[The endothelium-derived hyperpolarization factor as a reserve defence mechanism of vasodilatation under conditions of ionizing radiation].

The goal of this study was to determine the cellular mechanisms of vascular endothelial dysfunction in rats irradiated with gamma-rays. Acetylcholine (Ach)-induced relaxation of rat thoracic aorta rings was measured as a test of endothelial integrity and function. The data obtained allow suggest that endothelial function is impaired in aorta from g-irradiated rats mainly due to the loss of EDRF/NO-dependent, but not EDHF-dependent relaxation. It has been shown that r-irradiation reduced the Ach-induced NO-release measured as nitrite anion content. Experiments on isolated rat aortic smooth muscle cells using whole-cell patch clamp technique demonstrated that irradiation led to a significant decrease in outward potassium currents. However, gamma-ray irradiation was without effect on K(+)-current carried through apamine-sensitive channels while the current through charybdotoxin-sensitive channels was increased as compared to cells from control animals. The data suggest that EDHF is resistant to ionized radiation and may constitute a crucial reserve mechanism for maintenance of blood flow under radiation. Therefore, it is likely that the subsequent studies related to EDHF identification will be important for new drugs development and targeted pharmacological intervention at endothelium dysfunction in case of radiation impact.

[Effect of radiation on calcium-dependent pathway of nitroglycerin-evoked relaxation of rat aorta].

The effects of nitroglycerine (NG, 10(-7)-10(-4) M) on contractile force and intracellular calcium concentration ([Ca2+]i) in deendotelized thoracic aorta smooth muscles (SM) precontracted with high K+ in control and gamma-irradiated rats (6 Gy) were investigated. NG-induced activation of soluble guanylate cyclase (sGC) as dominating pathway of NG-induced SM relaxation without related decrease in [Ca2+]i level is demonstrated. Radiation was without effect on this sGC-dependent and [Ca2+]i -independent NG-induced relaxation of vascular smooth muscle but decreased the basal levels of[Ca2+]i by (28.4 +/- 11.9)% (6 Gy, 9th-day).

[Functional and molecular changes of large-conductance calcium-dependent potassium in rat aortic smooth muscle cells after ionizing irradiation].

The effects of whole body gamma-irradiation on large conductance Ca(2+)-activated K+ channels (BK(Ca)) function and mRNA expression in rat thoracic aorta smooth muscle cells (SMCs) were studied using combined patch-clamp technique in whole-cell modification and RT-PCR analysis. The stimulation of control SMCs by increasingly depolarized voltage steps showed clearly expressed outward K+ currents in control SMCs. Outward currents in SMCs obtained from irradiated animals on the 9th and 30th days post-irradiation demonstrated a significant decrease of K current density amplitudes. Paxillin was without effect on irradiated cells on 30th day post-irradiation indicating the absence of conductance through BK(Ca) channels. The results of RT-PCR analysis showed that expression both alpha-subunit and beta1-subunit of BK(Ca) channels appears to be considerably diminished on 30th day post-irradiation. It is likely that radiation-induced malfunction functional activity of channels is related with insufficient expression of BK(Ca) structural elements in SMCs. In conclusion, the data obtained clearly demonstrate that decreased of the BK(Ca) channels alpha- and beta1-subunit expression in SMCs is a key factor of abnormality in BK(Ca) channels activity. This abnormality may contribute to vasorelaxing force depression following non-fatal whole-body gamma-irradiation.

[Effect of ionising irradiation on outward potassium current in the aorta smooth muscle cells in rats: the role of protein kinase C].

It is known that gamma-irradiation leads to vascular hyperfunction and hypertension development. In this study we tested the hypothesis that ionizing irradiation directly affects vascular smooth muscle cells due to damage in outward K+ channel function. The goal of this study was to evaluate the influence of whole-body ionizing irradiation (6 Gy dose) on Ca(2+) dependent K+ channels and to clarify a possible involvement of protein kinase C in this process. Experiments were conducted on isolated rat aorta smooth muscle cells using whole-cell patch clamp technique. It has been shown that the basic component of outward K+ current in rat aortic smooth muscle cells is a large conductance Ca(2+)-activated K+ current (BK(Ca)). BK(Ca) currents in smooth muscle cells obtained from irradiated animals on the 9th and 30th days post-irradiation demonstrated a significant decrease of K(+)-current density amplitudes. Protein kinase C inhibitor, chelerythrine, effectively restored BK(Ca) current reduced by ionizing irradiation. In conclusion, the results suggest that gamma-irradiation suppressed BK(Ca) current in vascular smooth muscle cells, and this effect is mainly due to activation of protein kinase C.

[Modern conception of protein kinase C role in the vascular smooth muscles tone regulation].

Protein kinase C is an important regulatory enzyme that plays significant role in the vascular tone regulation. Protein kinase C is involved in the vascular smooth muscle cells (SMC) contractility at physiological conditions and its hyperreactivity at different types of pathology. Myogenic and endothelium-dependent pathways of protein kinase C-mediated vascular tone regulation include a variety of cellular mechanisms. The most important protein kinase C-mediated mechanisms in SMC are the increase of myophilament Ca2+-sensitivity; regulation of plasmolema ion permeability, and proliferative changes in SMC. Protein kinase C-related mechanisms in vascular endotheliocytes include regulation of formation and transduction of humoral and electrical signals to SMC that play an important role in the pathological vasospasm development.

[Mechanisms of nitric oxide activity in cardiovascular system as a basis of pathogenetic therapy of related diseases]. / Fundamental'ni mekhanizmy diï oksydu azotu na sertsevo-sudynnu systemu iak osnovy patohenetychnoho likuvannia ïï zakhvoriuvan'.

General characteristics and mechanisms of effects of nitric oxide (NO) and its role in the development of pathology are reviewed. Presented are the data about NO participation in the regulation of circulation and cardiovascular system; NO-dependent mechanism of regulation of cardiovascular reactivity against the background of dysfunction of endothelium; cGMP-independent mechanism of NO effect upon Ca homeostasis and the sensitivity of myofibrils of smooth muscle cells to Ca ions; pharmacological correction of disturbances of NO metabolism and related endothelial dysfunction; role of age changes of the endothelial function in the development of cardiovascular pathology.

[Effect of inhibition of glycolysis and myoendothelial electrical coupling on contractile responses of pulmonary artery and aorta during hypoxia in rats]. / Vplyv blokady hlikolizu ta mioendotelial'noho elektrychnoho zv'iazku na rozvytok skorotlyvykh reaktsii stinky lehenevykh arterii ta aorty shchuriv pid diieiu hipoksiï.

The effects of blockade of glycolysis on the contractile activity of isolated vascular rings of both the pulmonary artery and, the thoracic aorta were studied under hypoxia in intact, denuded vessels and those with blocked myoendothelial electrical coupling. The blockade of glycolysis led to a reversion of a hypoxic contraction in the pulmonary artery but had no effect on hypoxic dilatation of the aorta. Hypoxic constriction of the pulmonary artery was abolished after denudation and stayed unchanged at the following blockade of glycolysis. Moreover, blockade of glycolysis had no effect on the hypoxic responses of the pulmonary artery after blockade of the myoendothelial gap junctions. The data suggest that hypoxic contraction of the pulmonary artery is endothelium-dependent, in contrast to the hypoxic dilatation of the aorta. It is likely that glycolysis in endothelial cells and myoendothelial gap junctions contribute to hypoxic pulmonary vasoconstriction due to formation and conduction the depolarizing electrical signals from endothelial cells to smooth muscles causing their contraction under hypoxia.

[Effect of inhibiting protein kinase C on calcium sensitivity of contractile apparatus of vascular smooth muscle during vasospasms of different origins]. / Vplyv blokady proteïnkinazy C na zminy kal'tsiievoï chutlyvosti skorotlyvoho aparatu sudynnykh gladen'kykh m'iaziv pry vazospastychnykh stanakh riznogo henezu.

The aim of the study was to investigate the role of protein kinase C (PKC) in changes in myofilament Ca(2+)-sensitivity of vascular smooth muscle cells (SMC) in rats at different vasospastic states: hypoxic pulmonary vasoconstriction, genetically determined hypertension, and hypertension resulted from ionizing radiation. All vasospastic states demonstrated rightward shifts in pCa-tension curves suggesting that myofilament Ca(2+)-sensitivity had increased. In chemically (beta-escin) skinned pulmonary artery, hypoxia-induced increase in myofilament Ca(2+)-sensitivity was completely abolished by PKC inhibitor chelerythrine. The similar results were demonstrated in skinned aorta SMC of spontaneously hypertensive rats where an increase in myofilament Ca(2+)-sensitivity was also abolished by PKC inhibitors chelerythrine and staurosporine. The chelerythrine partially inhibited myofilament Ca(2+)-sensitivity that had increased following gamma-radiation. The data suggest the key role of PKC activity in modulation of myofilament Ca(2+)-sensitivity in SMC. We conclude that PKC-mediated increase in myofilament Ca(2+)-sensitivity is one of the main mechanisms which contribute to the vasospasm of different genesis.

[Current concepts on the mechanisms of hypoxic effects on vascular tonus]. / Suchasni uiavlennia pro mekhanizmy vplyvu hipoksiï na tonus krovonosnykh sudyn.

It is well known that hypoxia causes smooth muscle relaxation of the majority of mammalian systemic blood vessels, whereas smooth muscles in the pulmonary and large coronary arteries constrict under hypoxia. The review describes a modern concept of the mechanisms involved in the hypoxic vasoconstriction and vasodilatation. Cationic channels of a plasma membrane, the contractile apparatus, and mitochondria are the main oxygen sensors in the vascular smooth muscle cells. Hypoxic vasodilatation is mediated mainly by a decrease in the voltage-dependent Ca2+ entry, decrease in Ca2+ sensitivity of the contractile apparatus, and activation of ATP-dependent K+ channels. This process also involves endothelium derived nitric oxide. Hypoxic vasoconstriction mechanisms may be related to voltage-gating K+ channels inhibition, Ca2+ release from intracellular stores and inactivation of Ca2+ activated K+ channels each of them leads to increase in intracellular Ca2+ concentration. Platelet-activating factor, prostaglandins F2 alpha, E2, tromboxan B2, leucotriens C4 and D4 also contribute to hypoxic vasoconstriction. Glycolysis which intensity increases in hypoxia, and electron transport chain which generates the reactive oxygen species play the important role in the development of hypoxic pulmonary vasoconstriction. They possess the ability to change redox state in the cells and therefore to modulate the activity of the cationic channels. Hypoxia also leads to a proliferation of smooth muscles in the vascular wall. Better understanding of the underlying hypoxia-related mechanisms is vital for the explanation of enhanced blood flow under hypoxia, and is absolutely necessary for creating new effective antihypoxic drugs.

[Change in contractile vascular function in arterial hypertension of different genesis and its correction with phosphatidylcholine liposomes]. / Skorochuval'na funktsiia sudyn pry arterial'nii hipertenzïi riznoho henezu ta ïï korektsiia za dopomohoiu fosfatydylkholinovykh liposom.

We examined the effects of phosphatidylcholine liposomes (PCL) upon the contractile vascular dysfunction in spontaneously hypertensive rats (SHR) and gamma-irradiated (60Co, 6 Gy) rats and rabbits. A significant impairment of endothelium-dependent relaxation was evident in both SHR and irradiated animals. An important novel finding of these experiments is that the impairment was mainly due to the loss of NO-dependent component of relaxation, with the component of relaxation mediated by EDHF being preserved. PCL were found to restore endothelium-dependent relaxation in both SHR and the irradiated vascular tissues. It is important to note that irradiated animals exhibited distinct and sustained signs of hypertension (blood pressure (BP) increased from 122 +/- 8 to 185 +/- 6 mm Hg). Being administered in a single dose of 30 mg/kg, 1 h after irradiation, PCL prevented hypertension development in an early post-irradiated period (9 days). At a later post-irradiated period (6 months), PCL in the single dose lost such a protective effect. Single administration of PCL in SHR led to a transient decrease in BP, but their repeated daily administration caused a persistent decrease in BP up to its normalization as early as in 4 days. These results suggest that PCL possess hypotensive activities due to their ability to normalize endothelial function.

[cGMP-independent effect of nitric oxide on contractility and intracellular calcium level of rat tail artery vascular smooth muscles]. / tsHMF-nezalezhnyi vplyv oksydu azotu na skorotlyvu aktyvnist' i vmist vnutrishn'oklitynnoho Ca(2+) hladen'kykh m'iaziv khvostovoï arteriï shchura.

The effects of nitric oxide (NO, 10(-6) M) on contractility and intracellular calcium level ([Ca2+]i) of rat tail artery smooth muscles in control and under inhibition of soluble guanylate cyclase (sGC) with 6-anilino-5,8-quinolinedione (LY83583, 10(-6) M) are investigated. NO-induced relaxations of vascular smooth muscles comprised 61.01 +/- 5.56% of maximum induced amplitude of K(+)-contracture, and decreases in [Ca2+]i comprised 66.35 +/- 11.33%. Under the inhibition of sGC with LY83583 NO-induced relaxations of vascular smooth muscles comprised 29.41 +/- 5.17% of maximum induced amplitude of K(+)-contracture, and decreases in [Ca2+]i comprised 53.68 +/- 16.93%. Thus, cGMP-independent relaxation of vascular smooth muscle and decrease in [Ca2+]i of rat tail artery is confirmed.

[The role of the endothelium and of biologically active substances of endothelial origin in regulating blood circulation and cardiac activity]. / Rol' endoteliiu ta biolohichno aktyvnykh rechovyn endotelial'noho pokhodzhennia v rehuliatsiï krovoobihu i diial'nosti sertsia.

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.

[Endothelium-dependent vascular response in rabbits during prolonged experimental hypercholesterolemia]. / Endotelii-zalezhni sudynni reaktsii u krolykiv pid chas tryvaloi éksperymentalnoi hiperkholesterynemii.

It was shown in experiments on anesthetized rabbits that disturbances in endothelium-dependent relaxant (Ach-induced) and constrictor (hypoxia-induced) vascular responses depended on duration of high hypercholesterol diet and on the structural damage of the vascular wall as well as on changes in the functional activity of endotheliocytes. Short (1 month) hypercholesterolemia led to thickening of the blood-cellular barrier and promoted a decrease in the endothelium-dependent relaxant response to Ach. At the same time short hypercholesterolemia enhanced a constrictor component of the vascular smooth muscle (VSM) response to hypoxia. It may be explained by a different degree in disturbance of synthesis and/or release of the endothelial relaxing and constrictor factors. At the later period of hypercholesterolemia (2-9 month) parallel with a pronounced damage of the endothelium and development of atheromatous plaques, the impairment of the endothelium-dependent vascular responses became more and more pronounced. As a rule, Ach-induced relaxation in VSM was registered in sole experiments only and very often was either absent or transformed to contraction. Constrictor components of vascular response to hypoxia were significantly decreased as well. The above-mentioned disbalance between endothelial relaxant and constrictor factors in combination with structural damage of the endothelium and difficulty in transendothelial transport of these factors to effector elements of the vascular wall may cause vasospastic reactions in VSM at atherosclerosis.