Vasoactivity of trimetazidine on guinea-pig isolated ductus arteriosus

The acute effect of trimetazidine on the high frequency fatigue in the isolated Rat diaphragm muscle

The objective of this study was to determine the acute effect of trimetazidine (TMZ) on the pre-fatigue, fatigue and post-fatigue contractile characteristics and tension-frequency relationships of isolated rat diaphragm muscle. Muscle strips were taken from the ventral-costal aspects of the diaphragm muscle of rats killed by decapitation. The muscle strips were suspended in organ baths containing Krebs solution, with a gas mixture of 95% O2 and 5% CO2 at 37 degrees C and pH 7.35-7.45. After determining the thermoregulation and optimum muscle length the muscles were subjected to direct supramaximal stimulation with 0.05 Hz frequency square pulses for periods of 0.5 msec to obtain control values. After adding 5 x 10(-6) and 5 x 10(-5) M trimetazidine solution to the respective bath media, the contractile parameters of the muscles were recorded. The contractile parameters were also recorded for both the trimetazidine and trimetazidine-free media after application of the high frequency fatigue protocols. Later, the tension-frequency relationship was determined by applying stimulating pulses of 10, 20, 50 and 100 Hz to the muscle strips. Whilst the twitch tension obtained from the 5 x 10(-6) and 5 x 10(-5) M trimetazidine media showed numerical increases compared to that of the controls, these were not statistically significant (p>0.05). The contraction time exhibited a dose dependent increase (p<0.001), whilst the contraction and relaxation rates did not differ significantly. The isometric contraction forces obtained with the different stimulating frequencies showed a significant increase in the tetanic contraction only at 100 Hz (p<0.05). A comparison of the pre- and post-fatigue twitch tensions in the trimetazidine media showed the post- fatigue twitch tensions to be significantly higher than those of the pre-fatigue contraction forces (p<0.05). In the 5 x 10(-6) and 5 x 10(-5) M trimetazidine media the increases in the post-fatigue contraction force were 22 and 30%, respectively. These results demonstrated that in isolated rat diaphragm muscle, TMZ significantly limited the mechanical performance decrease during fatigue. It is our opinion that trimetazidine contributed to the observed fatigue tolerance by eliminating the factors of fatigue, due to preservation of intracellular calcium homeostasis, provision of the ATP energy levels needed by ATPase dependent pumps and especially by keeping the intracellular pH within certain limits.

Effects of trimetazidine and selenium on high-frequency fatigue in isolated rat diaphragm muscle

Trimetazidine (TMZ), which has been used in numerous experimental studies, is applied nowadays with the aim of reducing myocardial ischemia. The aim of this study was to determine the prefatigue and postfatigue contractile characteristics associated with the relationship between the force and frequency of contraction in muscle. The study was conducted using diaphragm muscle isolated from 40 male Wistar rats weighing 230 to 270 g. The rats were divided into 4 groups of 10 animals each: controls and TMZ-, selenium (Se)-, and TMZ+Se-treated groups. The rats in the control group were treated with 2 mL of physiologic serum (SF), those in the second group with Se 30 microg/kg in 2mL of SF, those in the third group with TMZ 5 mg/kg in 2 mL of SF, and those in the fourth group with a combination of TMZ 5 mg/kg + Se 30 microg/kg in 2 mL of SF. All rats were treated twice daily for 15 days by means of gastric lavage. The rats were then killed by cervical dislocation. The diaphragm muscle bands were removed and placed in an organ bath. After a 2-hour thermoregulatory period, muscles were fatigued with 5-ms pulses at a frequency of 40 Hz. Force-frequency relationships were studied after the application of 10, 50, and 100 Hz and the development of contraction curves. Contraction forces for the groups treated with TMZ, Se, and TMZ+Se (16.1 +/- 1.2, 13.2 +/- 1.3, and 14.9 +/- 1.0 g, respectively) were significantly lower than for the control group (17.0 +/- 1.4 g) during the prefatigue period (P<.001). Similarly, postfatigue contraction forces for the treated groups (15.7 +/- 1.3, 8.8 +/- 1.0, and 12.0 +/- 1.4 g, respectively) were significantly lower than for the control group (12.4 +/- 1.2 g, P<.001, P<.001, and P<.05, respectively). A significant decrease was noted in postfatigue contraction forces and contraction and relaxation rates in the Se- and TMZ+Se-treated groups compared with prefatigue values (P<.001), but the difference was not significant. Force-frequency relationships were evaluated at 10, 50, and 100 Hz. The tetanic contraction forces for the control, Se-, TMZ-, and TMZ+Se-treated groups at 100 Hz were 81.3 +/- 5.7, 91.6 +/- 6.8, 65.3 +/- 5.0, and 84.9 +/- 7.5 g, respectively. In the TMZ-treated group, a significant increase was observed in tetanic contraction forces at 100 Hz compared with controls (P<.001); no significant changes were seen in the force-frequency relationships at 10 and 50 Hz. The decrease in the contraction force in the postfatigue period was prevented to a larger extent in the TMZ-treated group than in the TMZ+Se- and Se-treated groups.

Pharmacological manipulation of acute cyclosporin ischemic renal injury with trimetazidine

Cyclosporin has had a major impact on organ transplantation, but associated nephrotoxicity is a significant problem. Renal hypothermia, a known anti-ischemic maneuver, limits cyclosporin-ischemic renal failure. Pharmacological manipulation with an anti-ischemic agent, such as trimetazidine, may prevent cyclosporin nephrotoxicity. We tested this hypothesis in a canine single kidney model of cyclosporin-enhanced ischemic renal failure. Trimetazidine treatment was associated with significantly better biochemical and histological markers of renal function and structure. Trimetazidine may have a role to play in protecting against cyclosporin nephrotoxicity in clinical renal transplantation.

Effects of trimetazidine on in vivo coronary arterial platelet thrombosis

We used Folts' model of critical coronary artery stenosis with endothelial damage, which measures platelet-rich thrombus accumulation from cyclic flow reductions (CFRs). This paper reports results applied to trimetazidine, a member of the piperazine group. Trimetazidine at a dose of 1 mg/kg completely abolished CFRs caused by accumulating thrombus in the circumflex coronary artery in 4 of 8 open-chest anesthetized beagles. More trimetazidine (up to 5 mg/kg) abolished CFRs in two more and attenuated them in the remaining two dogs. There were no systemic hemodynamic effects observed. Adrenaline was then infused to stimulate platelet activation. At a rate of 0.4 microgram/kg/min, CFRs were restored in one dog only. Adrenaline given at 1.6 micrograms/kg/min resulted in restoration or increase in the slope of CFRs in all animals. A further six nonoperated dogs were anesthetized and given trimetazidine 3 mg/kg. Routine coagulation studies were not altered. However, aspirin 5 mg/kg significantly increased bleeding time, whereas trimetazidine alone did not. These findings suggest that trimetazidine is effective in preventing intracoronary platelet aggregation in this model. Because of its demonstrated sparing of coagulation factors and its lack of effect on bleeding time, the cause is unlikely to be inhibition of the fibrinogen or thrombin receptors, or interference with arachidonic acid metabolism.

Effect of phenazine methosulfate on electrophysiological activity of the semicircular canal: antioxidant properties of trimetazidine

Ischemia strokes appear to be the main source of cochleo-vestibular dysfunctions of peripheral origin. The present study aimed to investigate the action of oxygen free radicals on the bioelectric activity of the labyrinthine epithelium, using the frog semicircular canal as an in vitro preparation. We also examined the possible effect of the antianginal drug, trimetazidine (TMZ), under physiological conditions and during the administration of phenazine methosulfate (PMS). The model allows the ionic composition of endolymphatic and perilymphatic fluids bathing the semicircular canal to be dealt with separately. Spontaneous afferent vestibular nerve activity and the endolymphatic potential were recorded under resting conditions. Three additional parameters were investigated during mechanical displacement of the endolymphatic fluid: the ampullar direct current, the nerve direct current and the frequency of the evoked afferent spikes. Addition of TMZ (10(-6) and 10(-5) M, 50 min) into the perilymphatic compartment did not induce significant modifications of the different bioelectrical signals. Generation of oxygen free radicals, through administration of PMS (10(-5) M, 15 min) into the perilymphatic compartment, caused an impairment of all bioelectrical signals, except the ampullar direct current. The spontaneous activity, nerve direct current and frequency of afferent evoked spikes signals were significantly reduced 75 min after the start of PMS administration (-64, -17 and -32%, respectively). In contrast, there was a marked increase of the endolymphatic potential signal (+51%). Addition of TMZ (10(-6) or 10(-5) M) into the perilymph solution reversed the effect of PMS on all bioelectrical signals. These results indicate that TMZ acts as an antioxidant molecule which is capable of protecting the labyrinthine epithelium from the deleterious effect of oxygen radicals. Our data suggest that the protective effect of TMZ on ischemia-induced cochleo-vestibular dysfunctions may be accounted for by the antioxidant properties of this antianginal drug.

Beneficial effects of trimetazidine on mitochondrial function and superoxide production in the cardiac muscle of monocrotaline-treated rats

The administration of a single dose of monocrotaline (105 mg/kg) after 21 days produced in rats a reduction of cardiac mitochondrial function at the level of complexes I, II and IV of the respiratory chain, associated with the formation of heart hypertrophy, prevalently of the right ventricle. Moreover, in these rats, the submitochondrial particles produced more O2- and in the cardiac tissue there was an elevation of malondialdehyde content. The repeated administration of trimetazidine (5 mg/kg/24 hr) improved the cardiac mitochondrial function, particularly in state 3 of respiration. In addition, the treatment with trimetazidine reduced, in the heart muscle, both the production of mitochondrial O2- and the content of tissue malondialdehyde. Trimetazidine added alone did not significantly change either the cardiac mitochondrial activity, or the mitochondrial O2- production in comparison to control rats. Also, the content of tissue malondialdehyde was not modified by the repeated administration of trimetazidine. In all the experimental conditions examined, the content of cardiac water-soluble fluorescence substrates did not significantly change in comparison to control rats.

Acute effects of trimetazidine evaluated by exercise testing

A single dose of 60 mg trimetazidine (the normal daily dose) improved exercise capacity in angina pectoris, as reflected by an increase in the duration of exercise, total work performed, and improvement in ECG signs of ischaemia. All these effects occurred without any detectable chronotropic or vasomotor effect. The importance of this study is to demonstrate that these beneficial effects, already well-recognized after chronic administration of 20 mg three times a day, also occur after a single administration equivalent to the normal daily dose.