血药浓度,且对卡马西平通过血脑屏障具有一定的促进作用,提高了卡马西平的稳态脑药浓度。     

氯沙坦及其代谢物在维吾尔族和汉族健康志愿者的药代动力学

目的 研究维吾尔族和汉族健康受试者单剂量口服氯沙坦钾片(抗高血压药)的药代动力学特征.方法 20名健康受试者(其中维吾尔族10名,汉族10名,男女各半),单剂量口服氯沙坦钾片50 mg;用高效液相色谱-荧光法测定氯沙坦及其代谢物E-3174血药浓度,用DAS软件进行数据处理、SPSS 13.0软件进行统计学分析.结果 维吾尔族受试者单剂量口服氯沙坦钾片50 mg后氯沙坦和代谢物E-3174的主要药代动力学参数分别为:Cmax(344±153),(477±166)μg·mL-1;tmax(1.0±0.3),(2.6±0.5)h;t1/2(1.0±0.4),(2.9±0.8)h;AUG0-24h(598±216),(2243±518)μg·h·mL-1;AUC0-∞(632±242),(2429±552)μg.h·mL-1.汉族受试者单剂量口服氯沙坦钾片50 mg后氯沙坦和代谢物E-3174的主要药代动力学参数分别为:Cmax(351±168),(242±60)ng·mL-1;tmax(1.4±1.1),(3.6±1.7)h;t1/2(0.8±0.4),(4.7±1.1)h;AUC0-24h(497±172),(1853±194)ng·h·mL-1;AUC0-∞(523±184),(1960±182)ng·h·mL-1.结论 氯沙坦的代谢物E-3174的药代动力学参数t1/2、Vd、Cmax在维吾尔族和汉族健康受试者间的差异有显著性意义(P＜0.05),不同性别间药代动力学参数的差异无显著性意义(P＞0.05),所有药代动力学参数在同一民族和不同民族的个体间差异都很大,临床治疗中应实行个体化给药方案.     

银杏叶提取物对肝纤维化模型大鼠的影响及抗肝纤维化机制的研究

目的 探讨银杏叶提取物(GBE)对肝纤维化模型大鼠的影响及抗肝纤维化机制.方法 SD大鼠60只随机分为正常组(n=12)和模型组(n=48),模型组大鼠又分为4个亚组:模型对照组、GBE低、中、高剂量组(n=12),GBE低、中、高剂量组每天分别灌胃给予GBE 50mg/kg、100mg/kg及200mg/kg,正常组和模型组给予等体积的0.9%氯化钠溶液,连续2个月(1次/d).给药结束后腹主动脉取血,分离血清,试剂盒检测肝功能指标(ALT、AST、MDA、SOD、白蛋白、球蛋白及白/球),放免法检测肝纤维化指标(HA、PC-Ⅲ、C-Ⅳ及LN),大鼠脱颈椎处死后立即取右叶部分肝组织,液氮速冻后于-80℃保存,RT-PCR检测肝组织TGF-β1、TIMP1、Ⅰ型胶原mRNA的表达水平.结果 与模型对照组比较,GBE中、高剂量组AST、ALT、球蛋白及肝纤维化各项指标显著降低,TGF-β1、TIMP1、Ⅰ型胶原mR-NA表达水平显著降低(P<0.05),白蛋白水平、白/球值显著升高(P<0.05),MDA水平差异无统计学意义(P>0.05).结论 GBE能显著改善肝纤维化大鼠的肝功能指标,肝纤维化指标,其机制可能是通过降低TGF-β1、TIMP1、Ⅰ型胶原mRNA表达水平来实现的.     

Herb–drug interactions: Effect of Ginkgo biloba extract on the pharmacokinetics of theophylline in rats

Herbal medicines have received great attention as alternative medicines in recent years and are also referred to as a dietary supplement or health food. Ginkgo biloba extract (GBE) is one of the most popular herbal medicines. However, little is known about the metabolic interactions between GBE and clinically used drugs. This study attempted to investigate the effect of GBE on the pharmacokinetics of theophylline, a cytochrome P450 (CYP) 1A2 substrate and an important therapeutic agent with narrow therapeutic window used for the treatment of asthma.

Commercial GBE (10 or 100 mg/kg, p.o.) or water (control group) was given to rats (6 rats for each group) for 5 consecutive days and on the sixth day theophylline (10 mg/kg) was administered either orally or intravenously. The results showed that pretreatment of rats with GBE resulted in an increase in the total clearance of theophylline of about 30% (GBE 10 mg/kg, P < 0.05) and 70% (GBE 100 mg/kg, P < 0.01) compared with the control group after intravenous administration of theophylline (10 mg/kg). After oral administration of theophylline (10 mg/kg), the AUC_0–24 h of theophylline was reduced by 40% following pretreatment with GBE (100 mg/kg, P < 0.01). These results demonstrate that GBE pretreatment increased CYP1A2 metabolic activity and the clearance of theophylline in rats.     

Effects of ginkgo biloba on <Emphasis Type="Italic">in vitro</Emphasis> osteoblast cells and ovariectomized rat osteoclast cells

Ginkgo biloba extract (GBE) has a selective estrogen receptor modulator (SERM)-like biphasic effect on estrogen, and could be a potential alternative to hormone replacement therapy (HRT). Here, we investigated whether GBE can ameliorate estrogen-depleted osteoporosis in in vitro osteoblast cells and in estrogen-deprived ovariectomized (OVX) rats, a classical animal model for postmenopausal osteoporosis. GBE (50–150 μg/mL) significantly increased ALP (Alkaline phosphatase) activity of osteoblast cells, indicating that GBE promotes osteoblast mineralization. OVX rats exposed to GBE (100 and 200 mg/kg/day, oral treatment), raloxifene (3 mg/kg/day, oral treatment) or estradiol (E₂, 10 μg/kg/day, subcutaneous injection) decreased osteoclast resorptive activity compared with OVX rats. GBE and raloxifene did not increase uterine weight compared with OVX rats, while E₂ and Sham control did, suggesting that GBE has no uterotrophic activity, which is a disadvantage of estrogen therapy. In OVX rats, GBE did not restore severe bone density loss induced by OVX, indicating that GBE may be insufficient as therapeutic material for severe osteoporosis. However, despite its no effects on bone density loss in OVX rats, GBE did stimulate osteoblast differentiation and antiosteoclastic activity in vitro. Therefore, GBE may have preventive potential on osteoporosis as do other phytoestrogens.     

Studies on interactions between functional foods or dietary supplements and medicines. III. Effects of ginkgo biloba leaf extract on the pharmacokinetics of nifedipine in rats

The effects of Ginkgo biloba leaf extract (GBE), one of the most widely used herbal dietary supplements in Japan and the United States, on the pharmacokinetics of nifedipine (NFP), a typical probe of P450 (CYP) 3A, but not a substrate of the multidrug transporter P-glycoprotein (P-gp), were studied using rats. Simultaneous oral treatment with GBE (20 mg/kg) did not affect the pharmacokinetics after intravenous administration of NFP (2.5 mg/kg). However, the maximal plasma NFP concentration, the area under the concentration-time curve and absolute bioavailability after oral administration of NFP (5 mg/kg) were significantly increased by simultaneous oral treatment with GBE, approximately 1.6-fold, 1.6-fold and 2.1-fold, respectively. These results suggest that the concomitant oral use of GBE appeared to reduce the first-pass metabolism of orally administered NFP, by inhibiting CYP3A, possibly but not P-gp, in rats.     

Ginkgo biloba extract markedly induces pentoxyresorufin O-dealkylase activity in rats

We examined the effect of Ginkgo biloba extract (GBE) on hepatic drug-metabolizing enzymes, particularly cytochrome P450 (CYP), in rats. Rats were fed a GBE-containing diet or received GBE by intragastric gavage. The concentration of CYP and activity of various CYP enzymes in the liver were increased in a dose- and time-dependent manner. Significant increases in the concentration and activities of CYP enzymes were detected on day 1 of feeding of a 0.5% GBE diet and after administration of 10 mg GBE/kg body weight for 5 days by intragastric gavage. Among the CYP enzymes, the activity of pentoxyresorufin O-dealkylase (PROD), a CYP2B enzyme, was especially markedly increased. The induction of CYP2B enzyme by GBE was confirmed by Western blot analysis. Addition of GBE to a CYP assay system in vitro caused concentration-dependent inhibition of various CYP enzyme activities. The inhibition was more marked for the microsomal enzymes from GBE-treated rats than for those from control rats and more marked against PROD activity among the CYP enzymes tested. When the inhibition of various CYP enzymes activities by GBE in vitro was compared, no marked difference was observed between rat and human hepatic microsomal enzymes. These results indicate that excess intake of GBE induces CYP enzymes, particularly PROD, and may modify the efficacy of drugs taken simultaneously.     

银杏叶提取物抗热性惊厥作用的探究

目的研究不同剂量的银杏叶提取物抗热性惊厥作用。方法取昆明种小鼠32只,随机分为生理盐水组（A组）,30mg／kg银杏叶提取物（GBE）组（B组）,50mg／kgGBE组（C组）,70mg／kgGBE组（D组）。采用热水浴建立小鼠热性惊厥模型,四组小鼠均于腹腔注射．30min后进行热性惊厥模型的建立。分别记录小鼠惊厥潜伏期、惊厥持续时间、小鼠惊厥数和死亡数。结果所有小鼠经过热水浴后均不同程度地发生惊厥反应,A、D组出现个别小鼠死亡。与A组比较．B组小鼠潜伏期和持续时间差异无统计学意义（P〉0．05）,但C、D组都可以显著延长小鼠的惊厥潜伏期,缩短惊厥持续时间,差异均有统计学意义（P〈0．05）。结论银杏叶提取物具有抗热性惊厥作用,并且在50mg／kg剂量下,银杏叶提取物的抗热性惊厥作用较好。     

Effects of Ginkgo biloba on corticosterone stress responses after inescapable shock exposure in the rat

Extracts from the leaves of the Ginkgo biloba tree (GBE) are found to be clinically effective in neuroprotection, cerebral and cardiovascular function and cognitive processing. Recent animal findings suggest that GBE also may improve stress adaptation and prevent learned helplessness, as evidenced by its reduction of behavioral acquisition deficits of active avoidance after inescapable shock exposure. In the present report, the effects of two doses of GBE were studied on corticosterone stress responses and acquisition of active avoidance after inescapable shock exposure. Forty-eight rats were divided into three groups: either receiving a daily dose of 50 mg/kg or 150 mg/kg of GBE (containing 24% flavonoid and 6% terpenoid) or vehicle for 2 weeks. After 2 weeks of administration, animals were trained for active-avoidance acquisition following inescapable shock exposure (stress induction) or nonshock exposure (nonstress). Administration of 150 mg/kg but not of 50 mg/kg of GBE significantly prevented a corticosterone stress response after inescapable shock exposure (P<.0001) without any beneficial behavioral effect on active avoidance. Repeated administration of GBE particularly improves biological adaptation to noxious stimuli without beneficial behavioral consequences. Present findings do not support previous claims about the benefits of G. biloba on improving behavioral stress adaptation and acquisition of active avoidance and on reducing behavioral deficits indicative of "learned helplessness."     

Effect of Ginkgo biloba extract on microsomal enzyme induction

Twenty-four healthy volunteers were divided in three groups who were randomly assigned different treatments for 13 days: group I received 400 mg/day of a defined Ginkgo biloba extract (GBE), group II 300 mg/day of phenytoin and group III a placebo. The elimination half-life of antipyrine was measured with a high performance liquid chromatographic technique initially and on the last day of the administration of the treatments. The results show that the half-life of antipyrine was not affected by GBE and placebo treatments, whereas it was significantly decreased (p less than 0.05) frm 12.2 to 6.8 h after phenytoin control treatment. This study demonstrates that GBE has no effect on the hepatic microsomal drug oxidation system.     

Teratological Evaluation of Orthophenylphenol in Rats

Teratological Evaluation of Orthophenylphenol in Rats. John,J.A., Murray, F.J., Rao, K.S. and Schwetz, B.A. (1981). Fundam.Appl. Toxicol. 1:282–285. Orthophenylphenol (OPP), anantimicrobial used as a chemical disinfectant and for post-harvestpreservation of fruits and vegetables, was evaluated for embryotoxicand teratogenic potential in rats. Pregnant Sprague-Dawley ratswere administered 0, 100, 300, or 700 mg/kg/day of OPP by gavageon gestation days 6 through 15. Evidence of maternal toxicitywas observed among animals given 700 mg OPP/kg/day; pregnantrats in this group weighed less than controls during the periodof dosage and gained less weight as compared to controls duringthe first four days of treatment. Increases in the incidencesof two minor skeletal variants were the only effects observedamong fetuses from rats given 700 mg/kg/day of OPP. No adverseeffects on embryonal or fetal development were observed amonglitters from rats given 100 or 300 mg OPP/kg/day. Orthophenylphenolwas not embryotoxic or teratogenic in rats at dose levels upto 700 mg/kg/day.     

Effect of atrazine on implantation and early pregnancy in 4 strains of rats.

Atrazine (ATR) is an herbicide that has been shown to have adverse reproductive effects including alterations in levels of pituitary hormones such as prolactin (prl) and luteinizing hormone (LH) in female LE rats when administered at doses of 200 mg/kg/day for 1 and 3 days. Because the action of prl in promotion of progesterone secretion is essential for the initiation of pregnancy in rats, this study was designed to examine the effect of exposure to ATR during early pregnancy on implantation and short-term pregnancy maintenance. Rats were divided into two groups representing periods of dosing with ATR prior to the diurnal or nocturnal surges of prl. Within each group, four groups consisting of four strains of rats [Holtzman (HLZ); Sprague Dawley (SD); Long Evans (LE); Fischer 344 (F344)] were each further subdivided into four ATR dosages. Rats were dosed by gavage with 0, 50, 100, or 200 mg/kg/day ATR on days 1-8 of pregnancy (day 0 = sperm +). All animals were necropsied on day 8 or 9 of pregnancy. The 200 mg/kg dose of ATR reduced body weight gain in all but one group. Two groups of animals dosed at 100 and 200 mg/kg/day in the nocturnal dosing period showed an increase in percent preimplantation loss, and both of these were F344 rats. HLZ rats were the only strain to show a significant level of postimplantation loss and a decrease in serum progesterone at 200 mg/kg/day both following diurnal and nocturnal dosing. Doses of 100 mg/kg/day also produced postimplantation loss following diurnal and nocturnal dosing, but progesterone levels were decreased only after nocturnal dosing. Alterations in serum LH were seen in several groups. Serum estradiol was significantly increased only in SD rats dosed at the diurnal interval with 200 mg/kg ATR. We conclude that F344 rats are most susceptible to preimplantation effects of ATR and that HLZ rats appear most sensitive to the postimplantation effects of the chemical. LE and SD rats were least sensitive to effects of ATR during very early pregnancy.