[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.

[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.

[Activation of free-radical processes as a factor of ionizing radiation-induced changes in contractile activity of a vascular wall]. / Aktyvatsiia vilnoradykalnykh protseciv iak faktor porushennia skorochuvalnoi aktyvnosti sudynnoi stinky pid diieiu ionizuiuchoi radiatsii.

The influence of ionizing irradiation (1, 2 and 4 Gy 137Cs) on both the activity of free-radical processes in plasma, formed elements and aorta wall as well as on the character of contractile vascular reactions of isolated rings of thoracic aorta and carotid artery in rabbits has been studied. The experiments were carried out on the 7th day after the whole-body irradiation. The results indicate that simultaneously with the weakening of antioxidant mechanisms both endothelium-dependent and endothelium-independent vascular wall relaxation slightly decreases after 1 Gy exposure. Noradrenaline and KCI-induced contraction is shown to increase. However, these changes are not statistically significant. Irradiation in dose of 2 and 4 Gy considerably decreases endothelium-dependent relaxation. Nitroglycerin-induced relaxation greatly diminishes, KCI- and noradrenaline-induced constriction considerably increases in these conditions. The level of activation of free-radical processes considerably increases too. Thus, already on the 7th day after irradiation significant changes in reactivity of vascular wall are developed. Radiation injures both endothelium and vascular smooth muscle cells. The free-radical processes seem to be the main cause of radiation vascular damage, so there is a pronounced correlation between the changes of vascular contractile properties and the degree of activation of these processes.

[The vascular protective effect of the combined administration of magnesium chloride and antioxidants in prolonged hypercholesterolemia ]. / Angioprotektorna efectyvnist poiednanogo vykorystannia khlorystogo magniiu ta antyoksydantiv v umovakh tryvaloi giperkholesterynemii.

The angioprotective efficacy of combined application of magnesium chloride and antioxidants during prolonged hypercholesterolemia has been investigated on the experimental model of atherosclerosis in rabbits. The application of magnesium chloride and acetate tocopherol from the very beginning of the atherogenic diet is shown to exert a pronounced angioprotective effect preventing the development of structural and functional changes in the aorta wall. If the treatment is initiated against the background of the well developed atherosclerotic symptoms, its efficacy is less pronounced but remains still on a quite high level. These data indicate that combination of magnesium chloride and antioxidants has not only protective action but can also induce partial regression of the developed atherosclerotic changes.