STUDIES ON THE VASODILATOR ACTIONS OF BUCINDOLOL IN THE RAT

Experiments were performed in anaesthetized rats to investigate the vasodilator actions of the beta-adrenoceptor antagonist bucindolol. Bucindolol (3 mg/kg) lowered blood pressure significantly in rats pretreated with (i) prazosin (0.4 mg/kg) (ii) prazosin (0.4 mg/kg) plus propranolol (0.5 mg/kg) or (iii) labetalol (0.5 mg/kg). Thus, a portion of the hypotensive effect of bucindolol was independent of effects on alpha- or beta-adrenoceptors. This was attributed to direct vasodilatation. In reserpinized anaesthetized rats bucindolol increased heart rate and thus had an intrinsic sympathomimetic action (ISA). The ISA was equipotent with that of isoprenaline at the 0.25 nmol/kg dose level, but declined with increasing bucindolol doses, probably due to the onset of beta-adrenoceptor blockade. An isolated perfused rat tail arteries constricted by perfusing with a high-K+ Krebs solution, bucindolol (10(-5) mol/l, 10(-4) mol/l) caused a significant reduction in perfusion pressure indicative of vasodilatation. Since the perfusate contained 10(-6) mol/l propranolol, the vasodilatation was not due to beta-adrenoceptor stimulation. These results are consistent with a direct vasodilator action of bucindolol. We suggest bucindolol lowers blood pressure by a complex mechanism involving beta-adrenoceptor blockade, alpha-adrenoceptor blockade, vasodilatation and perhaps beta 2-adrenoceptor stimulation.     

SOD模拟化合物的研究进展

超氧化物歧化酶 (ｓｕｐｅｒｏｘｉｄｅｄｉｓｍｕｔａｓｅ ,ＳＯＤ) ,是生物体内普遍存在的一种金属蛋白酶 ,按国际标准命名为ＥＣ 1.15 .1.1。它在血浆中的半衰期仅 5～ 8ｍｉｎ ,其保存的稳定性 ,与生物膜的亲和性 ,病灶趋向性及抗原性等问题均是临床应用的难点[1] 。为此用化学手段合成与表征具有相关结构铜、锰、铁甚至钴等金属离子的配合物来模拟ＳＯＤ[2～ 14 ] ,将为进一步认识ＳＯＤ的结构与功能的相关规律性和开发研制新型ＳＯＤ制剂 ,提供重要的理论依据。　　通过Ｘ 射线衍射分析、红外光谱、核磁共振谱、顺磁共振谱、穆斯堡尔…     

EFFECTS OF FREE RADICAL PRODUCTION AND SCAVENGERS ON OCCLUSION–REPERFUSION INDUCED ARRHYTHMIAS

Ventricular arrhythmias were studied in rat isolated hearts subjected to coronary artery occlusion and reperfusion. Free radicals in the perfusate were detected by continuous flow luminol-enhanced chemiluminescence. Administration of purine (2.3 mM) and xanthine oxidase (0.12 U ml⁻¹min⁻¹) did not significantly modify the severity of reperfusion- induced arrhythmias but did generate free radicals. No free radical generation was detected during the period of coronary artery occlusion or reperfusion. Superoxide dismutase (SOD) 20–80 U ml⁻¹did not alter the severity of reperfusion arrhythmias but, in the presence of 80 U ml⁻¹SOD, occlusion-induced arrhythmias were augmented. SOD did not produce any effect on haemodynamics at the concentrations tested. Ventricular arrhythmias and cardiac haemodynamics were also not significantly changed by the combination of scavengers, SOD (10 U ml⁻¹), catalase (100 U ml⁻¹) and mannitol (20 mM). These data suggest that the superoxide free radical is unlikely to be the primary cause of reperfusion induced arrhythmias in rat isolated hearts subjected to regional ischaemia.     

RAT OSTEOGENIC SARCOMA CELLS: MODULATION OF HORMONE STIMULATED CYCLIC AMP PRODUCTION BY PROSTAGLANDIN ANTAGONISTS AND BIOSYNTHESIS INHIBITORS

1. The effects of several anti-prostaglandin drugs on parathyroid hormone (PTH) and prostaglandin E₂ (PGE₂) stimulated cyclic AMP production in freshly isolated rat osteogenic sarcoma cells have been studied. 2. PG biosynthesis inhibitors (aspirin and indomethacin) did not inhibit the effect of PTH and arachidonic acid did not enhance PTH responsiveness. 3. The PG antagonists (SC-19220, phloretin phosphate polymers, 7-oxa-13-prostynoic acid) all inhibited PGE₂-stimulated c-AMP production whilst only the phloretin phosphate polymers at high concentrations inhibited the PTH effect. 4. The data suggest that the primary action of PTH and PGE₂ on these bone-derived cells is independent and that a PG is not involved in the initial events in PTH action.     

FURTHER STUDIES ON THE EFFECT OF ADENOSINE CYCLIC MONOPHOSPHATE DERIVATIVES ON CELL PROLIFERATION IN THE JEJUNAL CRYPTS OF RAT

1. Cell proliferation in the jejunal crypt epithelium of rat was measured using a stathmokinetic technique. 2. Sodium butyrate was found to promote jejunal crypt cell proliferation. 3. N6, O2'-Dibutyryl cyclic adenosine monophosphate (cAMP), N6-monobutyryl-cAMP and N6-monobutyryl-8-bromo-cAMP were found to inhibit cell proliferation when compared to sodium butyrate treated tissues. 4. 8-Chlorophenylthio-cAMP was found to inhibit cell division when compared to untreated animals. 5. O2'-Monobutyryl cAMP and 8-bromo-cAMP were not found to inhibit cell proliferation.     

FURTHER STUDIES ON THE EFFECTS OF ADRENAL STEROIDS IN THE ACTIVE TRANSPORT OF SEROTONIN INTO RAT PLATELETS

Male rats were treated with a fixed dose of aminoglutethimide (50 mg/kg s.c.) or with progressively increasing doses (50-100 mg/kg s.c.) for 3 days. Corticosterone levels were found to be decreased in the latter group. Platelet uptake of serotonin as well as the apparent Vmax were decreased, whereas the Km of uptake were increased when compared with that of the control group. Addition of ACTH (10 iu/dl) to control rat platelet and corticosterone (10-80 micrograms/dl) or triamcinolone (0.5-5.0 micrograms/dl) to adrenalectomized rat platelet suspension in vitro did not increase the serotonin uptake of the preparation. Administration of exogenous dexamethasone (0.05-0.2 mg/kg i.m.) or triamcinolone (0.05-5.0 mg/kg i.m.) to adrenalectomized rats, caused a dose related increase in active uptake of serotonin by the platelets. Deoxycorticosterone (0.1-1.0 mg/kg i.m.) did not have this effect. The time course of response to, and the maximum percentage increase in platelet serotonin uptake by, exogenous corticosteroids are related to their glucocorticoid potency. The possible role of glucocorticoids on platelet serotonin uptake process is discussed.     

香烟依赖与血浆LPO含量及红细胞SOD活性关系的研究

检测经配对设计的５７例吸烟者和５７例健康非吸烟者的血浆过氧化脂质（Ｐ－ＬＰＯ）含量以及红细胞超氧化物歧化酶活性（Ｅ－ＳＯＤＡ）的结果表明，与健康非吸烟组比较．吸烟组的Ｐ－ＬＰＯ平均含量显著升高（Ｐ＜０．００１）、Ｅ—ＳＯＤＡ平均值显著降低（Ｐ＜０．００１），吸烟者的Ｐ－ＬＰＯ含量随吸烟者吸烟史和吸烟量的增加而升高、Ｅ－ＳＯＤＡ值随吸烟者吸烟史和吸烟量的增加而降低，并均呈线性相关（Ｐ＜０．００１）；提示吸烟者体内的氧自由基反应及脂质过氧化反应明显加剧。     

EFFECTS OF OCHRATOXIN A ON CYTOTOXICITY AND CELL DIFFERENTIATION IN CULTURED RAT EMBRYONIC CELLS

In the present study, the effects of ochratoxin A (OTA) on cytotoxicity, cell differentiation, and other cell functions in the embryonic midbrain cells, which are dopaminergic, were compared to those in the limb bud cells, which are nondopaminergic, to assess the selectivity of OTA central action. Twelve-day rat embryo midbrain and limb bud cells were cultured in Dulbecco's modified Eagle's medium nutrient and Ham's F12 (1:1) mixture containing 10% Nuserum for 96 h in the presence of various concentrations of OTA. OTA significantly reduced the levels of protein, DNA and glutathione, and [3H]thymidine incorporation into DNA in both embryonic midbrain and limb bud cells in a similar concentration-dependent manner. The IC50 values for cytotoxicity measured by neutral red uptake were 1.10 µ M in the midbrain cells and 1.05 µ M in the limb bud cells. The IC50 values of cell differentiation were 1.10 µ M in the midbrain cells and 1.0 µM in the limb bud cells. The addition of exogenous glutathione (32.5 µ M) did not change the OTA-induced fall in protein and DNA levels, or the IC50 values of cytotoxicity and differentiation in the midbrain and limb bud cells. Data show that OTA does not appear to exert a selective toxic dopaminergic cell action and that OTA-induced cytotoxicity and inhibition of cell differentiation were not prevented by exogenous glutathione.     

抗痫灵在大鼠肝脏中代谢的研究

用离体大鼠肝脏灌流法,研究了抗痫灵在肝脏灌流过程中的代谢规律。用高效液相色谱法由灌流液中分离、制备得到了两种代谢物,经紫外吸收光谱与质谱鉴定,确定代谢物的结构为3,4-次甲基二氧桂皮酰羟基哌啶及阿魏酰哌啶,后者经化学合成得到了进一步的确证。本文还研究了肝循环过程中抗痫灵的代谢动力学,揭示了大部份抗痫灵以原形结合贮存于肝脏中。     

抗痫灵在大鼠肝脏中代谢的研究

用离体大鼠肝脏灌流法,研究了抗痫灵在肝脏灌流过程中的代谢规律。用高效液相色谱法由灌流液中分离、制备得到了两种代谢物,经紫外吸收光谱与质谱鉴定,确定代谢物的结构为3,4-次甲基二氧桂皮酰羟基哌啶及阿魏酰哌啶,后者经化学合成得到了进一步的确证。本文还研究了肝循环过程中抗痫灵的代谢动力学,揭示了大部份抗痫灵以原形结合贮存于肝脏中。     

应用离心淘洗技术研究VP对PYM细胞毒性的影响

应用最新细胞同步化方法——离心淘洗技术,同步分离体外培养小鼠红白血病细胞(MELC),研究钙拮抗剂异博定(Verapamil:VP)对国产抗癌药物平阳霉素(Pingyangmycin:PYM)细胞毒性的影响。无毒剂量的VP使PYM对未同步化的MELC细胞的毒性加强;同步化后,VP的加入使PYM对G2M期细胞的毒性增强,而对G1期和S期细胞的毒性无明显改变。结果提示,VP与PYM的作用可能有相同的周期特异性。     

CHOLIC ACID AND THE HEART: IN VITRO STUDIES OF THE EFFECT ON HEART RATE AND MYOCARDIAL CONTRACTILITY IN THE RAT

1. Cholic acid has a dose-dependent negative chronotropic effect on isolated atria ofWistar rats. 2. The positive inotropic effect of cholic acid is the result of a negative chronotropic effect and can be eliminated by electrical pacing. 3. Cholic acid does not appear to exert its negative chronotropic effect through cholinoceptors and alterations in bath concentrations of calcium and potassium does not influence this effect significantly. 4. Cholic acid is a functional antagonist of isoprenaline. 5. It is suggested that cholic acid exerts its negative chronotropic effect by forming a monolayer on the surface of the cell membrane, thereby mechanically interfering with membrane function.     

STUDIES ON THE BIPHASIC RELAXANT CURVE OF GLYCERYLTRINITRATE IN RAT AORTA: ROLE OF GTN METABOLITES

1. The present study has examined the possibility that one or more metabolites of glyceryl trinitrate (GTN) (i.e. glyceryl-1,2- and -1,3-dinitrate and glyceryl-1- and -2-mononitrate) may be responsible for the second phase of the biphasic relaxant curve to GTN in phenylephrine-contracted rings of rat aorta. 2. The IC50 values for the two phases of the GTN curve were 0.1 mumol/L and 12 mumols/L with the initial phase eliciting 60% of the total relaxation response. The curves for glyceryl-1,2- and -1,3-dinitrate were monophasic with IC50 values of 248 mumols/L and 110 mumols/L, respectively. The mononitrate metabolites elicited relaxant effects at concentrations greater than or equal to 1 mmol/L. 3. The induction of tolerance to GTN or pretreatment with oxyhaemoglobin (5 mumol/L) resulted in a monophasic GTN curve with IC50 values of 16 mumol/L and 18 mumol/L respectively suggesting selective abolition of responses to low concentrations of GTN with little effect on responses to high concentrations of GTN. The relaxant effects of the -1,2- and -1,3-dinitrates, like that to GTN, were essentially unaltered by GTN tolerance or oxyhaemoglobin. 4. Thus while the relaxant effects of the dinitrate metabolites possess similar properties to that of the second phase of relaxation to GTN, a role for these metabolites is unlikely since their IC50 values are 9-20-fold greater than that for the second phase of relaxation to GTN. Whether these differences are due to the 8-10-fold lower lipophilicity of the dinitrates as compared with the parent compound requires further study.     

THE USE OF THE RAT RIGHT VENTRICLE STRIP IN STUDIES ON NORADRENERGIC TRANSMISSION

• 1 The possibility of using contractility studies with the rat right ventricle strip to assess the effects of drugs on all aspects of noradrenergic transmission has been examined.
• 2 The force of the contractile responses to field stimulation at 0.5 and 2, but not 5 Hz, markedly decreased with time. About 55% of the tissues responded directly to (?)-isoprenaline, 1 × 10^?6M (123 tissues from 220 tested) in the absence of other stimuli. In these tissues the force of the contractile responses remained constant and the rate increased with time. Thus it is essential to provide time controls in studies with rat right ventricle.
• 3 Under conditions in which the responses to (?)-isoprenaline, 1 × 10^?6M, alone were unaffected the responses to field stimulation at 5 Hz were inhibited by 66 and 86% by 9 × 10^?6M tetrodotoxin and 1 × 10^?5M guanethidine, respectively. (+)-Propranolol and timolol (both at 1 × 10^?6M), but not phentolamine, 1 × 10^?6M, inhibited responses to (?)-isoprenaline, 1 × 10^?6M alone and responses to field stimulation at 5 Hz. This demonstrates that the responses to field stimulation are largely due to activation of noradrenergic nerves, the released noradrenaline acting at postsynaptic β-adrenoreceptors.
• 4 Although nortriptyline is a potent inhibitor of the neuronal uptake of noradrenaline, at 1 × 10^?6M it had no effect on the contractile responses to field stimulation at 5 Hz and inhibited responses to (?)-isoprenaline, 1 × 10^?6M, alone and at a higher concentration (1 × 10^?5M) nortriptyline abolished both responses. It is suggested that the rat right ventricle preparation may be useful in examining the effects of drugs on noradrenergic transmission in the heart.

     

STUDIES ON INTERACTION OF TIMOLOL, HYDROCHLOROTHIAZIDE AND AMILORIDE IN THE RAT

1. The acute effects of hydrochlorothiazide, amiloride, timolol and their combinations on diuresis and arterial pressure were studied in rats. 2. Timolol did not modify the diuretic and saluretic effects of hydrochlorothiazide and/or amiloride and had no diuretic or antidiuretic effects alone. 3. At a single dose of 1 25 mg/kg, p.o., timolol alone had no antihypertensive effect in spontaneously hypertensive rats. 4. The antihypertensive effect of hydrochlorothiazide + amiloride+timolol was significantly greater than with any of the drugs alone.     

PROTECTIVE EFFECTS OF LEONURINE IN NEONATAL RAT HYPOXIC CARDIOMYOCYTES AND RAT INFARCTED HEART

• 1 Previous studies have shown that extracts of Herba leonuri, predominantly containing the phytochemical components leonurine and stachydrine, provide protective effects in the ischaemic myocardium by acting as free radical scavengers and inhibiting the formation of reactive oxygen species.
• 2 The present study was designed to investigate the cardioprotective effects of 10^?6 mol/L leonurine on neonatal rat cardiomyocytes treated with hypoxia plus serum deprivation, a component of ischaemia, and to determine the mechanisms underlying the protective effects with regard to cardiac anti‐oxidant enzymes and apoptosis genes. Cardiomyocytes were treated with leonurine 8 h prior to exposure to hypoxia. In addition, we investigated the effects of 7.5 and 15 mg/kg leonurine, administered to rats i.p. for 7 days prior to left coronary artery ligation, on subsequent infarct size of the ischaemic heart.
• 3 Leonurine significantly increased the viability of cardiomyocytes injured by hypoxia. In the leonurine‐treated group, gene expression levels of pro‐apoptotic genes, namely Bax and Fas, were significantly downregulated (by 0.95‐ and 0.72‐fold, respectively; P < 0.001) compared with the hypoxic control group, whereas the expression of Bcl‐2 and Bcl‐xl was upregulated following leonurine treatment (by 1.03‐ and 1.07‐fold, respectively; P < 0.05). Correspondingly, leonurine treatment increased Bcl‐2 protein levels and decreased Bax protein levels. Assays investigating cardiac anti‐oxidant enzymes provided further evidence for a protective effect of leonurine, as indicated by the induction of the anti‐oxidant enzymes superoxide dismutase and catalase. Furthermore, leonurine decreased infarct size in ischaemic rat heart.
• 4 The results of the present study suggest that the mechanisms of action of leonurine in hypoxic neonatal rat cardiomyocytes and infarcted rat heart may be related to its anti‐oxidant and anti‐apoptotic properties.

     

修饰SOD—CTS复合酶的制备及其性质研究

报道了SOD-CTS复合酶的化学修饰。药用淀粉用高碘酸钠氧化后,与复合酶共价结合制得了修饰酶。与天然酶相比,修饰酶对温度、酸、碱有较强的抗性,且具有较强的抗蛋白酶水解能力,     

THE INFLUENCE OF HISTAMINE ON EPITHELIAL CELL PROLIFERATION IN THE JEJUNUM OF THE RAT

1. The influence of histamine and histamine receptor blockade on the mitotic rate in epithelial cell proliferation in epithelial cells lining the crypts of Lieberkühn in rat jejunum was studied. 2. Histamine injection resulted in an increase in the mitotic rate. This increase in mitotic rate was blocked by metiamide but not by mepyramine. 3. Prevention of histamine synthesis by α-methylhistidine administration did not alter the mitotic rate. 4. The mechanism by which histamine may influence crypt cell proliferation and and possible role of cyclic GMP in this mediation are discussed.     

EFFECT OF CULTURE CONDITIONS PRIOR TO EXPOSURE ON CADMIUM CYTOTOXICITY IN PRIMARY RAT HEPATOCYTES

Primary rat hepatocytes area useful research tool for direct investigation of hepatotoxic effects of chemicals or drugs at the cellular level. USEPA's reevaluation of current human health risk assessment models for thetoxicmetal cadmium has identified a need for the development of new models that include in vitro toxicity and kinetic data. The EC50 for cadmium obtained in rat hepatocyte cultures in 96-well plates (EC50 [96]=3.2 0.8muM) was found to be significantly different from that obtained in 6-well cultures (EC50 [6]=14.8+/-0.7muM). When medium depth in 96-well plates was adjusted to reflect the same depth as that in 6-well plates prior to, during, and following cadmium exposure, an EC50 was observed that was similar to that obtained in 6-well plates (EC50 [96*]=13.2+/-0.9muM). Hepatocytes incubated in 96-well plates with various depths of culture medium, from 1 mm (34muL/well)to 6 mm (200muL/well), exhibited a significant decrease in viability and attached cell protein with greater medium depths. Assessment of various biochemical markers of hepatic function indicated that hepatocytes cultured at 2-mm medium depths were similar to those in vivo. Metal analysis indicated that the amount of cadmium entering hepatocytes was independent of treatment. Thus, differences in toxicity were not a result of differences in cadmium uptake.This study indicated that in vitrotest systems should beoptimized and validated prior to use in mechanistic and kinetic studies, if they are to be considered by regulatory agencies.