高蛋白食物和繁殖对布氏田鼠能量摄入和产热的影响

为探讨高蛋白食物和繁殖对布氏田鼠食物摄入和产热等特征的效应,将成年雌性布氏田鼠分为非繁殖对照食物组、非繁殖高蛋白组、繁殖对照食物组和繁殖高蛋白组。对照食物蛋白含量为17.7%,高蛋白食物的蛋白含量为36.6%。实验过程中测定动物的体重、食物摄入量、静止代谢率(RMR)、身体成分、内脏器官重量、褐色脂肪组织(BAT)解偶联蛋白1(UCP1)含量、血清瘦素和催乳素水平等。结果发现:高蛋白食物明显抑制布氏田鼠的体重,但动物在妊娠期和哺乳期,这种抑制作用消失。高蛋白食物明显抑制非繁殖组动物的干物质摄入、摄入能和消化能,但对哺乳期动物没有影响。高蛋白食物提高了非繁殖期和繁殖期动物的消化率,降低了血清瘦素浓度,但仅提高了繁殖期动物肾脏的重量,而降低了盲肠的重量。RMR、UCP1含量和血清催乳素浓度等则不受高蛋白食物的影响。繁殖期动物的体重、能量摄入、RMR和血清催乳素浓度等均高于非繁殖动物。这些结果表明,食物蛋白含量可影响布氏田鼠的能量代谢和产热特征等,且在繁殖期和非繁殖期有不同的反应方式。     

池养雄性白鱀豚性自慰行为与血清睾酮浓度之间的关系

自 1996年 3月至 1998年 12月 ,作者采用放射免疫分析法每月 1次测定雄性白豚 (Lipotesvexillifer)“淇淇”血清睾酮浓度。春季每天 1次 ,其它季节每三天 1次 ,每次 1h ,用目标动物取样法观察“淇淇”的行为。结果发现 ,性自慰 (腹面贴池壁、伸出阴茎 )行为的发生频率和血清睾酮激素水平都有周期性变化 ,春季为高峰期 ,秋季有 1个小峰 ,性自慰行为与血清睾酮激素浓度两者的周期较为一致。从性自慰行为和血清睾酮激素水平季节变化 ,推测出“淇淇”性腺活动的周期性变化 ,活动期为 2～ 10月 ,血清睾酮浓度为 2 4 8～ 9 6 6ng/ml;春季高峰在 4月前后 ,血清睾酮浓度为 3 4 4～ 9 6 6ng/ml;秋季小峰在 10月 ,血清睾酮浓度为 3 33～4 2 5ng/ml;11月至次年 1月为性腺活动相对静止期 ,血清睾酮浓度为 1 2 4～ 2 85ng/ml。白豚是一种季节性繁殖动物 ,繁殖高峰期在 4月前后。     

环境温度和繁殖经历对黑线仓鼠哺乳期能量收支的影响

为探讨环境温度和繁殖经历对黑线仓鼠哺乳期能量收支的影响,将连续3次繁殖的黑线仓鼠暴露于温度梯度降低的条件下(30—0℃,1℃/4d),使初次、第2和3次繁殖的动物分别暴露于30—20℃、20—10℃、10—0C℃,测定了哺乳期能量收支。与初次繁殖的动物相比,第3次繁殖组动物的摄食量显著增加,静止代谢率、非颤抖性产热、褐色脂肪组织细胞色素c氧化酶(COX)活性和血清T3水平显著增加,而断乳时胎仔重显著降低。结果表明:(1)低温下繁殖的黑线仓鼠处于负能量平衡,在自身维持和哺育后代的能量分配之间存在权衡,低温下产热增加,繁殖输出减少;(2)黑线仓鼠可能感知环境温度的变化,在连续降低温度的条件下降低繁殖投资,符合"季节性投资假说"的预测。     

黑线毛足鼠妊娠期光照对仔鼠睾丸发育的影响

季节性繁殖动物,其生殖活动的变化具有内在遗传性,但光照作为环境因子对生殖活动的变化进程起重要的调节、整合作用,一年四季光照长度有规律周期性变化,将季节性繁殖动物的生殖活动调定在适当的时期,从而最有利于该种动物的生存与繁衍。光照在调节动物繁殖中,其长度...     

动物对孢子植物的传播模式及进化意义

孢子植物物种多样性丰富, 是自然生态系统的重要组成部分。孢子植物的传播通常被认为主要依靠风、水、弹力等非生物媒介, 而动物的作用往往被忽略。本文主要概述了: (1)孢子植物对动物传播的适应: 一方面孢子植物可为动物提供食物、庇护所、繁殖场所等, 另一方面孢子植物也可产生视觉、嗅觉等方面的线索来吸引动物, 从而促进动物传播其繁殖体。(2)动物对孢子植物的传播模式: 包括体内传播(消化道和组织寄生)和体外传播两种, 这些模式都能对孢子植物繁殖体进行有效传播。由于动物间形态或生活习性的不同, 以致传播距离存在差异, 最短距离为0.1 cm, 最长距离可从北半球至南半球。(3)动物对孢子植物传播的生态与进化意义; 由于某些孢子植物繁殖体的结构特点或萌发的需求, 以致其繁殖体只能通过动物的传播才能得以定殖, 因此动物与孢子植物之间存在密不可分的关系。目前, 动物对孢子植物的传播研究主要是描述性的内容以及研究单方面的传播途径, 建议在今后的研究中考虑动物对孢子植物传播的有效性以及多途径同时传播对孢子植物定殖的影响, 同时应更加关注孢子植物和动物互惠关系的形成、维持机制及将来的进化趋势。     

动物园里小熊猫的饲养与繁殖

小熊猫(Ailurus fulgens)是我国的珍贵动物之一。动物园倒养中不易繁殖。我园1973年引进小熊猫一对(下面分别用♀、♂表示)。1974年7月开始繁殖。五年来繁殖9胎,成活8只,其中第二代繁殖获得成功。经饲养与观     

高体重布氏田鼠产仔数较多但繁殖输出及氧化损伤不受影响

体重可影响动物几乎所有的生物学变量。高体重双亲通常产生较大胎仔数。繁殖过程代价很高,可能伴随着氧化损伤。为比较双亲体重对繁殖期能量学特征、繁殖输出和氧化损伤的影响,检测了高体重组(雌性:51. 5 g ± 1. 6 g;雄性:60. 4 g ±2. 5 g)和低体重组(雌性:35. 5 g ± 1. 2 g;雄性:49. 6 g ± 2. 8 g)布氏田鼠繁殖过程中母体的体重和摄食量,分娩时的胎仔数和胎仔总重,及后代断乳时母体的身体成分、激素含量(血清瘦素和催乳素)和氧化损伤(血清丙二醛、蛋白质羰基和肝脏丙二醛含量)。结果显示:(1)高体重组妊娠末期的母体体重增量显著高于低体重组;(2)高体重组母体的出生胎仔数显著高于低体重组,但出生及断乳时的平均胎仔重、胎仔总重和母体繁殖期间的能量摄入无显著差异; (3)血清激素含量、身体成分、身体脂肪重量及氧化损伤指标均无组间差异。结果表明,高体重布氏田鼠可产生较多的出生胎仔数,但母体并不通过摄入更多的能量来保证其繁殖输出,对氧化损伤也没有影响。这些结果对于理解不同体重的动物在繁殖期间的能量策略以及繁殖与生存之间的权衡等生活史理论具有重要意义。     

阴道毛滴虫的研究 Ⅴ.不同动物血清对牛胎毛滴虫(T.foetus)繁殖率的影响

到目前为止所有培养毛滴鞭毛虫(Trichomonades)的培养基都不能缺少人或动物的血清。Riedmuller氏在1936年首先指出在肉汤加全血的培养基中,血清是促进牛胎毛滴虫在玻皿生长繁殖的主要因素;而经洗涤或是经溶血后的血球就没有这种促进生长的作用。Sprince和Kupferberg 1947年以及Kupferberg,Johnson和Sprince 1948年研究阴道毛滴鞭毛虫(T.vaginalis)的营养要素时发现在人血清中具有两种促进生长的因素:     

池养雄性白Ji豚性自慰行为与血清睾酮浓度之间的关系

自1996年3月至1998年12月,作者采用放射免疫分析法每月1次测定雄性白Ji豚（Lipotes vexillifer)“淇淇”血清睾酮浓度。春季每天1次,其它季节每三天1次,每次1h,用目标动物取样法观察“淇淇”的行为。结果发现,性自慰（腹面贴池壁、伸出阴茎）行为的发生频率和血清睾酮激素水平都有周期性变化,春季为高峰期,秋季有1个小峰,性自慰行为与血清睾酮激素浓度两者的周期较为一致。从性自慰行为和血清睾酮激素水平季节变化,推测出“淇淇”性腺活动的周期性变化,活动期为2－10月,血清睾酮浓度为2．48－9．66ng/ml。春季高峰在4月前后,血清睾酮浓度为3．44－9．66ng/ml;秋季小峰在10月,血清睾酮浓度为3．33－4．25ng/ml;11月至次年1月为性腺活动相对静止期,血清睾酮浓度为1．24－2．85ng/ml。白Ji豚是一种季节性繁殖动物,繁殖高峰期在4月前后。     

中国野生脊椎动物鸣声监测与生物声学研究进展

<正>声音(鸣声)通讯是许多动物类群的重要通讯方式,在动物社群交流和繁殖活动中起着非常重要的作用。采用鸣声通讯的动物类群十分丰富,包括哺乳类、鸟类、两栖爬行类、鱼类和昆虫,这些类群的生境涵盖了陆地、淡水和海洋等各类生态系统。生物声学研究最初以描述动物的声音特征为主,     

蒙药乌力吉-18对大鼠下丘脑-垂体-卵巢轴相关激素及受体表达的影响

目的:探讨蒙药乌力吉-18对大鼠下丘脑-垂体-卵巢轴相关激素及受体的影响。方法:选取40只健康雌性未孕SD大鼠,随机分为空白组、对照组、乌力吉-18高、低2个剂量组,每组10只。空白组灌胃等体积蒸馏水,对照组灌胃逍遥丸,高、低剂量组分别灌胃2.0 g·kg^-1·d^-1、1.0 g·kg^-1·d^-1乌力吉-18,连续给药31学艺术d。采用酶联免疫吸附法测定血清促性腺激素释放激素(GnRH)、促卵泡生成素(FSH)、黄体生成素(LH)、雌二醇(E₂)及孕酮(PROG)的含量;免疫组化法检测下丘脑组织促性腺激素释放激素(GnRH)、垂体组织促性腺激素释放激素受体(GnRHR)的表达;以蛋白免疫印迹技术检测卵巢组织促卵泡生成素受体(FSHR)、黄体生成素受体(LHR)蛋白表达量。以实时荧光定量PCR检测卵巢组织中FSHR、LHR基因表达量。结果:与空白组比较,乌力吉-18低剂量组可明显升高血清LH含量(P<0.05),上调下丘脑组织GnRH、垂体组织GnRHR表达及卵巢组织FSHR、LHR蛋白表达(P<0.05);乌力吉-18高剂量组可显著升高血清FSH、LH、E₂含量(P<0.05),上调下丘脑组织GnRH表达及卵巢组织FSHR表达量(P<0.05),并可显著升高卵巢组织中FSHR、LHR基因表达量(P<0.05);对照组可明显升高血清E₂含量(P<0.05)。结论:蒙药乌力吉-18可明显升高血清FSH、LH及E₂的含量,促进下丘脑组织GnRH、垂体组织GnRHR及卵巢组织中FSHR、LHR的表达,表明乌力吉-18能够对下丘脑-垂体-卵巢轴相关激素及受体表达产生影响。     

Estradiol and progesterone synthesis in human placenta is stimulated by calcitriol

Calcitriol exerts a diverse range of biological actions including the control of growth and cell differentiation, modulation of hormone secretion, and regulation of reproductive function. The placenta synthesizes calcitriol through the expression of CYP27B1, but little is known about local actions of this hormone in the fetoplacental unit. The objective of this study was to investigate the effects of calcitriol upon progesterone (P₄) and estradiol (E₂) secretion in trophoblasts cultured from term human placenta. Cells were incubated in the presence of calcitriol for 18 h and pregnenolone or androstenedione were subsequently added as substrates for the 3β-hydroxysteroid dehydrogenase (3β-HSD) or P450-aromatase (CYP19), respectively. Calcitriol stimulated in a dose-dependant manner E₂ and P₄ secretion. The use of a selective inhibitor of PKA prevented the effects of calcitriol upon E₂ secretion, but not on P₄. These results show that calcitriol is a physiological regulator of placental E₂ and P₄ production and suggest a novel role for calcitriol upon placental steroidogenesis.     

Serum steroid hormones, sex hormone-binding globulin concentrations, and urinary hydroxylated estrogen metabolites in post-menopausal women in relation to daidzein-metabolizing phenotypes

Equol and O-desmethylangolensin (O-DMA) are products of bacterial metabolism of daidzein, an isoflavone in soybeans; thus, the presence or absence of equol and/or O-DMA in urine is a marker of particular intestinal bacteria profiles. Plasma hormone concentrations may be lower in pre-menopausal women who harbor the bacteria capable of producing equol (equol producers) compared to women who do not (equol non-producers). We evaluated concentrations of serum hormones, sex hormone-binding globulin (SHBG), and urinary 2-hydroxyestrone (2-OH E₁) and 16-hydroxyestrone (16-OH E₁) in relation to equol-producer and O-DMA-producer phenotypes in 89 post-menopausal women. Follicle stimulating hormone (FSH) was 23% greater in O-DMA-producers compared to non-producers (P=0.04). No significant differences in serum estrogens, androgens, metabolic hormones, or SHBG were observed in relation to either daidzein-metabolizing phenotype. Compared with non-producers within each phenotype, age-adjusted 2-OH E₁:16-OH E₁ was 27% greater (P=0.06) in equol-producers and 9% greater (P>0.10) in O-DMA-producers, and 2-OH E₁ concentrations were 24% greater in equol producers (P=0.07) and 42% greater in O-DMA producers (P=0.02). No significant differences in 16-OH E₁ were observed in relation to either phenotype. These results suggest that interindividual variability in intestinal bacteria may be related to differences in products of hormone metabolism in post-menopausal women.     

卡贝缩宫素联合Bakri球囊压迫对宫缩乏力性产后出血患者卵巢功能和凝血功能的影响

目的:探讨卡贝缩宫素、Bakri球囊压迫联合治疗对宫缩乏力性产后出血患者卵巢功能以及凝血功能的影响。方法:选取2017年2月-2021年3月我院接诊治疗的86例宫缩乏力性产后出血患者,以随机数字表法分为对照组、研究组,分别给予Bakri球囊压迫单一治疗及卡贝缩宫素、Bakri球囊压迫联合治疗。检测对比患者的卵巢功能指标包括LH、FSH、E2水平,记录两组患者舒张压(DBP)、收缩压(SBP)、心率、出血量变化和止血起效时间,测定纤维蛋白原(FIB)、凝血酶原时间(PT)和活化部分凝血活酶时间(APTT),对比两组不良反应发生情况。结果:两组患者DBP、SBP及心率变化波动较小,治疗后数据显示差异无统计学意义(P>0.05);两组患者治疗后2 h、24 h出血量减少,且研究组治疗后2 h、24 h出血量及止血起效时间短于对照组(P<0.05);治疗后3 d,两组患者FIB水平降低,PT、APPT水平升高,且研究组FIB水平低于对照组,PT、APPT水平高于对照组(P<0.05);治疗后3 d,两组患者血清E₂水平升高,FSH、LH水平降低,且研究组血清E₂、FSH、LH水平优于对照组(P<0.05);研究组不良反应发生率(8.89%)高于对照组(4.88%),但是未见显著性差异(P>0.05)。结论:卡贝缩宫素联合Bakri球囊压迫可改善宫缩乏力性产后出血的卵巢功能及凝血功能,提升产后止血效果,增强患者子宫收缩能力。     

外源褪黑激素对水貂血清主要生殖激素年周期变化的影响

为探究埋植外源褪黑激素（MLT）对水貂血清主要生殖激素年周期变化的影响,实验选用4月龄雌貂和雄貂各72只,分为A、B、C、D组,A组（雌貂）和C组（雄貂）不做任何处理,B组（雌貂）和D组（雄貂）于2018年7月7日至2019年7月7日埋植外源MLT。实验期间,每隔30 d每组随机选取3只水貂,心脏采血并分离血清,共12次。用酶联免疫吸附实验（ELISA）法分别测定雌貂和雄貂血清中主要生殖激素含量。结果表明：（1） A组促性腺激素释放激素（GnRH）、催乳素（PRL）和孕酮（P）除冬季1月处于高水平,其他时间均处于较低水平;夏季在6月出现小高峰,P在7月出现小高峰;促卵泡素（FSH）和促黄体生成素（LH）在秋、冬季先下降后上升且在12月达高水平,春、夏季FSH呈逐渐下降趋势,LH呈先下降后上升趋势;雌二醇（E2）在秋、冬季逐渐上升且在1月达高水平,春、夏季逐渐下降后波动。（2） B组与A组相比较,GnRH分别在10月和1月显著升高（P ≤ 0.05）,且1月极显著升高（P ≤ 0.01）;PRL在1月、2月、6月降低（P ≤ 0.05）;P在10月、6月升高（P ≤ 0.05）,1月降低（P ≤ 0.01）;FSH和LH在10月显著上升（P ≤ 0.05）,且FSH极显著上升（P ≤ 0.01）,但FSH在1-2月降低（P ≤ 0.05）,LH在3月显著上升（P ≤ 0.05）。（3） C组睾酮（T）仅在冬季1月上升至高水平;C组与D组相比较,T仅在1月降低（P ≤ 0.01）。由此得出,外源MLT能使1月GnRH浓度提高,PRL、P、T的浓度降低,使FSH和LH浓度于10月提前达峰值,E2于11月提前达峰值。埋植MLT导致雄性和雌性水貂发情时间不一致,因而此法并不适于种貂繁殖。     

Interactions between FSH, estradiol-17β and transforming growth factor-β regulate growth and differentiation in the rat gonad

Estradiol-17β (E₂) is a mitogen in vivo for the proliferation of granulosa cells in the rat ovary. E₂ is synthesized by the preovulatory follicle through a series of gonadotrophin-dependent events: LH stimulates thecal cells to synthesize androgens (androstenedione and testosterone) which are substrates for FSH-induced aromatization to estrogens in granulosa cells. More recently, we have found that transforming growth factor-β (TGF-β) stimulates DNA synthesis in rat granulosa cells in vitro and this effect is augmented by FSH. Since E₂ is a mitogen in vivo and TGF-β is the only known growth factor to stimulate proliferation in vitro, the possible link between the actions of E₂ and TGF-β were examined. E₂ stimulated the secretion of a TGF-β-like factor by rat granulosa cells in culture, and with time DNA synthesis was stimulated. The mitogenic action of E₂ was enhanced in the presence of FSH, and attenuated by a neutralizing antibody to TGF-β. The latter observations have identified TGF-β as the “missing-link” in the mitogenic actions of E₂ on rat granulosa cells. In addition to the growth-promoting actions of TGF-β plus FSH, TGF-β enhanced FSH-induced aromatase activity. Consequently, FSH plus TGF-β stimulates both the proliferation and aromatization capacity of rat granulosa cells. We propose that interactions between FSH, E₂ and TGF-β lead to the exponential increase in serum E₂ levels that occurs during the follicular phase of the cycle. Similarly, FSH stimulates the aromatization of exogenous androgens to estrogen by Sertoli cells isolated from immature rat testes, and there is a correlation between FSH-induced aromatization and mitotic activity. We have shown that FSH plus TGF-β stimulates DNA synthesis in Sertoli cells. Since E₂ increases the secretion of TGF-β by Sertoli cells, interactions between FSH, E₂ and TGF-β may provide the mitogenic stimulus for Sertoli cells during the prepubertal period. In summary, our findings suggest that the estrogen-induced growth of rat granulosa cells is mediated through the production of TGF-β, which acts as an autocrine regulator of proliferation. We also propose that the growth-promoting actions of FSH on Sertoli cells may depend upon a cascade series of events involving estrogens and TGF-β.     

Effects of an antagonist of neurokinin receptors 1, 2 and 3 on reproductive hormones in male beagle dogs

BACKGROUND: SCH 206272, a neurokinin 1, 2, and 3 receptor antagonist, administered to beagle dogs results in testicular toxicity. Therefore, a series of experiments were conducted to determine whether this observed toxicity was associated with changes in reproductive hormones and hypothalamic gonadotrophin releasing hormone (GnRH) levels. METHODS: Male beagle dogs were administered 30 mg/kg SCH 206272 for up to 7 days. Blood samples were collected at the end of the dosing period for reproductive hormone analysis. Male reproductive organs were stained with hematoxylin and eosin and the hypothalamus was stained for GnRH. RESULTS: Intact male dogs exhibited SCH 206272‐related decreases in pulsatility and magnitude of luteinizing hormone (LH) and testosterone, which were associated with seminiferous tubule degeneration, oligospermia, and epithelial atrophy in the prostate gland. Neutered dogs also exhibited SCH 206272‐related decreases in LH and FSH. In a subsequent reversibility study, intact male dogs exhibited decreased LH, testosterone, and FSH, which exhibited recovery by 2 weeks post‐dosing; however, seminiferous tubule degeneration and oligospermia did not exhibit recovery by 2 weeks post‐dosing. Dogs administered SCH 206272 also exhibited an increase in mean number of GnRH‐containing neurons in the hypothalamus and an increase in GnRH mRNA/neuron, which exhibited recovery by 2 weeks post‐dosing. CONCLUSIONS: SCH 206272‐dosed dogs exhibited rapid decreases in reproductive hormones and subsequent testicular pathology. Collectively, these changes in hormone levels suggest that the observed SCH 206272‐related reproductive tract findings are the result of alterations in hypothalamic–pituitary–gonadal function. However, a direct effect on the testes cannot be definitively ruled out. Birth Defects Res (Part B) 89:517–525, 2010. © 2010 Wiley‐Liss, Inc.     

赤腹松鼠血清肝肾功能指标的测定

以捕自四川荥经县的161只成体赤腹松鼠(Callosciurus erythraeus,雄鼠76只,雌鼠85只)为研究对象,从2015年2月至12月分四个季节测定了雌、雄鼠血清中反映肝肾功能的14项指标,并分析了妊娠对各项指标的影响。结果显示:(1)肝肾功能指标均无显著的性别差异。(2)白蛋白、胆碱酯酶和肌酐在春季有升高的趋势,但无明显的季节差异。(3)总蛋白、球蛋白及尿酸含量春季低于其他季节,总胆红素、直接胆红素、间接胆红素和尿素氮含量春季高于其他季节,前白蛋白、丙氨酸氨基转移酶、天冬氨酸氨基转移酶和γ-谷氨酰转移酶春季高于其他季节,夏季显著下降,冬季最低。(4)妊娠鼠血清胆碱酯酶含量高于未妊娠鼠,尿素氮、肌酐和尿酸含量低于未妊娠鼠。结果表明,雌、雄赤腹松鼠肝肾功能指标无性别差异且季节变化趋势相同,大多数在春季变化显著且妊娠影响较小,这可能与雌、雄的繁殖状态及在多变性环境条件下的生理适应能力有关。     

Effects of 9-ene-tetrahydrocannabinol on expression of β-type transforming growth factors, insulin-like growth factor-I and c-myc genes in the mouse uterus

Effects of cannabinoid on expression of β-type transforming growth factors (TGF-β1, -β2 and -β3), insulin-like growth factor-I (IGF-I) and c-myc genes in the uteri of adult ovariectomized mice were examined using Northern blot hybridization. Mice were exposed to 9-ene-tetrahydrocannabinol (THC) alone or in combination with an injection of estradiol-17β (E₂) and/or progesterone (P₄), and uteri were analyzed at various times thereafter. TGF-β isoform messenger RNAs (mRNAs) persisted in ovariectomized uteri and their levels were not altered after THC treatment, whereas an injection of E₂ caused a modest increase in TGF-β1 and -β3 mRNA levels at 24 h. Imposition of THC treatment advanced the stimulatory effects of E₂ by changing the timing for the peak of TGF-β3 mRNA levels to 12 h. In comparison, E₂ treatment substantially elevated the levels of TGF-β2 mRNA at 6 h, and THC potentiated this E₂ response without affecting the timing for the response. Imposition of P₄ treatment did not antagonize any of these responses. P₄ treatment alone or with THC had insignificant effects on mRNA levels for these TGF-β isoforms. Uterine levels of IGF-I and c-myc mRNAs were low in ovariectomized mice and THC did not alter these mRNA levels. In contrast, E₂ treatment induced a rapid, but transient, increase in IGF-I and c-myc mRNAs, and THC antagonized the rapid c-myc mRNA response and altered the timing of the IGF-I mRNA response. P₄ treatment alone also caused the transient induction of these mRNAs, but THC failed to antagonize these effects. An injection of P₄ plus E₂ resulted in further modest increases in IGF-I and c-myc mRNA levels as compared to E₂ or P₄ treatment alone. However, THC did not antagonize these transient stimulatory effects of the combined ovarian steroids. The data suggest that THC should not be classified as estrogenic or antiestrogenic. However, this compound can modulate (potentiate, antagonize and/or alter timing) the effects of ovarian steroids on uterine gene expression.