氟伐他汀对野百合碱所致的大鼠肺血管重塑和右心室肥厚的影响

目的观察氟伐他汀对野百合碱(MCT)所致的大鼠肺血管重塑和右心室肥厚的影响。方法66只大鼠被随机分为3组:(1)M+F组(n=24):本组大鼠首先给予每日1次MCT(60mg/kg)皮下注射,连续2周,第3周至第6周末给予氟伐他汀(1mg/kg)灌胃,每日1次。(2)MCT组(n=24):实验前2周给予每日1次MCT(60mg/kg)皮下注射,第3周至第6周末给予与氟伐他汀等体积的0.9盐水灌胃;(3)Saline组(n=18):分别于实验前2周及第2周末至第6周末给予等体积的0.9盐水皮下注射和灌胃。MCT注射前记为第0周,实验共观察6周。分别于不同时间点观察大鼠肺组织形态学变化,并对平均肺动脉压(mPAP)、管壁厚度百分比(PWT)、右心室肥厚指数(RVHI)进行测定。结果MCT注射2周后,大鼠出现显著的肺血管重塑和右心室肥厚,MCT组大鼠在MCT停止注射后mPAP、PWT及RVHI进一步增高。而M+F组大鼠在给予连续4周氟伐他汀1mg/(kg.d)灌胃处理后,mPAP(23.3±3.2)mmHg及PWT(42.3±2.7)均较MCT组减轻。RVHI(0.32±0.02)亦较MCT组(0.54±0.03)显著降低,且与正常对照组(Saline组)比较无显著差异。结论氟伐他汀能有效减轻MCT诱导的大鼠肺血管重塑和右心室肥厚。     

2,6-二甲基-4-(2-氯苯基)-1,4-二氢-3,5-吡啶二羧酸二甲酯对大鼠野百合碱性肺动脉高压的防治作用

用野百合碱(MCT)复制大鼠慢性肺动脉高压(PH)病理模型,探讨钙拮抗剂2,6-二甲基-4-(2-氯苯基)-1,4-二氢-3,5-吡啶二羧酸二甲酯(DCDDP)对PH的防治作用. DCDDP 5, 50, 500 μg·kg^-1 ip, 每日1次， 连续28 d; MCT 60 mg· kg^-1在第1次给DCDDP后30 min sc.观察肺血流动力学指标变化,血浆和肺匀浆中内皮素样免疫反应物(ir-ET), 一氧化氮(NO)含量,超氧化物歧化酶(SOD)活性和丙二醛(MDA)含量的改变. 三种不同剂量的DCDDP分别使平均肺动脉压从4.5±0.9 kPa(MCT组)降至3.2±0.2, 3.5±0.6和3.8±0.9 kPa, 肺血管阻力从118±17 kPa·min^-1·L^-1(MCT组)降至65±16, 68±18和76±18 kPa·min^-1·L^-1(P<0.01), 提示在本实验剂量范围内, 中, 低剂量DCDDP防治效果似较好. DCDDP不影响MCT性PH时血浆和肺匀浆中ir-ET的改变, 但可显著升高肺匀浆中NO的含量和SOD活性, 使肺匀浆中MDA含量降至正常, 这可能是其降低肺动脉压的机理之一.     

Roles of endothelin ETA and ETB receptors in the pathogenesis of monocrotaline-induced pulmonary hypertension

The functional roles of endothelin ETA and ETB receptors in the development of monocrotaline (MCT)-induced pulmonary hypertension were investigated using MCT-treated rats in the absence or presence of a daily administration of A-192621, a selective ETB receptor antagonist, ABT-627, a selective ETA receptor antagonist, or a combination of both drugs. Four weeks after the injection of saline or MCT (60 mg/kg, s.c.), cardiac hypertrophy, right ventricular systolic pressure and morphologic changes of pulmonary arteries were evaluated. Compared with the control animals, MCT produced marked pulmonary hypertension associated with increases in right ventricular pressure and hypertrophy, and pulmonary arterial medial thickening. These MCT-induced alterations were markedly suppressed by daily treatment with ABT-627 for 4 weeks (10 mg/kg/d, twice daily), whereas treatment with A-192621 significantly aggravated the above MCT-induced pathologic changes. The blockade of both receptor subtypes by a combination of A-192621 and ABT-627 also significantly improved the MCT-induced pathologic changes, to the same extent as with ABT-627 administration. Thus, an exaggerated response to MCT during ETB receptor blockade also seems to be mediated by ETA receptor activation, thereby suggesting that ETA receptor-mediated action is exclusively contributive to the pathogenesis of MCT-induced pulmonary hypertension, although we cannot rule out a protective role of ETB receptor-mediated action.     

The HMG-CoA reductase inhibitor, pravastatin, prevents the development of monocrotaline-induced pulmonary hypertension in the rat through reduction of endothelial cell apoptosis and overexpression of eNOS

HMG-CoA reductase inhibitors improve endothelial function and exert antiproliferative effects on vascular smooth muscle cells of systemic vessels. This study was aimed to assess the protective effects of pravastatin (an HMG-CoA reductase inhibitor) against monocrotaline-induced pulmonary hypertension in rats. Pravastatin (PS, 10 mg/kg/day) or vehicle were given orally for 28 days to Wistar male rats injected or not with monocrotaline (MC, 60 mg/kg intraperitonealy) and treated or not by N^ω-nitro-L-arginine methyl ester (L-NAME) 15 mg/kg/day. At 4 weeks, monocrotaline-injected rats developed severe pulmonary hypertension, with an increase in right ventricular pressure (RVP) and right ventricle/left ventricle+septum weight ratio (RV/LV+S), associated with a decrease in pulmonary artery dilation induced either by acetylcholine or sodium nitroprusside. Hypertensive pulmonary arteries exhibited an increase in medial thickness, medial wall area, endothelial cell apoptosis, and a decrease of endothelial nitric oxide synthase (eNOS) expression. Monocrotaline-rat lungs showed a significant decrease of eNOS expression (4080±27 vs 12189±761 arbitrary density units [ADU] for MC and control groups respectively, P<0.01) and a significant increase of cleaved caspase-3 expression by western blotting (Control=11628±2395 vs MC=2326±2243 ADU, P<0.05). A non-significant trend toward a reduced mortality was observed with pravastatin (relative risk of death = 0.33; 95% confidence interval [0.08–1.30], P= 0.12 for MC+PS vs MC groups). Pravastatine induced a protection against the development of the pulmonary hypertension (RVP in mmHg: 30±3 vs 45±4 and RV/LV+S: 0.46±0.04 vs 0.62±0.05 for MC+PS and MC groups respectively, P<0.05) and was associated with a significant reduction of MC-induced thickening (61±6 μm vs 81±3 μm for MC+PS and MC groups respectively, P= 0.01) of the medial wall of the small intrapulmonary arteries. Pravastatin partially restored acetylcholine-induced pulmonary artery vasodilation in MC rats (Emax=65±5% and 46±3% for MC+PS and MC group respectively, P<0.05) but had no effect on acetylcholine-induced pulmonary artery vasodilation in MC+L-NAME rats. It also prevented apoptosis and restored eNOS expression of pulmonary artery endothelial cells, as well as in the whole lung. Pravastatin reduces the development of monocrotaline-induced pulmonary hypertension and improves endothelium-dependent pulmonary artery relaxation, probably through a reduced apoptosis and a restored eNOS expression of endothelial cells.     

THE EFFECT OF EXPERIMENTAL RENAL FAILURE ON TOLFENAMIC ACID DISPOSITION IN THE DOG

The pharmacokinetic disposition of tolfenamic acid, an NSAID, after a single administration of tolfenamic acid (4 mg kg⁻¹) by the intravenous (IV) route was compared in eight dogs before and after a surgically induced renal failure. Renal impairment was confirmed by a significant increase ( p <0·001) of water intake, urine volume, and urea and creatinine plasma concentration. PAH and inulin clearances decreased after surgery from 15·2±4·2 to 9·5±0·8 mL kg⁻¹ min⁻¹ ( p <0·05) and from 4·37±1·15 to 2·43±0·88 mL kg⁻¹ min⁻¹ ( p =0·067), respectively. After surgery, clearance of TA was significantly ( p <0·001) increased, from 2·22±1·68 to 3·59±1·81 mL kg⁻¹ min⁻¹. There was no modification of the steady-state volume of distribution ( p >0·05) and the mean residence time was significantly decreased from 606±199 to 373±302 min ( p <0·05). No variation of binding to plasma proteins (<99%) was observed. These results suggest that renal insufficiency could increase hepatic metabolism and/or alter the enterohepatic cycle of TA. © 1997 by John Wiley & Sons, Ltd.     

野百合碱诱导大鼠肺动脉高压动物模型的制备

目的采用注射野百合碱(MCT)制备大鼠肺动脉高压模型,并对肺动脉压测定方法进行优化。方法通过ip MCT诱导建立大鼠肺动脉高压模型,通过测定大鼠肺血管阻力的方法来对大鼠右心室压进行测定,采用阳性药对照、血流动力学测定和组织学观察确定模型是否建立成功。结果 ip 50 mg/kg MCT 4周后大鼠右心室平均压、右心肥大指数对比对照组明显增高,观察病理组织切片,可见明显的内皮细胞损伤,分布不均,动脉管壁明显增厚,肺组织有大量的炎性细胞浸润,出现肺血管的重构,证实肺动脉高压动物模型造模成功。结论采用ip MCT可以建立稳定的大鼠肺动脉高压模型,且具有较高的存活率,同时建议采用改良的心导管测定方法测定大鼠右心室压力。     

PHARMACOKINETICS OF THE ENANTIOMERS OF VERAPAMIL AFTER INTRAVENOUS AND ORAL ADMINISTRATION OF RACEMIC VERAPAMIL IN A RAT MODEL

Verapamil is a chiral calcium channel blocking drug which is useful clinically as the racemate in treating hypertension and arrhythmia. The published pharmacokinetic data for verapamil enantiomers in the rat model are limited. Utilizing a stereospecific high-performance liquid chromatographic (HPLC) assay, the enantiomeric disposition of verapamil is reported after intravenous (1·0 mg kg⁻¹) and oral (10 mg kg⁻¹) administration of racemic verapamil to the rat model. After intravenous administration the systemic clearance of R-verapamil was significantly greater than that of S-verapamil; 34·9 ± 7 against 2·7 ± 3·7 mL min⁻¹ kg⁻¹ (mean ± SD), respectively. After oral administration, the clearance of R-verapamil was significantly greater than that of S-verapamil, 889 ± 294 against 351 ± 109 mL min⁻¹ kg⁻¹, respectively. The apparent oral bioavailability of S-verapamil was greater than that of R-verapamil, 0·074 ± 0·031 against 0·041 ± 0·011, respectively. These data suggest that the disposition of verapamil in the rat is stereoselective; verapamil undergoes extensive stereoselective first-pass clearance after oral administration and the direction of stereoselectivity in plasma is opposite to that observed in the human. © 1997 John Wiley & Sons, Ltd.     

Withania somnifera shows a protective effect in monocrotaline-induced pulmonary hypertension

Abstract

Context: Withania somnifera (Linn.) Dunal (Solanaceae), a clinically used herbal drug in Ayurveda, shows potent antioxidant, anti-inflammatory, pro-apoptotic, and cardioprotective effects. However, the efficacy of W. somnifera in pulmonary hypertension (PH), a cardiopulmonary disorder, remains unexplored.

Objective: The present study investigates the effect of W. somnifera root powder on monocrotaline (MCT)-induced PH in rats.

Materials and methods: In preventive studies, W. somnifera root powder (50 and 100?mg/kg/d, p.o.) was administered from day 1 following single administration of MCT (60?mg/kg, s.c.) in Sprague–Dawley (SD) rats. After 35?d, right ventricular pressure (RVP) was measured in anesthetized rats. Various physical markers of right ventricular hypertrophy (RVH) were measured in isolated hearts. Markers of endothelial function, inflammation, and oxidative stress were estimated in lung homogenate. Vasoreactivity of pulmonary arteries was also studied. In therapeutic treatment, W. somnifera (50 and 100?mg/kg/d, p.o.) was administered from day 21 to 35 post-MCT administration.

Results: Preventive treatment with 50 and 100?mg/kg W. somnifera significantly reduced the RVP (32.18?±?1.273?mm?Hg and 29.98?±?1.119?mm?Hg, respectively, versus 42.96?±?1.789?mm?Hg of MCT) and all markers of RVH in MCT-challenged rats. There was an improvement in inflammation, oxidative stress and endothelial dysfunction, and attenuation of proliferative marker and apoptotic resistance in lungs. Therapeutic treatment with W. somnifera (100?mg/kg) also reduced RVP and RVH.

Discussion: This study demonstrated that W. somnifera significantly protected against MCT-induced PH due to its antioxidant, anti-inflammatory, pro-apoptotic, and cardioprotective properties.     

钙拮抗剂在心肌肥厚时对β受体阻滞剂撤药的影响

用腹主动脉结扎4周引起的压力超负荷型左室肥厚大鼠,观察长期大剂量用美托洛尔(metoprolol,Met)突然撤药1d后的血流动力学变化、心肌β受体变化,及硝苯地平(nifedipine,Nif),间硝地平(m-nifedipine,m-Nif)对这些变化的影响。Nif和m-Nif在减轻心肌肥厚的同时,均可缓解Met撤药后平均动脉压和左室收缩压的异常增高,并可防止β受体的上调。本结果提示合用钙拮抗剂可预防β阻滞剂的撤药反应。     

Estradiol metabolites attenuate monocrotaline-induced pulmonary hypertension in rats

Pulmonary arterial hypertension (PH) is a deadly disease characterized by pulmonary arterial vasoconstriction and hypertension, pulmonary vasculature remodeling, and right ventricular hypertrophy. Our previous in vivo studies, performed in several models of cardiac, vascular, and/or renal injury, suggest that the metabolites of 17beta-estradiol may inhibit vascular and cardiac remodeling. The goal of this study was to determine whether 2-methoxyestradiol (2ME), major non-estrogenic estradiol metabolite, prevents the development and/or retards the progression of monocrotaline (MCT)-induced PH. First, a total of 27 male Sprague Dawley rats were injected with distillated water (Cont, n=6) or monocrotaline (MCT; 60 mg/kg, i.p.; n=21). Subsets of MCT animals (n=7 per group) received 2ME or its metabolic precursor 2-hydroxyestradiol (2HE; 10 microg/kg/h via osmotic minipumps) for 21 days. Next, an additional set (n=24) of control and MCT rats was monitored for 28 days, before right ventricular peak systolic pressure (RVPSP) was measured. Some pulmonary hypertensive animals (n=8) were treated with 2ME (10 microg/kg/h) beginning from day 14 after MCT administration. MCT caused pulmonary hypertension (ie, increased right ventricle/left ventricle+septum [RV/LV+S] ratio and wall thickness of small-sized pulmonary arteries, and elevated RVPSP) and produced high and late (days 22 to 27) mortality. Pulmonary hypertension was associated with strong proliferative response (PCNA staining) and marked inflammation (ED1+cells) in lungs. Both metabolites significantly attenuated the RV/LV+S ratio and pulmonary arteries media hypertrophy and reduced proliferative and inflammatory responses in the lungs. Furthermore, in diseased animals, 2ME (given from day 14 to 28) significantly decreased RVPSP, RV/LV+S ratio and wall thickness, and reduced mortality by 80% (mortality rate: 62.5% vs. 12.5%, MCT vs. MCT+2ME day 14 to 28). This study provides the first evidence that 2ME, a major non-estrogenic, non-carcinogenic metabolite of estradiol, prevents the development and retards the progression of monocrotaline-induced pulmonary hypertension. Further evaluation of 2ME for management of pulmonary arterial hypertension is warranted.     

Pharmacokinetics and tissue disposition of danofloxacin in sheep

The plasma pharmacokinetics of danofloxacin administered at 1.25 mg kg⁻¹ body weight by the intravenous and intramuscular routes were determined in sheep. Tissue distribution was also determined following administration by the intramuscular route at 1.25 mg kg⁻¹ body weight. Danofloxacin had a large volume of distribution at steady state (V_ss) of 2.76±0.16 h (mean±S.E.M.) L kg⁻¹, an elimination half-life (t_1/2β) of 3.35±0.23 h, and a body clearance (C1) of 0.63±0.04 L kg⁻¹ h⁻¹. Following intramuscular administration it achieved a maximum concentration (C_max) of 0.32±0.02 μg mL⁻¹ at 1.23±0.34 h (t_max) and had a mean residence time (MRT) of 5.45±0.19 h. Danofloxacin had an absolute bioavailability (F) of 95.71±4.41% and a mean absorption time (MAT) of 0.81±0.20 h following intramuscular administration. Mean plasma concentrations of >0.06 μg mL⁻¹ were maintained for more than 8 h following intravenous and intramuscular administration. Following intramuscular administration highest concentrations were measured in plasma (0.43±0.04 μg mL⁻¹), lung (1.51±0.18 μg g⁻¹), and interdigital skin (0.64±0.18 μg g⁻¹) at 1 h, duodenal contents (0.81±0.40 μg mL⁻¹), lymph nodes (4.61±0.35 μg g⁻¹), and brain (0.06±0.00 μg mL⁻¹) at 2 h, jejunal (10.50±4.31 μg mL⁻¹) and ileal (5.25±1.67 μg mL⁻¹) contents at 4 h, and colonic contents (8.94±0.65 μg mL⁻¹) at 8 h. © 1998 John Wiley & Sons, Ltd.     

A novel and selective endothelin ET(A) receptor antagonist YM598 prevents the development of chronic hypoxia-induced pulmonary hypertension in rats

The preventive effects of the novel and selective endothelin ET(A) receptor antagonist YM598 on the development of pulmonary hypertension (PH) were investigated in chronic hypoxia-induced PH rats. Oral administration of YM598 at a dose of 1 mg/kg was started on the first day of chronic hypoxia exposure for 2 and 3 weeks to investigate the effects of this compound on hemodynamic and arterial blood gas variables, respectively. Cardiopulmonary organ weights were measured at the end of the 2-week administration period. Chronic hypoxia for 2 weeks induced a marked increase in pulmonary arterial pressure, right ventricular hypertrophy, and pulmonary and systemic congestion, and a decrease in right cardiac diastolic function. Repeated oral administration of YM598 significantly suppressed the increase in pulmonary arterial pressure, right ventricular hypertrophy, and pulmonary and systemic congestion. YM598 also improved the hypoxemia which was induced by 3 weeks of exposure to hypoxia. These results suggest that repeated oral administration of YM598 to rats with chronic hypoxia effectively prevented the development of PH. Oral administration of YM598 also improved hypoxemia in this model. These data strongly suggest that YM598 will be clinically useful in the treatment of patients with either primary or secondary pulmonary hypertension.     

THE PHARMACOKINETICS OF 1954U89, 1, 3-DIAMINO-7-(1-ETHYLPROPYL)-8-METHYL-7H-PYRROLO-(3, 2-f )QUINAZOLINE,IN DOGS AND RATS AFTER INTRAVENOUS AND ORAL ADMINISTRATION

1954U89, 1, 3-diamino-7-(1-ethylpropyl)-8-methyl-7H-pyrrolo-(3, 2-f )quinazoline, is a potent, lipid-soluble inhibitor of dihydrofolate reductase. The pharmacokinetics and bioavailability of 1954U89 were examined in male beagle dogs and male CD rats. Dogs received single intravenous (2·5 mg kg⁻¹) and oral (5·0 mg kg⁻¹) doses of 1954U89 with and without successive administration of calcium leucovorin. Single intravenous (5·0 mg kg⁻¹) and oral (10 mg kg⁻¹) doses of [1,3-¹⁴C₂]1954U89 were administered to rats. Plasma concentrations of total radiocarbon were determined by scintillation counting, and intact 1954U89 was measured by HPLC. The mean plasma half-life was 3·2 ± 0·62 and 4·2 ± 0·68 h after intravenous and oral administration, respectively, to dogs. The pooled plasma half-life after intravenous administration to rats averaged 1·2 h; a reliable plasma half-life value after oral administration could not be determined. Mean total-body clearance was 2·4 ± 0·39 and 4·5 ± 1·1 L h⁻¹ kg⁻¹ after intravenous and oral administration, respectively, to dogs, and averaged 12 and 77 L h⁻¹ kg⁻¹ after intravenous and oral administration, respectively, to rats. Neither clearance nor bioavailability of 1954U89 in dogs was affected significantly by administration of calcium leucovorin. Absolute bioavailability was 54 ± 12% in dogs and 16% in rats. © 1997 John Wiley & Sons, Ltd.     

Beneficial effects of a novel agonist of the adenosine A2A receptor on monocrotaline-induced pulmonary hypertension in rats

Background and Purpose

Pulmonary arterial hypertension (PAH) is characterized by enhanced pulmonary vascular resistance, right ventricular hypertrophy and increased right ventricular systolic pressure. Here, we investigated the effects of a N-acylhydrazone derivative, 3,4-dimethoxyphenyl-N-methyl-benzoylhydrazide (LASSBio-1359), on monocrotaline (MCT)-induced pulmonary hypertension in rats.

Experimental Approach

PAH was induced in male Wistar rats by a single i.p. injection of MCT (60 mg·kg⁻¹) and 2 weeks later, oral LASSBio-1359 (50 mg·kg⁻¹) or vehicle was given once daily for 14 days. Echocardiography was used to measure cardiac function and pulmonary artery dimensions, with histological assay of vascular collagen. Studies of binding to human recombinant adenosine receptors (A₁, A_2A, A₃) and of docking with A_2A receptors were also performed.

Key Results

MCT administration induced changes in vascular and ventricular structure and function, characteristic of PAH. These changes were reversed by treatment with LASSBio-1359. MCT also induced endothelial dysfunction in pulmonary artery, as measured by diminished relaxation of pre-contracted arterial rings, and this dysfunction was reversed by LASSBio-1359. In pulmonary artery rings from normal Wistar rats, LASSBio-1359 induced relaxation, which was decreased by the adenosine A_2A receptor antagonist, ZM 241385. In adenosine receptor binding studies, LASSBio-1359 showed most affinity for the A_2A receptor and in the docking analyses, binding modes of LASSBio-1359 and the A_2A receptor agonist, {"type":"entrez-protein","attrs":{"text":"CGS21680","term_id":"878113053","term_text":"CGS21680"}}CGS21680, were very similar.

Conclusion and Implications

In rats with MCT-induced PAH, structural and functional changes in heart and pulmonary artery were reversed by treatment with oral LASSBio-1359, most probably through the activation of adenosine A_2A receptors.     

The protective effect of HMG-CoA reductase inhibitors against monocrotaline-induced pulmonary hypertension in the rat might not be a class effect: comparison of pravastatin and atorvastatin

Hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, so called statins, improve endothelial function and exert antiproliferative effects on vascular smooth muscle cells of systemic vessels. This study aimed at comparing the protective effects of two statins, pravastatin and atorvastatin, against monocrotaline (MC)-induced pulmonary hypertension in rats. Pravastatin or atorvastatin (PS or AS, 10 mg/kg per day) or vehicle were given orally for 28 days to Wistar male rats injected or not with MC (60 mg/kg intraperitoneally). At 4 weeks, MC-injected rats developed severe pulmonary hypertension, with an increase in right ventricular pressure (RVP) and right ventricle/left ventricle + septum weight ratio associated with a decrease in acetylcholine- or sodium-nitroprusside-induced pulmonary artery dilation observed in vitro. Hypertensive pulmonary arteries exhibited an increase in medial thickness and endothelial cell apoptosis and a decrease of endothelial nitric oxide synthase (eNOS) expression. MC-rat lungs showed a significant decrease of eNOS (P < 0.01) and increase of cleaved caspase-3 (P < 0.05) expression determined by Western blotting. PS (P = 0.02) but not AS (P = 0.30) significantly limited the development of pulmonary hypertension (RVP in mmHg: 30 ± 3, 36 ± 4 vs. 45 ± 4 and 14 ± 1 for MC + PS, MC + AS, MC, and control groups, respectively). Both statins significantly reduced MC-induced right ventricle hypertrophy [RV/left ventricular (LV) + S, in mg/g: 0.46 ± 0.04, 0.39 ± 0.03, 0.62 ± 0.05 and 0.29 ± 0.01 for MC + PS, MC + AS, MC, and control groups, respectively; P < 0.05),and reduced MC-induced thickening (61 ± 6 μm, 82 ± 5 μm, 154 ± 4 μm, and 59 ± 2 μm for MC + PS, MC + AS, MC, and control groups, respectively; P = 0.01) of small intrapulmonary artery medial wall, with MC + AS still being different from the control group. PS but not AS partially restored acetylcholine-induced pulmonary artery vasodilation in MC rats (E_max=65 ± 5%, 49 ± 6%, 46 ± 3%, and 76 ± 4% for MC + PS, MC + AS, MC, and control groups, respectively; P < 0.05 for MC + PS vs. other groups). Both statins prevented apoptosis and restored eNOS expression of pulmonary artery endothelial cells as well as in the whole lung with a more pronounced effect with PS compared with AS. In conclusion, despite its effects on eNOS expression, apoptosis, and medial wall thickening, AS was unable to significantly reduce pulmonary hypertension and to restore endothelium-dependent relaxation, suggesting intermolecular differences between the two HMG-CoA reductase inhibitors in the protection against MC-induced hypertension.     

Polyamine synthesis blockade in monocrotaline-induced pneumotoxicity

Based on the documented regulatory role of polyamines in cell growth and differentiation, we have proposed that these organic cations are involved with the development of monocrotaline (MCT)-induced hypertensive pulmonary vascular disease. Two lines of evidence support this hypothesis: (1) MCT causes progressive increases in lung polyamine contents which are temporarily related to the development of cardiopulmonary abnormalities, and (2) blockade of polyamine synthesis with the site-selective enzyme-activated inhibitor, alpha-difluoromethylornithine (DFMO), attenuates development of medial arterial thickening, increased pulmonary arterial pressure, and right ventricular hypertrophy. To evaluate the mechanism of DFMO protection, the present study assessed when, during the course of MCT-induced pneumotoxicity, DFMO exerts its salutary effects, and determined if the protection afforded by DFMO could be reversed through supplementation with exogenous polyamines. To address the first issue, rats were treated with 30 mg/kg MCT and, 10 days after administration when lung polyamine contents were augmented and when pulmonary edema was evident, DFMO treatment was initiated as a 2% solution in the drinking water. In animals receiving MCT only, lung polyamine contents were elevated and right ventricular hypertrophy was evident at both 20 and 35 days after treatment. DFMO treatment initiated at day 10 attenuated the increases in putrescine and spermidine but not spermine and reduced the degree of right ventricular hypertrophy at both the 20- and 35-day time points. To determine if the blockade by DFMO could be reversed by supplementation with exogenous polyamines, animals were treated simultaneously with MCT and DFMO as described above and the immediate precursor to the polyamines, ornithine, was added to the drinking water as a 2% solution. Relative to animals receiving MCT and DFMO, ornithine supplementation increased lung polyamine contents to levels normally associated with MCT treatment only. Ornithine also reversed the protection against right ventricular hypertrophy normally afforded by DFMO. These observations indicate that the salutary effects of DFMO in MCT-induced pulmonary hypertension cannot be ascribed solely to interference in the early events after MCT treatment and that restoration of lung polyamine contents to high levels by supplementation with exogenous ornithine reverses DFMO protection against sustained pulmonary hypertension. It is concluded, therefore, that polyamines play a central role in delayed responses of lung cells underlying the development of MCT-induced sustained pulmonary hypertension.     

Simvastatin-tacrolimus and simvastatin-cyclosporin interactions in rats

The effect of simvastatin (SV)-tacrolimus (TL) and simvastatin-cyclosporin (CyA) interactions on creatine phosphokinase levels and renal and hepatic function were investigated in rats. Animals were divided into seven groups; (1) SV (150 mg kg⁻¹ oral) alone, (2) SV+TL (150 mg kg⁻¹ oral+0.5 mg kg⁻¹ intraperitoneal (i.p.)), (3) TL (0.5 mg kg⁻¹ i.p.) alone, (4) SV+CyA (150 mg kg⁻¹ oral+10 mg kg⁻¹ oral), (5) CyA (10 mg kg⁻¹ oral) alone, (6) control vehicle for oral administration, and (7) control vehicle for i.p. administration. A marked reduction in body weight and mortality was observed in the (SV+CyA) and (SV+TL) groups. Plasma creatine kinase levels in the (SV), (TL), (SV+CyA) and (SV+TL) groups, 7 days postadministration, were significantly higher compared with those before administration (p <0.05). The plasma urea nitrogen levels in the (TL), (SV+CyA) and (SV+TL) groups after 7 days of administration were significantly higher than those of the controls. In addition, a marked increase in the plasma levels of alanine and aspartate amino transferases were observed in the (SV+CyA) groups. © 1998 John Wiley & Sons, Ltd.     

PHARMACOKINETICS AND HAEMATOLOGICAL PARAMETERS OF RECOMBINANT HUMAN ERYTHROPOIETIN AFTER SUBCUTANEOUS ADMINISTRATIONS IN HORSES

The pharmacokinetics of recombinant human Epo (rHuEpo) were investigated after subcutaneous administration to horses. Four horses received a single 30 IU kg⁻¹ dose of rHuEpo. One horse received three repeated doses of 120 IU kg⁻¹ at 48 h intervals. Plasma erythropoietin (Epo) was measured by radioimmunoassay. In both cases pharmacokinetic parameters were evaluated using a one-compartment open model and first-order input and output rates. The mean values (±SD) for elimination half-life, CL/F, and V_d/F after a single dose were 12·9±3·34 h, 11·8±4·96 L h⁻¹, and 233±126 L, respectively. After repeated doses, elimination half-life, CL/F, and V_dss/F were 11·3 h, 8·94 L h⁻¹, and 145·6 L, respectively. No significant differences were observed between the haematological parameters after a single 30 IU kg⁻¹ administration compared to baseline values. Multiple and high doses of rHuEpo modified red blood cells, haemoglobin, and hematocrit. According to our results, plasma Epo assay can help, during an antidoping control procedure, to support a positive result only up to 72 h after the last rHuEpo     

Selective activation of angiotensin AT2 receptors attenuates progression of pulmonary hypertension and inhibits cardiopulmonary fibrosis

Background and Purpose

Pulmonary hypertension (PH) is a devastating disease characterized by increased pulmonary arterial pressure, which progressively leads to right-heart failure and death. A dys-regulated renin angiotensin system (RAS) has been implicated in the development and progression of PH. However, the role of the angiotensin AT₂ receptor in PH has not been fully elucidated. We have taken advantage of a recently identified non-peptide AT₂ receptor agonist, Compound 21 (C21), to investigate its effects on the well-established monocrotaline (MCT) rat model of PH.

Experimental Approach

A single s.c. injection of MCT (50 mg·kg⁻¹) was used to induce PH in 8-week-old male Sprague Dawley rats. After 2 weeks of MCT administration, a subset of animals began receiving either 0.03 mg·kg⁻¹ C21, 3 mg·kg⁻¹ PD-123319 or 0.5 mg·kg⁻¹ A779 for an additional 2 weeks, after which right ventricular haemodynamic parameters were measured and tissues were collected for gene expression and histological analyses.

Key Results

Initiation of C21 treatment significantly attenuated much of the pathophysiology associated with MCT-induced PH. Most notably, C21 reversed pulmonary fibrosis and prevented right ventricular fibrosis. These beneficial effects were associated with improvement in right heart function, decreased pulmonary vessel wall thickness, reduced pro-inflammatory cytokines and favourable modulation of the lung RAS. Conversely, co-administration of the AT₂ receptor antagonist, PD-123319, or the Mas antagonist, A779, abolished the protective actions of C21.

Conclusions and Implications

Taken together, our results suggest that the AT₂ receptor agonist, C21, may hold promise for patients with PH.     

Evaluation of olmesartan medoxomil in the rat monocrotaline model of pulmonary hypertension

It is suggested that angiotensin II is involved in the pathogenesis of pulmonary hypertension and subsequent right ventricular hypertrophy; therefore, an angiotensin AT1 receptor antagonist could be beneficial for the treatment of this disease. We tested the effect of the new AT1 receptor antagonist olmesartan medoxomil on monocrotaline-induced pulmonary hypertension in rats. At 3 weeks after a single subcutaneous injection of monocrotaline (50 mg/kg), the lung/body weight ratio, the right ventricle/(left ventricle plus septum) weight ratio [RV/(LV+S)], and right ventricular systolic pressure were increased, indicating establishment of pulmonary hypertension and right ventricular hypertrophy. Oral administration of olmesartan medoxomil (2 or 5 mg/kg/day for 3 weeks) restored RV/(LV+S) and right ventricular systolic pressure, and a higher dose (5 mg/kg/day) improved the lung/body weight ratio. Pulmonary arteries isolated from monocrotaline-treated rats exhibited an increase in basal tone in the resting state, indicating that they had intrinsic tone. Three weeks of treatment with olmesartan decreased this intrinsic tone. These data suggest that long-term treatment with olmesartan has beneficial effects on monocrotaline-induced pulmonary hypertension and subsequent right ventricular hypertrophy.