(+)-Catechin Stereoisomer and Gallate Induce Oxidative Stress in Rat Aorta.

The goal of the work was to study changes in the activity of the angiotensin-converting enzyme (ACE) and production of reactive oxygen species (ROS) in the aorta of rats after the intraperitoneal injection of stereoisomers of catechin and gallate. The activity of ACE in the aorta sections was determined by measuring the hydrolysis of hippuryl-l-histidyl-l-leucine. The production of ROS in the aorta sections was estimated from the oxidation of dichlorodihydrofluorescein.

Black tea is more effective than green tea in prevention of radiation-induced oxidative stress in the aorta of rats.

In the work, the effect of black tea on oxidative stress induced in the aorta by irradiation was studied. The efficiency of black and green tea types was compared, and the effect of the main green tea components (-)-epigallocatechin galate (EGCG) and (-)-epigallocatechin (EGC) on the aorta was studied. The activity of ACE in rat aorta segments was determined by measuring the hydrolysis of hippuryl-L-histidyl-L-leucine, and the production of ROS was estimated from the oxidation of dichlorodihydrofluorescein.

Flavonoids decrease the radiation-induced increase in the activity of the angiotensin-converting enzyme in rat aorta.

The basic factor of cardiovascular diseases is atherosclerosis, which is due largely to an increase in the activity of the angiotensin-converting enzyme (ACE) in vessels. Flavonoids diminish the risk of cardiovascular diseases and the flavonoid taxifolin normalizes the activity of ACE. We examined the efficiency of seven flavonoids in preventing an increase in ACE activity in aorta of rats exposed to ionizing radiation.

Effects of taxifolin on the activity of angiotensin-converting enzyme and reactive oxygen and nitrogen species in the aorta of aging rats and rats treated with the nitric oxide synthase inhibitor and dexamethasone.

The action of taxifolin on the angiotensin-converting enzyme (ACE) and the formation of reactive oxygen and nitrogen species (ROS/RNS) in the aorta of aging rats and rats treated with nitric oxide synthase inhibitor (N ω-nitro-L-arginine methyl ester (L-NAME)) or dexamethasone have been studied. The ACE activity in aorta sections was determined by measuring the hydrolysis of hippuryl-L-histidyl-L-leucine, and the ROS/RNS production was measured by oxidation of dichlorodihydrofluorescein. It was shown that taxifolin at a dose of 30-100 μg/kg/day decreases the ACE activity in the aorta of aging rats and of rats treated with L-NAME or dexamethasone to the level of the ACE activity in young control rats.

Low doses of ethanol decrease the activity of the angiotensin-converting enzyme in the aorta of aging rats and rats treated with a nitric oxide synthase inhibitor and dexamethasone.

In the present study, the activity of ACE (angiotensin-converting enzyme) in the aorta of senescent rats and rats treated with the NOS (NO synthase) inhibitor L-NAME (NG-nitro-L-arginine methyl ester) or dexamethasone and the effect of low doses of ethanol (0.2-1.2 g/kg of body weight, daily for 8-12 days) on this activity were studied.

Distribution of the activity of the angiotensin-converting enzyme in the rat aorta and changes in the activity with aging and by the action of L-NAME.

The activity of the angiotensin-converting enzyme (ACE) of the inner surface (the endothelium surface) of rat aorta sections has been studied depending on their distance from the aortic arch, age of rats, and the duration of treatment of rats with the NO synthase inhibitor, N (ω)-nitro-L-arginine (L-NAME). The activity of ACE of aorta sections was determined by measuring the hydrolysis of hippuryl-L-histidyl-L-leucine and was expressed as picomoles of Hip-His-Leu hydrolyzed per minute per square millimeter of the endothelium surface. It was found that the ACE activity considerably varies along the aorta of young rats.

Modification of multidrug resistance of tumor cells by ionizing radiation.

Purpose: The effect of ionizing radiation on multidrug resistance (MDR) of human larynx cancer HEp-2 cells has been investigated. We studied the dependence of the radiation effect on radiation dose, time after irradiation and cell density.

Methods: MDR was determined from an increase in cell sensitivity to daunorubicin, taxol and vincristine by the inhibitors of multidrug resistance cyclosporin A and avermectin B(1), and from the suppression by cyclosporin A of the transport of rhodamine 123 out of the cells.

Antitumor effect of avermectins.

The effect of a mixture of naturally occurring aversectin C and avermectin B(1) on the growth of ascites and solid experimental tumors of mice was studied. It was shown for the first time that avermectins possess a pronounced antitumor action. When added at nontoxic doses, they significantly suppressed the growth of ascites Ehrlich carcinoma and P388 lympholeukemia and solid Ehrlich and 755 carcinomata.

Avermectins inhibit multidrug resistance of tumor cells.

The modification of the sensitivity of Hep-2 and P388 tumor cells to taxol and vincristine, substrates of multidrug resistance proteins, by naturally occurring avermectins and the effect of avermectins on the accumulation of calcein in cells and the efflux of rhodamine 123 were studied. While avermectins did not affect the sensitivity of tumor cells to hydrogen peroxide and cisplatin, they significantly enhanced the sensitivity of cells of both wild-type and resistant strains to taxol and vincristine. The coefficients of modification for resistant strains were substantially higher.