[Propargylglycine restores endothelium-dependent relaxation of aortic smooth muscles in old rats].

In the study we investigated the effect of blockade cystathionine-gamma -lyase (CSE), an enzyme of hydrogen sulfide (H2S) (de novo) synthesis on the endothelium-dependent relaxation of aortic smooth muscle (SM) in old rats. It has been shown that an inhibition of CSE by propargylglycine (PAG) results in restoration of a decreased ACh-induced relaxation of aorta in old rats. This effect of PAG was removed by blocking nitric oxide (NO) synthesis in the endothelial cells.

[Magnetic-laser influence on the system of nitric oxide and contractile activity of smooth muscles of rat aorta under hypertension].

The study was conducted on three groups of rats: Group I included Wistar rats with normal blood pressure (first control group); group II - rats with genetically determined hypertension (second control group); group Ill - rats with genetically determined hypertension under the influence ofmagnetic-laser power (study group). For the low-intensively magnetic-laser influence (MLI) we have used device MIT-MT, Ukraine, which was designed for the treatment of low-frequency magnetic field using optical flow blue and red ranges of spectrum. The MLI duration was 15 minutes for the blue range, and 25 minutes for the red one.

[The effect of hydrogen sulfide on contractile activity of the vascular smooth muscles in rats].

The effect of endogenous and exogenous hydrogen sulfide (H2S) on contractile activity of vascular smooth muscle (VSM) was studied. The introduction of substrate synthesis H2S L-cysteine and its donor NaHS in vitro caused concentration-dependent relaxation of VSM of aorta and portal vein. Low concentrations of hydrogen sulfide donor (10(-5) mol/L) caused vasoconstriction of both types of the vessels.

[Changes of vascular reactivity and reactive oxygen species in conditions of varying duration of permanent stay in the alienation zone in mice].

Peculiarities of changes in the vascular reactivity and in the content of reactive forms of oxygen and stable metabolites of nitric oxide (NO) were studied in the aorta preparations of C57BL/6 and BALB/c mice of the two age groups (6 and 18 mo.), which were born and permanently kept in the Chernobyl alienation zone. The results obtained showed a disturbance of acetylcholine-induced endothelium-dependent reactions of relaxation of smooth muscles of the thoracic aorta.

[Vascular reactivity and metabolism of the reactive oxygen species and nitrogen in effects of low doses of radiation].

The disturbance of endothelium-dependent and endothelium-independent vascular reactions of relaxation was registered in the preparations of aorta of radiosensitive BALB/c mice, exposed to chronic external gamma-irradiation (cumulative dose of 0.43 Sv). Low doses of radiation induced an intensive hydrolysis of membrane phospholipids by phospholipase A2, displayed by an increase in the level of eukosanoisds--LTC4 and TxB2, formed under effects of lipid oxidases (lipoxygenase and cyclooxygenase) at the same time with O2 generation.

[Effect of enalapril on nitric oxide synthesis, oxidative metabolism, and vascular tone in aging rats].

Endothelium-dependent and endothelium-independent reactions of relaxations of vascular smooth muscle (VSM) were examined in the aorta preparations of the two groups (6-8 and 21-22 month). The studies also two NO synthase (NOS) isoform activity--inducible (iNOS) and constitutive (cNOS), activity of arginase and nitrate reductase and the content of high-molecular nitrosothiols (HMNT) and low-molecular nitrosothiols (LMNT) and stable metabolites of NO (NO(-)2, NO(-)3). Aging rats demonstrated only endothelium-dependent responses of VSM to acethylcholine lowering.

[Influence of enalapryl on vasomotor reactions of rats with chronic deficiency of dopamine in the mesencephalo-striatal system].

The results of experiments on isolated preparations of aorta and portal vein of rats with chronic deficiency of mesencephalo-striatal dopamine have shown that endothelium-dependent reactions of dilatation were inhibited. If rats with dopamine deficiency received enalapryl (20 mg/kg) these reactions partly recovered. A possible conclusion may be that in conditions of cerebral dopamine deficiency the functional state of endothelium got worse, and endothelium-dependent dilatation of vascular smooth muscles was inhibited.

[Age-related characteristics of contractile vascular reactions and the content of oxygen free radicals and nitric oxide metabolites in BALB/c mice in conditions of alienation zone].

Peculiarities of changes of the endothelium-dependent and endothelium-independent vascular reactions of relaxation, and the content of oxygen free radicals and stable metabolites of nitric oxide (NO) were studied in the aorta preparations of BALB/c mice of the two age groups (6 and 18 months), which were born and lived in the Chernobyl alienation zone. The results obtained showed no endothelium-dependent reactions of aortal smooth muscles relaxation to acetylcholine and only partially impaired endothelium-independent reactions to sodium nitroprusside in animals of both age groups. There was a significant decrease in the content of high-molecular nitrosothiols (HMNT) in old animals, which may signify a depletion of NO depot in the aorta.

[Inhibitors of arginase pathway in L-arginine metabolism as a new class of antihypertensive drugs: action of urea on oxidative and nonoxidative metabolism of L-arginine and vascular tone in chronic hypertension].

It has been studied an action of chronic urea introduction (40 mg/kg, 14 and 28 days) as arginase inhibitor on nonoxidative (arginase activity, urea, polyamines content) and oxidative (NOS activity, nitrite- and nitrate-anion content) metabolism of L-arginine in aorta, heart, plasma and erythrocytes of SHR. It has been shown that urea is an inhibitor of not arginase only, but also ornitinedecarboxilase (ODK) reactions, limiting L-arginine consumption for urea and polyamines synthesis and thus facilitating its utilization for nitric oxide synthesis by NOS. These exogenous effects of urea are not accompanied by amelioration of tissue ischaemization within cardiovascular system.

[Endothelium-dependent contractile reactions of vascular smooth muscles and content of oxygen free radicals in aging rats].

Endothelium-dependent and endothelium-independent reactions of vascular smooth muscles were studied in isolated preparations of thoracic part of aorta and portal vein of rats of two age groups--6.8 mo. (control) and 24-26 mo.

[Inhibitors of arginase in the L-arginine metabolic pathway as a new class of antihypertensive drugs: effect of carbamide on lipid oxidative metabolism and on vessel tonus during arterial hypertension].

Have studied action of chronic urea--an arginase inhibitor--introduction (40 mg/kg, 28 days) on blood pressure, endothelium-dependent reactions of aorta smooth muscle cells (SMC) and nonenzymatic (contents of diene conjugates and H2O2) and enzymatic (contents of free arachidonic acid and vasoconstrictic eicosanoids LTC4 and TXA2) oxidizing lipid metabolism of heart, aorta, plasma and erythrocytes of spontaneously hypertensive rats. Have shown, that urea down regulate blood pressure without any normalization of endothelium-dependent reactions of SMC of aorta and down regulate both enzymatic and nonenzymatic oxidizing lipid metabolism. Down regulation of two alternative (by cyclooxygenase and by lipoxygenase) enzymatic pathways of free arachidonic acid oxidizing metabolism by urea can be one of mechanisms of its antihypertensive action.

[Disorders of endothelium-dependent vascular reactions and of the arginase and NO-synthase pathways of L-arginine metabolism in arterial hypertension].

In normotensive rats (NTR) and spontaneously hypertensive rats (SHR) with high (subgroup 1) and low (subgroup 2) level of the systemic arterial pressure (SAP) we studied an activity of arginase and nitric oxide synthase (NOS) in different tissues, and the content of their metabolites: urea and nitrit anion (NO2-). In isolated preparations of a thoracic aorta we recorded endothelium-dependent (ED) dilator reactions on acetylcholine (Ach). It has been found that in heart, aorta, plasma and erythrocytes of rats (subgroup 2) both the activity of arginase and content of urea increase remarkably.

[The nitric oxide system in a chronic deficiency of mesostriatal dopamine: the action of nitroglycerin].

Unilateral chronic deficiency in dopamine was induced by injection of the neurotoxin 6-hydroxydopamine into the mesostriatum of male Wistar rats (n = 15). The content of the nitric oxide metabolite--NO2- was three time less than in controls in the neostriatum on the operated side only, whereas, in the heart, aorta and plasma it was reduced by 1.9, 1.

[The nitrous oxide system under conditions of chronic cerebral dopamine deficiency and hypoxia].

Acute experiments were conducted on adult Wistar rats two months after unilateral microinjection of the 6-hydroxydopamine into the medial forebrain bundle. This led to a greater than 90% decrease of dopamine, fell by 70% of the content of the stable metabolite of nitric oxide-nitrite anion and by up to 80% of nitric oxide synthase activity in the lesioned neostriatum. Nitric oxide synthase activity fell by 30% in the heart, by 60% in the aorta, while nitrite anion decreased in the heart and aorta, in blood plasma and erythrocytes by 45%, 40%, 70%, 30% compared with controls rats, respectively.

[The role of the endothelium and of biologically active substances of endothelial origin in regulating blood circulation and cardiac activity].

The role of endothelium and its biologically active derivatives in the central and local control of circulation is under consideration. Molecular and cellular mechanisms of the activation of the endothelium-dependent responses of different functional significance are being discussed, as well as the state of endothelial responses in the development and compensation of pathological processes in the cardiovascular system.

[Characteristics of the contractile reactions of rhythmically active vascular smooth muscles in spontaneously hypertensive rats undergoing hyperoxygenation and the role of the endothelium in their development].

Experiments on isolated preparations of the portal vein from healthy and spontaneously hypertensive rats have revealed that removal of the endothelium has no influence on hyperoxygenation-induced increase in the contractile activity of vascular smooth muscles (VSM). It is also shown that VSM from hypertensive rats demonstrate higher sensitivity to hyperoxygenation than VSM from healthy rats. Results of the study confirm a supposition that contractile effect of hyperoxygenation on VSM is realized mainly via direct influence of oxygen on plasma membranes of VSM and increase of the membrane permeability for extracellular Ca2+.

[Endothelial modulation of arterial smooth muscle reactions to biological amines and electrical stimulation].

The effects of 5-hydroxytryptamine (5-HT), noradrenaline (NA), acetylcholine (Ach), ATP and electrical stimulation (ES) were studied in isolated porcine epicardial coronary artery and the rat thoracic aorta preparations. A dose-dependent contraction of vascular smooth muscle (VSM) segments with endothelium in response to biological amines (10(-7)-10(-5) M) and ES (2-16 Hz, 20 msec, 50 V) was demonstrated. Removal of the endothelium abolished the dilatory effect of the ATP (10(-5) M), Ach (10(-7) M), but potentiated the constrictor responses of the VSM to 5-HT, NA, ES.

[Cellular mechanisms of transitory smooth muscle contraction of the coronary arteries during hypoxia: role of intracellular Ca2+].

In experiments on isolated porcine and canine coronary artery rings it was shown that vascular smooth muscle (VSM) during hypoxia (decreasing bath PO2 with 147 to 20-15 mm Hg) response to biphasic constriction-dilation reaction. Transient hypoxic contractions (THC) of VSM preserved completely in Ca2+-free solution and partially (up 50-60%) in the presence of Ca2+-channel blockers, but abolished by procaine. THC of VSM skinned by saponin significantly depressed at depletion of Ca2+-store sarcoplasmic reticulum (SR) by caffeine nd abolished after SR destruction.

[Magnesium ions and contractile activity of vascular smooth muscle cells in hypoxia].

In isolated smooth muscle of the rat portal vein removal of Mg2+ from perfusate induced rapid enhancement of frequency and amplitude of spontaneous contractions and decreased inhibiting effect of hypoxia on the smooth muscle contractile activity. Concomitant elevation of extracellular Ca2+ has no additional protective effect on the smooth muscle in hypoxia. Ten-fold lowering of Mg2+ content in buffer solution resulted in a significant rise in the tension of the smooth muscle activated by Ca2+.

[Mechanisms of endothelium-dependent transient contraction of coronary artery smooth muscles during hypo-oxygenation].

The effect of endothelium on hypo-oxygenation--induced reactions of preactivated smooth muscle (SM) of the canine and porcine large coronary arteries, was studied. Decreased oxygenation of Krebs--bicarbonate solution (PO2-26.6-19.

[Role of the endothelium in the development of the contractile reactions of vascular smooth muscle during decreased oxygenation].

Noradrenaline-preactivated vascular smooth muscles (VSM) of the rat thoracic aorta showed two-phase reactions in response to decreased oxygenation: significant relaxation was preceded by transient constriction. When the endothelium was removed only VSM relaxation phase was retained, with no constriction observed. The data obtained suggest an endothelium-dependent nature of VSM constriction reaction to hypoxia, in contrast to endothelium-independent VSM relaxation.

[Effect of restricted oxygenation of vascular smooth muscles on the contractile effects of direct electrical and mechanical stimulation].

Contractility reactions of the smooth muscles of the rat portal vein and the umbilical vein of man to direct electrical stimulation and rapid stretch were examined under different PO2 levels in perfusate. It was shown that during perfusion of vascular preparations with oxygenated Krebs solution, the active myogenic responses to rapid stretch and contractility reactions to electrical stimulation are well pronounced and dependent on the stimulation intensity. The decrease in perfusate PO2 is accompanied by a considerably less increment of the amplitude of spontaneous contractions and tonic tension of the smooth muscles in response to direct mechanical and electrical stimulation, respectively.