[The modulation of mitochondrial pore sensitivity of isolated myocardial preparations to the action of phenylarsenoxide].

In the experiments with coperfused isolated ring strips from a. carotis (A) and trabecule (T) from the right auricle of guinea pigs it has been shown the modification of a sensitivity of mitochondrial pore (MP) to the action of its activators. Exogenous NO-donor-sodium nitroprusside and hypoxic precondition (HP) caused a protective action on myocardium and arterial vessels isolated preparations of the old animals due to reducing of a myocardium MP sensitivity. While the contractile response to control electric stimulation T and A of the trained animals was almost twice lower in comparison to the group untraining ones, which can be evidence of the resources depleted of myocardium and vessels preparations caused by hypoxic training of the old animals.

[Early marker of myocardial injury of the ischemia-reperfused heart in dogs and during operations with artificial circulation in humans].

The model of ischemia/reperfusion was reproduced on 9 unconscious dogs. Simultaneously with registration of indexes heart work, hemodynamic and mitochondrial factor (MF) in venous blood from right atrium was defined. Measures were done by spectrophotometria. We have also performed spectrophotometric determination of MF in 11 patients in course of operation with blood cardioplegia. Samples of mixed venous blood from the right atrium were taken on different stages of artificial blood circulation: ischemia and reperfusion. Besides that, patients' level of enzymes was defined: creatine kinase (CK), mv-creatine kinase (mv-CK), lactatedehydrogenase (LDG), aspartataminotransferase (AST), within first day of postoperative period, and also ECG-recording within pre- and after operative period were done. Maximal MF level correlates with frequency and severity of cardiac rhythm disturbance, severity of myocardial hypoxia (r = 0.81). Maximum MF level also demonstrated correlation with KK (r = 0.97), mvKK (r = 0.92), LDG(r = 0.81), AST (r = 0.85). Thus, in experimental and clinic conditions myocardial ischemia was accompanied by mPTP activation, which led to reperfusion myocardial injuries and to release of MF. Method of MF determination gives opportunity to propose its usage as early marker of ischemic injuries and also as marker of mPTP opening in vivo.

[Study of mithochondrial permeability transition pore in the development of myocardial and vascular contractility disfunctions].

In experiments on the isolated myocardial and vascular preparations the role of the mithochondrial permiability transition pore (mPTP) in the development of reperfusion injury was investigated. Co-perfusion of the previously activated myocardial trabecula (MT) and arterial rings (AR) by solution collected during the first 5 min of isolated heart reperfusion, caused a sharp and significant decrease of tonic tension of both isolated preparations. Besides the significant inhibition of the MT and AR reactions after electrical stimulation, modulation of AR reaction by the influence of MT is also registered. The solution collected at first minutes of heart reperfusion, preserve a dilation property within 24 hours of storage at room temperature. Preliminary perfusion of MT and AR with methylen blue (MB, 10(-4) M/l) or the addition to the solution dithiothreitol (DTT, 2 x 10(-5) M/l) and diethyl maleate (DEM, 2 x 10(-5) M/l) resulted in an almost complete inhibition of this dilatation influence on the isolated preparations. The data received testify that the solution comprise a NO-containing substance, possible nitrosoglutation. Pre-incubation (2 min) MT in a solution with mPTP activator phenylarsine oxide (PAO, 10(-5) M/l) and subsequent reperfusion with a control solution resulted in deep and irreversible decrease of tonic tension and inhibition of contractility of both isolated preparations. The received data are qualitatively similar to results described above. Our data and results received in additional experiments on isolated mitochondria allow us to assert that solution flowing from the ischemized heart contains the stable mitochondrial factor (SMF) with a significant dilatation property. An addition of MB and DEM in the reperfusion solution abrogated its dilation influence. Co-perfusion (10 min) of the injured MT and AR by the solution with nitrosoglutation (10 (-5) M/l) restored normal contractility of the isolated preparations and modulation of the AR reaction by the influence of MT. It once again confirms the presence of an NO-containing substance in the SMF content. Thus, the mPTP activation plays the key role in the development ofmyocardial reperfusion injury and results in release of SMF, which can be the basic agent of paracrine regulation of myocardial contractility, coronary and peripheral vessels tone.

[Effect of nitric oxide on the efficiency of oxygen consumption by the working skeletal muscle in fatigue].

The influence of NO on the efficiency of oxygen usage by a skeletal muscle under fatigue of dog's gastrocnemius muscle was investigated. In control experiments was shown, that 10 short-term (30") electrical stimulation (8 Hz, 5 ms, 20 V) with 5" interval resulted in significant reduction of the muscle contraction force (more than 40%) and increased considerably oxygen cost of muscle gastrocnemius work (more than 130%) compared to the initial parameters. The registered depression of the muscle contraction force testified to development of gastrocnemius muscle fatigue, accompanied by mitochondrial factor (MF) appearance in blood from femoralis vein, which, as shown by us earlier, is a marker of the mPTP opening. Injection of L-NMMA, a NOS inhibitor (2.7 mg/kg, i.a.) resulted in pronounced fall (more than 1.5 times) of the initial force parameters, in comparison with the control experiments. Under these conditions the magnitude of oxygen cost of gastrocnemius muscle work exceeded control parameters considerably. The development of gastrocnemius muscle fatigue under L-NMMA action was accompanied, as well as in the control condition by the mPTP opening. The preliminary injection of sodium nitroprusside, a NO donor (0.2 mg/kg, i.v.) prevented a fall of muscle contractions force and considerable inhibition of oxygen usage efficiency by gastrocnemius muscle under conditions similar to control. Furthemore, gastrocnemius muscle fatigue was not developed, and MF concentration in blood from femoralis vein was much lower, than in the control experiments, that testified to absence of the mPTP opening. Apparently, preliminary short-term (30") electrical stimulation (8 Hz, 5 ms, 20 V) with 2' interval, created the precondition effect and raised the level of authentic NO. Under these conditions, as well as under preliminary injection of the NO donor, we did not register the marked inhibition of oxygen usage efficiency and development of gastrocnemius muscle fatigue. At the same time, MF in blood from v. femoralis was practically absent, that testify to absence of the mPTP opening. Thus, NO in physiological concentration by inhibition of mPTP opening, can prevent decrease of oxygen usage efficiency and development of the working skeletal muscle fatigue.

[Role of nitric oxide and mitochondrial permeability pore in changes of oxygen consumption in the working skeletal muscle]. / Rol' oksydu azotu ta mitokhondrial'noï pory v zmini kysnevykh rezhymiv pratsiuiuchoho skeletnoho m'iaza.

On anaesthetized dogs the role NO and mitochondrial permeability transition pore (MPTP) in the regulation of regional blood circulation, efficiency of oxygen using, and muscle contraction force was investigated. Under different frequency stimulation it was shown, that short-term (30") smoothly tetanic contraction (40 Hz) is more economic for a skeletal muscle than short-term (30") single contractions (8 Hz) with respect to the efficiency of oxygen using. Injection NOS inhibitor L-NMMA (2.7 mg/kg, i.a.) resulted in pronounced fall of a functional hyperemia magnitude (P < 0.01), significant reduction of the muscle contractions force (P < 0.01), and efficiency of oxygen using (P < 0.01), in m.gastrocnemicus, in comparison with control. Pretreatment with an exogenous activator of MPTP phenilarsine oxide (PAO, 0.2 mg/kg, i.a.) caused a marked inhibition of an endothelium-dependent vessels dilation on skin-muscle region of rear limb. At the same time the muscle contractions force was significantly decreased (P < 0.01) and efficiency of oxygen using was diminished too (P < 0.01). This was accompanied by an appearance in blood from v. femoralis mitochondrial factor (MF), indicating MPTP activation. Preliminary injection of the exogenous NO donor sodium nitroprusside (0.2 mg/kg, i.v.) prevented considerably an inhibition of a dilation vessels reserve, a fall of muscle contractions force (P < 0.01) and considerably reduced oxygen cost (P < 0.01) of a m.gastercnemicus work also. The concentration of MF in blood from v. femoralis also was considerably reduced (P < 0.001) that has been the evidence of MPTP inhibition. Thus, activation of MPTP and development of oxidative stress resulted in endothelium dysfunction, a force of muscle contraction diminishing and a significant decrease in efficiency of oxygen using. NO essentially reduced the negative effects of MPTP activation and was antagonist of oxidative damages development.

[The role of the mitochondrial permeability transition pore in the development of skeletal muscle fatigue in dogs]. / Rol' mitokhondrial'noï pory v rozvytku stomlennia skeletnoho m'iaza sobaky.

On anaesthetized dogs the role of the mitochondrial permeability transition pore (mPTP) in the development of the m. gastrocnemius fatigue was investigated. In a control series of experiments it was shown, that 10 short-term (30") electrical stimulation (8 Hz, 5 ms, 20 V) with 5" interval resulted in significant reduction of the muscle contractions force (more than 40%) and considerably increased oxygen cost of a m. gastrocnemicus work (more than 130%), comparison with initial parameters. The registered inhibition of the muscle contraction force pointed on the development of m. gastrocnemius fatigue, that was accompanied by an appearance in blood from v. femoralis mitochondrial factor (MF), which, as shown by us earlier, is a marker of the mPTP opening. Preliminary injection of selective inhibitor of the mPTP opening cyclosporine A (0.012 mg/kg, i.v.) resulted in the pronounced fall of the MF concentration in blood from v. femoralis, in comparison with the parameters registered under control conditions. Pretreatment with the another inhibitor of the mPTP opening melatonin (0.75 mg/kg, i.v.) prevented inhibition of the muscle contractions force and reduction of the efficiency of oxygen using by m. gastercnemicus under conditions similar control. Thus, m. gastercnemius fatigue didn't develop, and the MF concentration in blood from v. femoralis was much lower, than in the control, that testified to absence of the mPTP opening. So then, fatigue development was accompanied by inhibition of the muscle contractions force, marked reduction of the efficiency of oxygen using by m.gastercnemicus that was prevented by the mPTP opening inhibitors. Thus, the mPTP opening can underlie the development of the working skeletal muscle fatigue.

[Determination of the stable mitochondrial factor in vivo]. / Vyznachennia stabil'noho faktora mitokhondrial'noho pokhodzhennia in vivo.

We have determined a release of a stable mitochondrial factor (SMF) into the outflowing blood in vivo. That effect was induced by ischemia/reperfusion or phenylarsin oxide (PAO)--the activators of the mitochondrial permeability transition pore (MPTP) and the oxidative stress. The SMF was measured by a spectrophotometer in the range of wave-lengths 230-260 nm with the absorption maximum of 240-250 nm. The SMF release was accompanied with a decrease in the myocardial contractility, disturbances in cardiodynamics and regional blood circulation. The data obtained have demonstrated that the SMF can be used as a marker of MPTP opening in vivo.