Diuretic and hypotensive actions of torasemide in hypertensive models of rat

The diuretic and the antihypertensive actions of torasemide were examined in renal and genetic hypertensive rats and compared to the effects of furosemide. Oral administration of torasemide (1 and 3 mg/kg) elicited a dose-dependent increase in the excretion of urine and electrolytes and elevated the urinary Na/K ratio in both renal and genetic hypertensive rats. Torasemide and furosemide had a similar maximum diuretic effect in the normotensive Wistar rat and the spontaneously hypertensive rat (SHR). However, the diuretic activity of furosemide was weaker in the renal hypertensive rat (RHR). Torasemide showed approximately 30 times greater diuretic potency than furosemide. Torasemide and furosemide demonstrated hypotensive action in hypertensive rat models, but not in the normotensive Wistar rat. Especially in the RHR, torasemide exhibited a more potent hypotensive action than furosemide. These results show that the diuretic and antihypertensive activities of torasemide are effective in various rat models of hypertension, while the diuretic activity of furosemide is weak in certain hypertensive rat models. © 1992 Wiley-Liss, Inc.     

Torasemide (LUPRAC): a review of its pharmacological and clinical profile

Loop diuretics potently excrete water and electrolytes and therefore have been widely prescribed for the treatment of various kinds of edema for a long time. The potent diuretic action of loop diuretics, however, often causes hypokalemia, and therefore potassium sparing diuretics have also been supplied as a concomitant drug. Torasemide (LUPRAC), a novel diuretics, shows not only an effective loop diuretic action but also a potassium sparing action due to its anti-aldosteronergic effect. Torasemide also has a high bioavailability and is only slightly influenced by meals in humans. In addition, its pharmacodynamic features contribute to its stable diuretic action without any individual differences. In animal experiments, torasemide showed about a tenfold more potent diuretic action in comparison with furosemide, an authentic loop diuretic. On the one hand, the increase in the urinary potassium excretion by torasemide was relatively slight compared to the increase in urinary sodium excretion and, as a result, the urinary sodium to potassium (Na+/K+) ratio increased. The diuretic profile of torasemide was equal to that of the concomitant use of furosemide and an anti-aldosteronergic drug, spironolactone. Torasemide showed a significant efficacy and safety in comparison with furosemide in the patients with edema in both domestic and foreign clinical studies. Moreover, torasemide also showed a decreased rate of cardiac death in comparison to furosemide in patients with chronic heart failure in a large-scale clinical study (TORIC Study). The difference in cardiac death between these two diuretics has been suggested to depend on the anti-aldosteronergic effect of torasemide. In Japan, no new loop diuretics have been developed in over 10 years. Torasemide is therefore expected to be useful as an effective diuretic for diseases with edema.     

Pharmacological properties of the new potent diuretic torasemide in rats and dogs

Torasemide, a pyridine-3-sulfonylurea derivative, has potent diuretic activity in rats and dogs. In both species urinary volume and electrolyte excretion increased linearly with the logarithm of the dose, thus resembling the profile of a high ceiling diuretic. The minimum effective dose by oral route was 0.2 mg/kg in the rat and less that 0.1 mg/kg in the dog. Maximal effect was obtained with about 10 mg/kg. Experiments by oral and i.v. routes in the rat indicated that torasemide was equally potent by both oral and parenteral administration. In both rats and dogs, urinary excretions induced by torasemide were similar to those obtained with furosemide. However, for the same natriuretic effect, potassium losses with torasemide were significantly less than with furosemide. On a weight basis, torasemide was 9-40 times more potent than furosemide in the rat and about 10 times in the dog. After oral administration the diuretic effects of torasemide started within 20 min and lasted approximately 2 h in the rat and more than 8 h in the dog. The activity of torasemide was not decreased after a repeated daily oral dose of 10 mg/kg for 15 days in the rat. Torasemide at a daily oral dose of 5 mg/kg for 12 days effectively reduced the arterial blood pressure in desoxycortone induced hypertension in the rat. Besides the diuretic and antihypertensive effects no other significant pharmacological effects were observed with torasemide in the different in vitro and in vivo experiments. Torasemide was practically fully absorbed by the gastrointestinal tract, its bioavailability by oral route ranged from 80 to 100%.(ABSTRACT TRUNCATED AT 250 WORDS)     

EFFECTS OF TORASEMIDE ON RENAL HAEMODYNAMICS AND FUNCTION IN ANAESTHETIZED DOGS

1. We examined the effects of torasemide (0.3 and 1 mg/kg i.v.) on renal haemodynamics and function employing renal clearance and stop-flow techniques in anaesthetized dogs and compared these with furosemide (1 and 3 mg/kg i.v.). 2. Torasemide and furosemide did not influence renal haemodynamics, in the renal clearance study, but caused a dose-related and significant increase in urine flow and urinary excretion of sodium and potassium. Torasemide and furosemide increased fractional excretion of sodium in the distal tubules with a relatively small increase in the fractional excretion of lithium (index of sodium excretion at the proximal tubules, FELi). The diuretic profile of torasemide was of long duration, compared with that of furosemide. 3. Torasemide and furosemide inhibited sodium reabsorption at the distal portion of the tubules in the stop-flow study. 4. It is suggested from these results, that the main diuretic site of action of torasemide is the ascending limb of the loop of Henlé.     

Comparative effects of torasemide and furosemide in rats with heart failure

It has been reported that torasemide but not furosemide, may block the renin-angiotensin-aldosterone system and therefore it might attenuate myocardial remodeling accompanied by left ventricular (LV) dysfunction. We therefore compared the therapeutic effects of torasemide, a long-acting loop diuretic, and furosemide, a short-acting one, on the progression of LV remodeling in a rat model of chronic heart failure (CHF) after experimental autoimmune myocarditis (EAM). CHF was elicited in Lewis rats by immunization with porcine cardiac myosin. Twenty-eight days after immunization, rats were treated for 28 days with torasemide, furosemide, or vehicle. We investigated the effects on metabolic and neurohumoral parameters, cardiac fibrosis and remodeling in EAM rats. Diuresis was increased dose dependently by both torasemide and furosemide, showed an equipotent natriuretic effect. The urinary potassium excretion was significantly increased with furosemide in comparison to torasemide. Myocardial functional parameters were significantly improved by torasemide. Conversely, these parameters did not change in rats receiving furosemide. Torasemide suppressed LV fibrosis, myocardial protein levels of transforming growth factor-beta1, collagen III, and aldosterone synthase and improved survival rate to the control level, but furosemide did not. Moreover, both pharmacological interventions significantly elevated plasma angiotensin II and decreased atrial natriuretic peptide in a dose-dependent manner. Our results demonstrate that compared with furosemide, torasemide treatment significantly improved survival rate, LV function and ameliorated the progression of cardiac remodeling in rats with CHF after EAM.     

Torasemide, a long-acting loop diuretic, reduces the progression of myocarditis to dilated cardiomyopathy

Torasemide is a long-acting loop diuretic that combines the effects of both furosemide and spironolactone. It has been reported that torasemide may block the renin-angiotensin-aldosterone system and therefore it might attenuate myocardial remodeling accompanied by left ventricular dysfunction. However, nothing is known about the effect of torasemide on myocardial remodeling in a rat model in which myosin-induced experimental autoimmune myocarditis might develop into dilated cardiomyopathy. Experimental autoimmune myocarditis was elicited in Lewis rats by immunization with porcine cardiac myosin. Twenty-eight days after immunization, we investigated the effects of torasemide on metabolic and neurohumoral parameters, cardiac fibrosis and remodeling in experimental autoimmune myocarditis rats. Diuresis was increased dose-dependently by torasemide; the urinary potassium and sodium excretion was significantly decreased and increased, respectively. Myocardial functional parameters measured by hemodynamic and echocardiographic studies were significantly improved by torasemide treatment in a dose-dependent manner. The area of fibrosis, myocyte size and the myocardial protein levels of transforming growth factor-beta1, collagen III, and aldosterone synthase were significantly decreased, and the sarcoplasmic reticulum Ca2+ ATPase2 protein level was significantly increased by torasemide treatment. Moreover, the plasma levels of angiotensin II and aldosterone were increased and atrial natriuretic peptide was decreased in a dose-dependent manner. Our results indicate that torasemide treatment significantly improved left ventricular function and ameliorated the progression of cardiac remodeling beyond its renal effects in rats with chronic heart failure after experimental autoimmune myocarditis.     

Pharmacokinetics and pharmacodynamics of intravenous trasemide in mutant Nagase analbuminemic rats

The importance of plasma protein binding of intravenous furosemide in circulating blood for its urinary excretion and hence its diuretic effects in mutant Nagase analbuminemic rats (NARs, an animal model for human familial analbuminemia) was reported. Based on the furosemide report, the diuretic effects of another loop diuretic, torasemide, could be expected in NARs if plasma protein binding of torasemide is considerable in the rats. This was proven by this study. After intravenous administration of torasemide, 10 mg/kg, to NARs, the plasma protein binding of torasemide was 23.3% in the rats due to binding to alpha- and beta-globulins (this value, 23.3%, was greater than only 12% for furosemide), and hence the percentages of intravenous dose of torasemide excreted in 8-h urine as unchanged drug was 14.9% in the rat (this value was considerably greater than only 7% for furosemide). After intravenous administration of torasemide to NARs, the AUC (301 versus 2680 microg/min/ml) was significantly smaller [due to significantly faster both Cl(r) (4.81 versus 0.386 ml/min/kg) and Cl(nr) (28.3 versus 3.33 ml/min/kg)], terminal half-life (18.3 versus 73.5 min) and mean residence time (6.97 versus 61.8 min) were significantly shorter (due to faster Cl, 33.2 versus 3.74 ml/min/kg), and amount of 8-h urinary excretion of unchanged torasemide (446 versus 323 microg, due to increase in intrinsic renal excretion) was significantly greater than those in control rats. The 8-h urine output and 8-h urinary excretions of sodium and chloride were comparable between two groups of rats although the 8-h urinary excretion of torasemide was significantly greater in NARs. This could be explained by the following. The amount of urinary excretion of torasemide was significantly greater in NARs than that in control rats only between 0 and 30 min urine collection. In both groups of rats, the urinary excretion rate of torasemide during 0-30 min reached an upper plateau with respect to urine flow rate as well urinary excretion rates of sodium and chloride. Therefore, the diuretic effects (8-h urine output and 8-h urinary excretions of sodium and chloride) were not significantly different between the two groups of rats.     

Torasemide. A review of its pharmacological properties and therapeutic potential.

Torasemide (torsemide) is a high-ceiling loop diuretic which acts on the thick ascending limb of the loop of Henle to promote rapid and marked excretion of water, sodium and chloride. Like furosemide (frusemide), its major site of action is from the luminal side of the cell. Torasemide is at least twice as potent as furosemide on a weight-for-weight basis, produces equivalent diuresis and natriuresis at lower urinary concentrations and has a longer duration of action, allowing once-daily administration without the paradoxical antidiuresis seen with furosemide. Torasemide also appears to promote excretion of potassium and calcium to a lesser extent than furosemide. In trials of up to 48 weeks' duration in patients with mild to moderate essential hypertension, torasemide, administered as a single daily dose, has been shown to achieve adequate blood pressure control reaching steady-state within 8 to 12 weeks. Those patients not responding initially have generally responded to a doubling of the dose. Comparative trials of up to 6 months show torasemide is as effective as indapamide, hydrochlorothiazide or a combination of triamterene/hydrochlorothiazide in maintaining control of blood pressure. Torasemide has also been used successfully to treat oedematous states associated with chronic congestive heart failure, renal disease and hepatic cirrhosis. In short term trials control of blood pressure, bodyweight and residual oedema has been sustained. Torasemide appears to be a useful alternative to furosemide in these patients, providing potent and long-lasting diuresis while being relatively potassium and calcium sparing. In clinical trials to date torasemide has been well tolerated with adverse effects of a mild, transient nature reported by only small numbers of patients. Changes in biochemical parameters have been common, including decreases in plasma sodium and potassium levels and increases in plasma creatinine and uric acid levels. These changes are typical of loop diuretics. No changes were clinically significant nor were clinically relevant changes noted in glucose metabolism, cholesterol or triglyceride levels or in haematological values. Thus, torasemide is an interesting new loop diuretic with potential use in the treatment of mild to moderate essential hypertension and of oedematous states in which diuretic therapy is warranted. Preliminary studies suggest it to be as efficacious as other diuretics in common use and to have some advantage over furosemide in duration of action and in effects on potassium and calcium. However, further long term trials in larger groups of patients are needed to delineate the place of torasemide in therapy fully, both as a single agent and in combination with other currently accepted drug regimens.     

Vasodilatory action of loop diuretics: a plethysmography study of endothelial function in forearm arteries and dorsal hand veins in hypertensive patients and controls

INTRODUCTION: Intravenous administration of loop diuretics induces venodilation before the diuretic response. We investigated whether furosemide and torasemide exert a dilatory effect on arteries and veins mediated by endothelial release of nitric oxide. METHODS: We performed intermittent venous occlusion plethysmography to study forearm blood flow and dorsal hand-vein distension in response to furosemide and torasemide infusion in hypertensive patients and healthy controls. RESULTS: Furosemide increased venodilation from 0.56 +/- 0.09 to 0.88 +/- 0.06 (P=0.000) in control subjects and from 0.49 +/- 0.10 to 0.75 +/- 0.12 (P=0.000) in hypertensive patients. Torasemide increased venodilation from 0.46 +/- 0.06 to 0.70 +/- 0.11 (P=0.007) in control subjects and from 0.48 +/- 0.09 to 0.67 +/- 0.12 (P = 0.03) in hypertensive patients. Co-infusion of the Nitric Oxide Synthase Inhibitor (L-NMMA)-blocked this venodilation, and the action was reversed with L-arginine. There were no significant changes in the arterial bed. CONCLUSIONS: Furosemide and torasemide induce a similar dose-response curve venodilation, but they have no effect on the arterial bed. Hypertensive patients show a smaller venous endothelium-dependent response than healthy controls. The venodilation induced by both diuretics requires release of nitric oxide.     

Diuretic action of the novel loop diuretic torasemide in the presence of angiotensin II or endothelin-1 in anaesthetized dogs.

The effects of torasemide (0.1 and 1 mg kg-1, i.v.) and furosemide (3 mg kg-1) on renal haemodynamics and excretory responses in the presence of angiotensin II and endothelin-1 was examined in anaesthetized dogs. Angiotensin II or endothelin-1 was continuously infused into the renal artery throughout the experiment and a bolus of torasemide or furosemide was injected into the bracheal vein. Continuous intrarenal arterial (i.r.a.) infusion of angiotensin II, at a dose of 5 ng kg-1 min-1, increased renal vascular resistance (RVR) and decreased renal blood flow (RBF) and glomerular filtration rate (GFR), but had no effect on systemic mean arterial pressure (MAP). Urinary excretion of sodium (UNaV) and urine flow (UF) were significantly decreased during angiotensin II infusion. Intravenous injections of torasemide in the presence of angiotensin II caused a dose-dependent increase in UF, UNaV and urinary excretion of potassium (UKV), while a decrease in RVR was accompanied by an increase in RBF. UKV was greater in the furosemide group than in the torasemide group, despite both groups having the same degree of aquaresis and natriuresis. Continuous i.r.a. infusion of endothelin-1, 1.5 ng kg-1 min-1, produced effects similar to those of angiotensin II on renal haemodynamics; however, the onset of action was extremely slow compared with the effects produced by angiotensin II. Endothelin-1 caused a significant decrease in UF, UNaV and UKV only at a later period, despite a relatively early depression of renal haemodynamics. Torasemide and furosemide also produced a sufficient diuretic action in this model.(ABSTRACT TRUNCATED AT 250 WORDS)     

Torasemide: a pharmacoeconomic review of its use in chronic heart failure.

Torasemide is a loop diuretic used for the treatment of hypertension and for oedema in chronic heart failure (CHF), renal failure and cirrhosis. The efficacy of torasemide in reducing salt and water retention in CHF has been established in double-blind comparative studies against furosemide. Torasemide has been shown to be at least as effective as furosemide in terms of total volume of urine excreted and also has a longer duration of action. The efficacy of torasemide (in terms of improved CHF symptoms and reduced pulmonary congestion, oedema and bodyweight) has been shown in randomised controlled trials and confirmed in large postmarketing studies. In addition, data from postmarketing studies have shown that patients receiving torasemide had significantly reduced hospital admission rates compared with patients receiving furosemide. Pharmacoeconomic assessments of torasemide have focused on its effect in reducing hospitalisation. Hospitalisation costs due to CHF decreased by 86% during the 11.2-month period of torasemide treatment, compared with the 6-month period prior to treatment, in a US retrospective study assessing medical and pharmacy claims data. Overall, average monthly costs for patients decreased by 56.6% after 5.1 months (from $US1,897.28 to $US823.70 per patient per month; PPPM), and by 76% after 11.2 months (from $US1,944.76 to $US470.76 PPPM) of torasemide treatment. In the furosemide group, average monthly costs for patients increased moderately from $US227.28 to $US261.18 PPPM after 12 months. Direct comparison of the torasemide and furosemide study groups was not possible because the group receiving torasemide had much higher healthcare resource use at baseline. Compared with furosemide, torasemide was associated with reduced rates of hospital admissions for CHF and/or cardiovascular causes in 3 studies, a retrospective analysis conducted in Germany, a prospective US study of patients enrolled from hospital admissions and a decision-analysis model. As a result, the direct costs of treatment for CHF or cardiovascular diseases for patients treated with torasemide were less than those with furosemide. However, in the US study, there was no statistically significant difference in hospital admissions for all causes and/or in overall direct medical costs, although the study was not powered to show this. In another US study of managed care patients with New York Heart Association (NYHA) class II or III CHF, no difference in clinical or economic outcomes was observed between patients taking torasemide or furosemide; despite the higher acquisition costs for torasemide, total costs were similar for both groups. Torasemide was found to be more cost effective than furosemide in terms of cost per patient with improved functional (NYHA) class of CHF severity in a retrospective German analysis, although this measure is not ideal. This study also evaluated indirect costs (for loss of productivity of employed patients) and resultssuggest torasemide has a favourable effect in reducing days off work compared with furosemide, although the population of employed patients in the study was very small. Torasemide has been shown to improve some measures of quality of life in 2 studies. It was associated with higher quality-of-life scores than furosemide in a 6-month study, but the differences were only significant at month 4. In another study, torasemide significantly improved fatigue, but full study details are yet to be published. CONCLUSIONS: Despite the higher acquisition cost of torasemide over furosemide, pharmacoeconomic analyses have shown that torasemide is likely to reduce overall treatment costs of CHF by reducing hospital admissions and readmissions. Torasemide has generally shown clinical and economic advantages over furosemide, although more long term data are needed to confirm these results and to further investigate effects on quality of life. There are limitations to the currently available pharmacoeconomic data, but present data support the use of torasemide as a first-line option for diuretic therapy in patients with CHF presenting with oedema and especially in those patients not achieving relief of symptoms with furosemide.     

Antihypertensive property of a novel uricosuric diuretic,S-8666, in rats

The antihypertensive, diuretic, and toxicological effects of S-8666 were studied in rats. At doses of more than 60 mg/kg/day, p.o., S-8666 was antihypertensive in DOCA-salt hypertensive rats with a potency corresponding to 1/20 of that of trichlormethiazide. The antihypertensive effect was dose-dependent, and, at the higher doses, S-8666 had a more potent depressor effect than trichlormethiazide. The antihypertensive activity of S-8666 was shown predominantly by the S-(?)-enantiomer, with the R-(+)-enantiomer being only slightly active. A similar dose-dependent antihypertensive effect was shown by furosemide, tienilic acid, or indacrinone, but the therapeutic index (LD₅₀/minimum effective dose) of S-8666 was the highest among them. The acute diuretic and natriuretic effects of S-8666 after oral administration of 60–200 mg/kg to DOCA-salt hypertensive rats correlated well with its antihypertensive effect, although such diuretic and natriuretic effects in normotensive rats had no effect on blood pressure. S-8666, like trichlormethiazide, showed a prophylactic effect on the development of hypertension in DOCA-salt hypertensive rats, salt-loaded spontaneously hypertensive rats (SHR), and salt-loaded Dahl-S rats, though it was much less potent. Moreover, the combination of S-8666 with captopril in SHR enhanced the depressor effect of captopril like hydrochlorothiazide. These results indicate that S-8666 can be an effective nonthiazide diuretic for use as an antihypertensive agent.     

Torasemide for the treatment of heart failure

Diuretics play an essential role in modern cardiovascular therapy, and are currently recommended for the treatment of congestive heart failure. Torasemide has been developed as a newer type of loop diuretic with a longer half-life, longer duration of action, and higher bioavailability compared to the most commonly used loop diuretic, furosemide. Torasemide also appears to have additional actions beyond the pure diuretic effect, such as anti-aldosterone effect and vasorelaxation effect. Studies have also investigated whether the superior pharmacokinetics and pharmacological activity of torasemide result in a favorable clinical outcome. Their results have indicated that, in comparison with furosemide, torasemide improves left ventricular function, reduces mortality as well as the frequency and duration of heart failure-related hospitalization, and improves quality of life, exercise tolerance and NYHA functional class in patients with congestive heart failure. Thus, torasemide appears to be a promising loop diuretic that contributes to a better management of patients with heart failure. Definitive clinical trials in a double-blind fashion are warranted.     

Diuretic profile of a novel loop diuretic torasemide in rats and dogs.

In the present study, the authors have examined the diuretic action of a novel loop diuretic torasemide and compared it to those of other diuretics, employing normal rats and dogs. Oral administration of torasemide elicited a dose-dependent increase in urine volume and electrolyte excretion, and elevated the urinary Na/K ratio in rats. These effects were more potent than those of the other diuretics furosemide, trichlormethiazide, indapamide and spironolactone. Moreover, torasemide exhibited a similar or higher urinary Na/K ratio than the combination of these diuretics and spironolactone. In a study employing anaesthetized dogs, i.v. injection of torasemide resulted in a higher urinary Na/K ratio in comparison to furosemide, in addition to potent and long-lasting diuretic activity.     

Renal effects of the high ceiling diuretic torasemide in rats and dogs

The mode of action of torasemide was investigated by clearance experiments in dogs and rats. In the dog, torasemide (1 mg/kg i.v.) had no significant effect on glomerular filtration rate (GFR) but increased p-aminohippuric acid (PAH) clearance by 16% (p less than 0.01). In the rat both GFR and PAH clearance were significantly decreased, on an average 8-17%, by torasemide infused in the dose range of 1 to 20 mg/kg i.v. After i.v. injection the onset of diuresis was observed within 5 to 10 min and peak effect within 20 to 40 min in the rat and within 40 to 60 min in the dog. Fractional water and sodium excretions of nearly 25% were obtained in the rat with a dose of 8 mg/kg i.v. At equipotent doses, torasemide and furosemide induced similar diuretic and natriuretic effects in function of time in the rat. In the dog the effects lasted much longer with torasemide than with furosemide. This difference can be related to the longer half-life (about 8 h) of torasemide in the dog. In both species significant differences could be noted between torasemide and furosemide with respect to the time course of their effects on the urinary excretion of potassium. From the first experimental hour on, torasemide proved to be significantly less kaliuretic than furosemide as shown by increased Na/K ratios, during the third experimental hour they reached 20.5 vs 9.9 in the dog and 11 vs 7.5 in the rat with torasemide and furosemide, respectively. In hydropenic dogs, free water reabsorption was significantly reduced with torasemide and osmolar clearance significantly increased.(ABSTRACT TRUNCATED AT 250 WORDS)     

托拉塞米注射液治疗儿童肾病综合征高度水肿的临床疗效观察

目的 探讨新型袢利尿剂托拉塞米注射液治疗儿童肾病综合征高度水肿的临床疗效.方法 对本科室2010年1月至2013年12月收治的肾病综合征患儿进行临床分析,将32例肾病综合征高度水肿患儿按随机数字表法分为托拉塞米组和呋塞米组,每组16例.两组在口服泼尼松足量[2 mg/（kg·d）或60 mg/（m^2·d）]治疗的基础上,托拉塞米组静脉滴注托拉塞米1～2 mg/（kg·d）,呋塞米组静脉滴注呋塞米1～2 mg/（kg·d）,疗程为5d.两组患儿分别于治疗前、治疗后第2、4、6d检测24 h尿量、体重、血液生化各项指标的变化情况,并记录不良反应.结果 托拉塞米与呋塞米两组患儿临床疗效比较,尿量均较治疗前明显增加,水肿消退,体重减轻,两组总有效率之间差异有统计学意义（94％ vs.81％; x2=3.023,P＜0.05）.呋塞米组患儿血钾浓度明显低于托拉塞米组（P＜0.05）,血尿酸明显高于托拉塞米组（P＜0.05）.结论 托拉塞米治疗儿童肾病综合征顽固性水肿,疗效显著,副作用小,对电解质及肾功能无明显影响,值得临床应用.     

Interaction of the diuretics torasemide and U-37883A with the KATP channel in rat isolated aorta

In this study we have investigated the interaction of the loop diuretics torasemide and furosemide and of the eukalemic diuretic U-37883A (4-morpholinocarboximidine-N–1-adamantyl-N’-cyclohexylhydrochloride) with the ATP-sensitive K⁺ channel (K_ATP channel) in rat aortic rings. Torasemide contains a sulphonylurea group which might enable the compound to interfere with K_ATP channels; this group is lacking in furosemide. U-37883A blocks several types of K_ATP channels. The interaction with the vascular K_ATP channel was probed in binding studies, ⁸⁶Rb⁺ efflux experiments and vasorelaxation assays. Torasemide inhibited the binding of the K_ATP channel inhibitor [³H]glibenclamide and of the opener [³H]P1075 with IC₅₀ values of 19 and 45 μM, respectively; furosemide and U-37883A were inactive or interfered with binding in a nonspecific way. In ⁸⁶Rb⁺ efflux experiments, the loop diuretics, at μM concentrations, inhibited basal tracer efflux to 50% whereas U-37883A had no effect. P1075-stimulated ⁸⁶Rb⁺ efflux, a qualitative measure of K_ATP channel opening, was inhibited by U-37883A and torasemide with IC₅₀ values of 0.06 and 130 μM, respectively; furosemide induced only a small (23%) inhibition. In experiments measuring isometric force, torasemide and furosemide partially relaxed endothelium-denuded aortic rings precontracted with noradrenaline or KCl with EC₅₀ values between 6 and 10 μM. The vasorelaxant effect of P1075 was inhibited in a noncompetitive manner by torasemide (300 μM) but unaffected by furosemide. U-37883A increased noradrenaline-induced force and inhibited the vasorelaxant effect of P1075 in an apparently competitive manner with an inhibition constant of 0.4 μM. The data show that torasemide interferes specifically with the binding of the K_ATP channel modulators [³H]glibenclamide and [³H]P1075 and with the K_ATP channel opening and vasorelaxant effects of P1075 whereas furosemide is inactive. This suggests that the interaction of torasemide with the vascular K_ATP channel is due to the sulphonylurea group present in torasemide. U-37883A, which does not inhibit P1075 binding, is one of the most potent blockers of P1075-induced ⁸⁶Rb⁺ efflux yet described but is relatively weak as an inhibitor of P1075-mediated vasorelaxation. The opposite vascular actions of torasemide and U-37883A are expected to contribute to the renal effects of these drugs. Received: 28 January 1998 / Accepted: 20 April 1998     

Renal effects of torasemide in the rat. Clearance and micropuncture studies

The effects of torasemide on renal glomerular and tubular functions were studied in rats using clearance and micropuncture techniques. A dose-response relationship of torasemide in the range of 0.2-20 mg/kg b.w. on the increase of urine volume, urinary sodium and potassium excretion was established. The effect of a dose of 0.2 mg/kg b.w. torasemide was completely abolished by preinjection of 10 mg/kg probenecid, whereas the effects of higher doses remained unchanged. Torasemide had no significant effect on glomerular filtration rate. Proximal fractional reabsorption was not influenced. A remarkable depression of fluid and electrolyte reabsorption, however, occurred in the loop of Henle after torasemide under free flow conditions, as well as in functionally isolated microperfused loops of Henle. No further inhibition of fluid and electrolyte reabsorption between the early distal convoluted tubules and the final urine could be detected. In contrast, a compensatory increase of reabsorption was observed in this part of the nephron. The activity of the tubuloglomerular feedback system was completely and reversibly blocked by torasemide. Torasemide did not differ from other typical loop diuretics with respect to the different renal actions studied here.     

托拉塞米治疗充血性心力衰竭的疗效及安全性的临床观察

目的：观察托拉塞米治疗充血性心力衰竭的临床疗效及安全性。方法：选取30例充血性心力衰竭患者,将其随机分为托拉塞米组与呋塞米组,在心力衰竭常规治疗方法一致的情况下,分别予托拉塞米与呋塞米20mg静推,治疗7d,记录两组患者治疗前后血压、血钾浓度、BNP值及EF值。结果：两组患者血压均有下降,但组间差异无统计学意义;托拉塞米组低血钾发生率更低,BNP下降且心功能改善更明显。结论：托拉塞米可一定程度改善心功能,低血钾及血压变化等不良反应较轻。     

Antihypertensive activity of the aqueous extract of Retama raetam Forssk. leaves in spontaneously hypertensive rats

The antihypertensive and diuretic effects of the aqueous extract of Retama raetam Forssk. (RR) leaves were studied in both normotensive (WKY) and spontaneously hypertensive rats (SHR). In SHR rats, daily oral administration of RR (20 mg/kg) for three weeks exhibited a significant reduction in blood pressure. The systolic blood pressure decreased significantly from the seventh day (P < 0.01) and persisted through the end of treatment (P < 0.001) in SHR rats. The RR significantly enhanced the diuresis in WKY rats (P < 0.001). Furthermore, oral administration of RR at a dose of 20 mg/kg produced a significant increase on urinary excretion of sodium (P < 0.05), potassium (P < 0.01) and chlorides (P < 0.01) in SHR rats. In WKY rats, RR treatment induced a significant increase on urinary potassium elimination (P < 0.05) without affecting sodium and chloride excretion. Irbesartan (Avapro) 20 mg/kg (body weight), an angiotensin II receptor antagonist, was used as reference drug. No significant changes were noted in heart rate after RR treatment in SHR as well as in WKY rats. Glomerular filtration rate showed a significant increase after RR administration in WKY rats (P < 0.01) and a no significant increase in SHR rats. These results suggest that oral administration of aqueous RR extract exhibited antihypertensive and diuretic effects in SHR rats and diuretic action in WKY rats.