肾上腺素能受体平衡与肺血管通透性关系的研究

本实验动态地检测了油酸所致大鼠肺血管通透性增高的发生、发展过程中肺组织中α、β肾上腺素能受体(αAR、βAR)的最大结合容量及亲和力的变化。结果发现:实验组大鼠肺组织中αAR与βAR之间的平衡遭到了破坏,αAR显著增多,而βAR却显著减少。应用αAR阻断剂——酚妥拉明或βAR激动剂——舒喘灵均可有效地防治油酸引起的大鼠肺血管通透性增高,使肺系数明显减小,支气管肺泡灌洗液中蛋白质含量明显减少,肺组织病变明显减轻。实验结果提示:肾上腺素能受体在肺微血管通透性的调控过程中可能起着重要的作用;肺组织中αAR与βAR之间的平衡失调可能是肺血管通透性增高的重要原因;纠正这种失衡是防治通透性肺水肿的有效手段。     

孕酮膜受体在小鼠生殖系统的分布与表达

目的观察孕酮膜受体(membrane progestin receptors,m PRs)在小鼠子宫、输卵管和卵巢的分布及其周期性变化。方法用实时定量PCR、免疫组织化学分别检测动情期和动情间期小鼠生殖系统m PRs的m RNA及蛋白表达。结果在子宫内,m PRα、β免疫阳性反应分布于内膜上皮、腺体上皮、内膜基质和血管内皮,而m PRγ弱免疫阳性反应见于腺体上皮和血管内皮;在卵巢中,m PRα、β免疫阳性反应见于卵巢间质、卵母细胞和颗粒细胞,m PRγ而未见明显免疫阳性反应;在输卵管中,3种蛋白均未见明显免疫阳性反应。实时定量PCR显示3种m RNA在卵巢、输卵管和子宫均表达,m PRβ的m RNA表达水平最高;动情期和动情间期3种m RNA在卵巢、输卵管和子宫中均有表达,而表达水平无显著性差异。结论 m PRα、β在卵巢和子宫中表达稳定,提示小鼠生殖系统中,孕酮的非基因效应可能更多依赖m PRα、m PRβ的介导,尤其是m PRβ。     

长期糖尿病大鼠心脏肾上腺素受体及其介导的功能的变化

目的:探讨长期糖尿病大鼠心脏肾上腺素受体(AR)的改变及其与心功能变化之间的关系.方法:采用链脲佐菌素(STZ)注射造成胰岛素依赖性糖尿病大鼠模型,放射配体结合实验和离体左心房收缩功能实验等方法观察心脏AR及功能的改变.结果:与同龄对照大鼠相比,糖尿病大鼠心脏β-AR的最大结合容量(Bmax)下降34%(P<0.05),KD值不变;心脏α1-AR Bmax无显著改变.糖尿病大鼠左心房β-AR介导的最大收缩反应(Rmax)较对照组下降64%(P<0.05);α1-AR介导的最大收缩反应增加36%(P<0.05),pD2值不变.结论:长期糖尿病大鼠心脏β-AR介导的最大收缩反应降低,其可能与β-AR数量减少有关.α1-AR介导的最大收缩反应代偿性增强,其可能与受体后信号转导效应增强有关.     

缺氧大鼠心肌α1,β肾上腺素能受体的变化

为了探讨α_1、β肾上腺素能受体在大鼠缺氧性心脏肥大进程中的作用,本研究应用放射配基结合法观察了不同缺氧时间大鼠心室α_1、β肾上腺素能受体变化的动态过程,同时也观察了α_1、β受体阻断剂在预防缺氧性心肌肥大发生中的作用。缺氧10d后,测定右心室重量及组织学检查未见右心室肥大,但此时心室肌α_1受体数量从对照组的27.49±1.25增加到33.80±0.90fmol/mg蛋白(P<0.05);β受体从对照组的51.80±7.60下降到25.10±2.30fmol/mg蛋白(P<0.01)。缺氧20和30d后α_1受体进一步增加到40.70±1.43和32.30±1.96fmol/mg蛋白(P<0.05);β受体分别为27.90±2.30和42.80±1.70fmol/mg蛋白(P<0.05)。缺氧20和30d后右心室重量指数明显高于对照组,在整个缺氧过程中α_1、β受体的亲和性(K_d)未见明显变化,未见左心室肥大。缺氧同时应用α_1受体阻断剂(哌唑嗪4mg·kg~(-1)·d~(-1))30d,可明显预防缺氧所致的右心肥大;而β受体阻断剂(心得安10mg·kg~(-1)·d~(-1))没有此种作用。由此可见,在缺氧所致右心肥大之前,心肌α_1受体数量即明显升高,α_1受体阻断剂可以预防缺氧引起的右心肥大。     

心脏β肾上腺素受体及其亚型随年龄而变化

本文采用放射配体结合实验和离体左心房收缩功能观察了４８周期和１０周龄Ｗｉｓｔａｒ大鼠心脏β肾上腺素受体（β－ＡＲ）及其亚型的数量和功能的改变。结果表明：（１）心脏β－ＡＲ总数量在４８周龄大鼠较１０周龄大鼠下调约２８％,且为β１与β２－ＡＲ同等程度下调;（２）４８周龄大鼠β－ＡＲ及其亚型对异丙肾上腺素的敏感性明显减弱;（３）在１０周龄大鼠心脏介导收缩效应以β１－ＡＲ的作用为主,而在４８周龄大鼠心脏引     

一种新的具有多肽性质的β-肾上腺素能受体阻滞剂

从蚯蚓中分离得到的能够抑制离体豚鼠心耳收缩的活性成分,经放射性配体结合实验表明,能够抑制~8H标记的心得舒与鸭红细胞膜制剂内β—肾上腺素能受体的结合。在腺苷酸环化酶活性测定中能抑制异丙基肾上腺素对酶的激活作用。为一种新的内源性的β—肾上腺素能受体阻滞剂。     

肾上腺素能神经不参与由电场刺激所诱发的豚鼠回肠纵肌的抑制效应

本实验在离体的豚鼠回肠肌间神经丛一纵肌上进行。实验表明,10Hz 电场刺激产生的抑制效应与刺激时间相关非常显著。此抑制效应可被阿片受体阻断剂纳洛酮拮抗。α-肾上腺素能受体阻断剂酚妥拉明,β-肾上腺素能受体阻断剂心得安及去甲肾上腺素的膜摄取抑制剂可卡因均不能显著地改变此抑制效应。化学切割剂6-羟多巴胺损毁纵肌标本内肾上腺素能神经末梢后,该抑制效应无明显变化,且仍可被纳洛酮所拮抗。这些结果说明,肾上腺素能神经可能不参与由10Hz 电场刺激所诱发的抑制效应。     

肝纤维化肝组织中肾上腺素能受体的表达研究

目的探讨肝纤维化大鼠肝脏组织中交感神经递质受体表达的变化情况。方法应用四氯化碳(CCl4)诱导大鼠慢性肝纤维化模型。23只Wistar大鼠随机分为正常对照组(N组)和肝纤维化模型组(M组)。应用逆转录聚合酶链反应(RT-PCR)和Westernblot方法检测肝脏组织中肾上腺素能受体mRNA及蛋白质的表达情况。结果肝纤维化大鼠肝脏组织中肾上腺素能受体mRNA和蛋白质表达均比正常组明显增加(P<0·01)。结论肝纤维化时,大鼠肝脏组织中肾上腺素能受体α1-AR和β2-AR表达增加,这可能是肝纤维化时交感神经促进肝纤维化发展的作用机制之一。     

大鼠子宫游离酪氨酸与孕激素受体含量的关系

本文用高效液谱方法,检测了正常成年大鼠子宫内膜胞浆中游离酪氨酸(Tyr)含量,发现其浓度随动情周期的不同而发生波动,在动情前期最低,动情后期最高。同时检测了子宫内膜胞浆中孕激素受体(PR)含量的变化,以动情前期最高,动情后期最低。同样呈有规律的变化。表明酪氨酸与孕激素受体含量在子宫内膜胞浆中浓度的变化呈负相关,实验进一步证实,当向子宫腔内局部注射酪氨酸时,酪氨酸明显减少动情前期、动情期、间情期大鼠子宫内膜胞浆孕激素受体含量,但对动情后期孕激素受体含量无显著影响,这些结果提示酪氨酸可能影响孕激素受体的含量。     

高血压糖尿病大鼠心脏肾上腺素受体的改变与心功能变化之间的关系

目的:研究高血压糖尿病大鼠心脏肾上腺素受体(AR)的改变与心功能变化之间的关系.方法:采用左肾动脉缩窄和注射链脲佐菌素制高血压糖尿病大鼠模型,放射配体结合实验和离体左心房收缩功能实验等方法观察心脏AR(β-AR和/或α1-AR)及功能的改变.结果:与正常对照相比,高血压糖尿病大鼠心脏β-AR的最大结合容量(Bmax)增加35%(P＜0.01),KD值不变;且心脏α1-AR的Bmax也显著增加(P＜0.05).高血压糖尿病大鼠左心房与对照相比,β-AR介导的最大收缩反应(Rmax)下降48%(P＜0.01),pD2值不变;α1-AR介导的最大收缩反应也降低41%(P＜0.05),pD2值不变.结论:高血压糖尿病大鼠心脏β-AR和/或α1-AR数量代偿性增加,但其介导的最大收缩反应降低,可能与受体后信号转导效应减弱有关.     

Spontaneous and oxytocin-induced uterine motility in cyclic and postpartum mares

Intrauterine pressure was measured in three cyclic and two postpartum mares. Pressure was recorded using a catheter tip pressure transducer. The transducer was passed transcervically into the uterus.. In cyclic mares recordings were started on Day 1 of estrus and continued daily until ovulation as well as on Days 1 and 8 of diestrus. In postpartum mares recordings were started within 48 h after foaling and continued until the mares ovulated. The intrauterine pressure changes in postpartum mares was also recorded on Days 1 and 8 of diestrus. Spontaneous uterine contractions were recorded in cyclic mares for 30 min and in postpartum mares for 10 min. Induced uterine motilities were recorded for 30 min in both groups after the administration of oxytocin (40 USP, i.v.). Total area under the contraction curve in a 10-min period was used as a uterine motility quantitating unit. All mares demonstrated uterine contractions during estrus and diestrus. All mares demonstrated significant responses to oxytocin during estrus and diestrus. It appears that estrogen priming is not necessary for a significant uterine response to oxytocin.     

Maturation of spontaneous and agonist-induced uterine contractions in the peripartum mouse uterus.

This study tested the hypothesis that the uterus achieves maximum contractile capabilities before the onset of labor. Basal and agonist-stimulated contractions were assessed in uterine strips on Day 15 or 18 of pregnancy, the day of parturition, or 1 day postpartum (n = 4-13 per group). Spontaneous contractions were evident in all groups (n = 4-13 per gestational group); contraction frequency was greater in peripartum groups than in virgin controls ( approximately 4.6 versus 2.8/200 sec). Peak amplitude was nearly 9-fold higher on Days 15 and 18 and over 30-fold higher in the postpartum and 1 day postpartum groups than in nonpregnant mice. Maximum frequency and peak amplitude were achieved in response to 10(-6) to 10(-8) M oxytocin or arginine vasopressin (OT(max) or AVP(max)). Frequency of contractions in response to OT(max) peaked on Day 18 and then declined. Contraction amplitude increased 5-fold on Day 15, declined on the day of birth (equivalent to nonpregnant level), then rebounded to peak on postpartum Day 1. AVP(max) similarly increased frequency and amplitude of contractions, except that maximum contraction amplitude occurred postpartum. Thus, an endogenous oscillator, residing in the uterus, sustains high basal and agonist-induced contraction frequency during pregnancy. Although acceleration of this pacemaker occurred before term, the data suggest that peripartum increases in contraction amplitude characterize the transition to the powerful synchronous contractions of parturition.     

Acute effects of a single ethanol injection on in vitro rat uterine spontaneous motility, on uteri prostaglandin production and on tissue metabolism of triglycerides.

The acute effects of ethanol (ETOH), injected at 3 g.kg-1i.p. on spontaneous contractions, on prostaglandin (PG) production and on the metabolism of triglycerides (TGs), have been studied in uterine strips obtained from rats at diestrus and suspended in glucose-containing or glucose-free solution. The absolute values of isometric developed tension (IDT: expressed in mg) recorded at 0 time (initial or post isolation determinations) and the frequency of contraction (FC), expressed as the number of contraction cycles during 20 min, were similar for uterine strips from controls and from ETOH treated rats. The uterine IDT and the FC expressed as percent changes from internal controls (0 time values) were explored during 180 min in uteri suspended in glucose medium. The magnitude of IDT decreased, as time progressed, both in controls as well as in ETOH-treated rats. Afterwards, uterine strips from controls exhibited a partial recovery of their contractile activity. This pattern of recovery was not observed in uterine strips from ETOH-treated rats. The uterine IDT, in the ETOH-injected animals after 180 min of activity, were significantly smaller than those of controls. On the other hand, the FC decreased progressively up to the end of the experimental period both in controls as well as in ETOH-treated rats. In glucose-free medium, the IDT of uterine strips from ETOH-injected animals diminished significantly more than controls from 100-180 min following isolation and mounting. In addition, the FC of uterine strips from the ETOH group of rats were significantly smaller than in controls suspended in glucose-free solution.(ABSTRACT TRUNCATED AT 250 WORDS)     

Uterine oxytocin receptors in cyclic and pregnant cows.

Binding of [3H]oxytocin to uterine subcellular preparations ('oxytocin receptor concentrations') was measured in uterine tissue of heifers and multiparous dairy cows at various stages of the oestrous cycle and during early pregnancy. A method for the assay of ovine uterine oxytocin receptors was optimized for use on bovine tissue. Oxytocin receptor concentrations were increased in cyclic animals around the period of luteolysis and oestrus, rising on Day 15 in endometrium and on Day 17 in myometrium while pregnant animals showed no comparable rise. Receptor concentrations then declined on Day 3 after oestrus in myometrium and on Day 5 in endometrium. Some cyclic animals did not show the expected rise in receptors in the late luteal phase; these animals had abnormally high progesterone concentrations for this stage of the cycle. In animals slaughtered on Day 18 after oestrus and/or insemination which had low oxytocin receptor levels, plasma progesterone concentrations were consistently high; while all animals showing the late luteal phase elevation in receptor values had low progesterone concentrations. Oxytocin receptor and progesterone concentrations were negatively correlated (P less than 0.05). These data support the hypothesis that oxytocin receptor level is a key factor in the process of luteolysis in cattle and that in pregnancy there is suppression of uterine oxytocin receptor at the expected time of luteolysis. We suggest that uterine oxytocin receptor levels are partly controlled by circulating steroid hormones and are suppressed during early pregnancy.     

Electromyographic activity of the uterus in the ewe during the sexual season: comparison of natural estrus and estrus induced by progestagens alone or with PMSG supplementation

Electromyographic (EMG) activity of the uterus was recorded in vivo in 3 groups of ewes in oestrus during the breeding season. The ewes were either in natural oestrus or in oestrus induced by progestagens with or without PMSG supplementation. Plasma concentrations of LH were measured at regular intervals in order to determine the onset of the preovulatory surge of LH (To). During natural oestrus, the uterus exhibited a spontaneous rhythmic activity composed of bursts of potentials. Burst frequency was maximal at the moment of preovulatory LH release, then decreased. Percentages of downward, upward and non-definite propagations were calculated during 1-h periods at the beginning of the LH peak and 6, 12, 24 and 36 h afterwards. There was no difference between the relative proportions of these types of propagation at any of the times analysed. Mean burst frequency was not modified by progestagen pre-treatment but showed more interanimal variability at the moment of maximal frequency in ewes treated with progestagen. For the first 12 h after To, the organization of uterine activity was not modified by progestagens but non-definite propagation became predominant 24 and 36 h after To, namely from the time of ovulation onward. PMSG increased burst frequency. The increase of frequency variability between animals, normally observed at the beginning of oestrus, and the predominance of non-definite propagation, normally observed at the end of progestagen-induced oestrus, did not appear when the ewes had been treated with PMSG.     

Seasonal changes in the effects of arginine vasotocin and stretch on Anolis uterine contractions in vitro

We determined the effects of acute stretch on spontaneous and arginine vasotocin (AVT)-driven contractions of the Anolis carolinensis uterus in vitro. Whole uteri from reproductively inactive females (October) were placed in a bath of oxygenated 32 degrees C Anolis "Ringer's." Two initial tensions were utilized, 1.5 g or 15 g, the latter being an estimate of the tension on the wall of a uterine compartment. Uteri were then exposed to either saline or AVT (50 ng/ml), and spontaneous or AVT-driven contractions were recorded for 20 min with the use of a strain gauge and physiograph. A similar experiment was performed on uteri from reproductively active females in the summer (June). Our results indicate that the effects of acute stretch and AVT on uterine contractility were qualitatively similar in summer and fall. That is, AVT induced a tonic contraction; stretch decreased the duration of the tonic contraction; the saline-treated uteri exhibited spontaneous rhythmic contractions; AVT increased the amplitude of the rhythmic contractions, but only at the lower tension; there were no effects of AVT on the timing (contraction interval, duration, rest interval) of the rhythmic contractions; and stretch increased the frequency of the rhythmic contractions. Season greatly influenced the magnitude of these contractile phenomena. Uteri tested during the breeding season exhibited greater distensibility, an increase in the amplitude and duration of the AVT-driven tonic contraction, and an increase in the frequency of both spontaneous and AVT-driven rhythmic contractions because of a decrease in both contraction duration and rest interval.(ABSTRACT TRUNCATED AT 250 WORDS)     

Adrenergic influence of uterine muscle contractions stimulated by a glycoside from the root of Dalbergia saxatilis

The mechanism of uterine muscle contraction stimulated by a triterpenoid glycoside (dalsaxin) isolated from the root of D. saxatilis was investigated by in vitro methods in the rat. Dalsaxin caused a dose-related increase in uterine muscle contraction. The contraction was single and transient and was abolished by moderate doses of isoprenaline (1.80 nmol-0.40 mumol) and salbutamol (0.13-25 mumol). Adrenaline (9.10 nmol) also caused a reversible decrease (92.6%; P < 0.01) in myometrial contraction stimulated by this glycoside (0.24 mg/ml). Uterine muscle responses to dalsaxin (0.24 mg/ml) were enhanced by the beta-adrenergic receptor antagonist, propranolol, in a dose related manner. Atipamezole (1.50 ng/ml) but not prazosin (7.72 nmol-15.60 nmol) substantially reduced (80%; P < 0.01) myometrial contractions induced by this uterine spasmogen. The results suggest that dalsaxin enhances uterine muscle contraction by stimulating post junctional alpha 2-adrenergic receptors, presumably by inhibiting plasma membrane adenylate cyclase system and its associated increase in intracellular cAMP content.     

Adaptation of uterine artery thick- and thin-filament regulatory pathways to pregnancy

Little is known about the adaptation of uterine artery smooth muscle contractile mechanisms to pregnancy. The present study tested the hypothesis that pregnancy differentially regulates thick- and thin-filament regulatory pathways in uterine arteries. Isometric tension, intracellular free Ca(2+) concentration, and phosphorylation of 20-kDa myosin light chain (MLC(20)) were measured simultaneously in uterine arteries isolated from nonpregnant and near-term (140 days gestation) pregnant sheep. Phenylephrine-mediated intracellular free Ca(2+) concentration, MLC(20) phosphorylation, and contraction tension were significantly increased in uterine arteries of pregnant compared with nonpregnant animals. In contrast, phenylephrine-mediated Ca(2+) sensitivity of MLC(20) phosphorylation was decreased in the uterine arteries of pregnant sheep. Simultaneous measurement of phenylephrine-stimulated tension and MLC(20) phosphorylation in the same tissue indicated a decrease in MLC(20) phosphorylation-independent contractions in the uterine arteries of pregnant sheep. In addition, activation of PKC produced significantly lower sustained contractions in uterine arteries of pregnant compared with nonpregnant animals in the absence of changes in MLC(20) phosphorylation levels in either vessels. In uterine arteries of nonpregnant sheep, the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase inhibitor PD-098059 significantly increased phenylephrine-mediated, MLC(20) phosphorylation-independent contractions. The results suggest that in uterine arteries, pregnancy upregulates alpha(1)-adrenoceptor-mediated Ca(2+) mobilization and MLC(20) phosphorylation. In contrast, pregnancy downregulates the Ca(2+) sensitivity of myofilaments, which is mediated by both thick- and thin-filament pathways.     

Protein phosphorylation during spontaneous contraction of smooth muscle

The relationship between spontaneous contraction and protein phosphorylation of rat uterine smooth muscle was studied. Myometrial strips from estrogen-dominated rats were incubated in [³²P]orthophosphate and then frozen at various levels of isometric tension. Proteins were separated by gel electrophoresis and the incorporation of ³²P was measured. Contraction was associated with the phosphorylation of one major protein (20,000 M_r). This phosphorylation preceded maximal tension development and dephosphorylation preceded complete spontaneous relaxation. Two-dimensional gel electrophoresis indicates that the 20,000-M_r protein is the myosin light chain which has been implicated in the regulation of smooth muscle contraction.     

The differential effects of tamoxifen and ICI 182,780 on the reduction of Na+/K+ ATPase activity and spontaneous oscillations by 17beta-estradiol

A prolonged treatment with 17beta-estradiol reduces the frequency of spontaneous oscillations and the Na+/K+ ATPase activity in rat uteri. Acute inhibition of Na+/K+ ATPase activity by a Na+/K+ ATPase inhibitor, ouabain, decreases the frequency of oxytocin-induced oscillations in uteri. Therefore, the purpose of this study was to examine whether the prolonged inhibition of Na+/K+ ATPase activity by 17beta-estradiol was estrogen receptor (ER)-dependent. The uterine explants from ovariectomized rats were cultured in vitro as our experimental model to compare the effect of two antiestrogenic compounds (ICI 182,780 and tamoxifen) on the Na+/K+ ATPase activity and the frequency of spontaneous oscillations. ATPase assay and a standard muscle bath apparatus were to measure the activity and the contraction. When compared with the control, a 2-day treatment with 17beta-estradiol in vivo or in vitro decreased the activity and the frequency. ICI 182,780 lowered the activity but tamoxifen did not. ICI 182,780 did not decrease the frequency but tamoxifen did. Even the reversal effects of these antiestrogenic compounds on the reduced activity and the frequency by 17beta-estradiol were different. Tamoxifen elicited a greater reversal effect on the reduced activity but ICI 182,780 did not. In contrast, ICI 182,780 elicited a greater reversal effect on the reduced frequency but tamoxifen did not. Prolonged inhibition of Na+/K+ ATPase activity by K+-free solution suppressed the frequency with the elevation of basal tension. Addition of KCl at lower concentrations (0.3-1.2 mM) induced oscillatory contraction after reducing the basal tension. As our data suggest, the prolonged effect of 17beta-estradiol may decrease uterine the activity through ER dependent and independent pathways. The reduction of uterine Na+/K+ ATPase activity by estrogens may increase the basal tension after each oscillatory cycle, which, in part, contributes to the reduced frequency of spontaneous oscillations.