[Hemoglobin oxidation and erythrocyte hemolysis induced by a synthetic analog of alpha-tocopherol not containing an isoprenoid chain]. / Okislenie gemoglobina i gemoliz éritrotsitov, indutsiruemye sinteticheskim analogom al'fa-tokoferola, ne soderzhashchim izoprenoidnoi tsepi.

The effect of alpha-tocopherol and its synthetic analogue which does not contain an isoprenoid chain, 2,2,5,7,8-pentamethyl-6-hydroxychroman (chromanol), on rat erythrocyte and hemoglobin has been studied. Chromanol, unlike alpha-tocopherol, induces oxidation of hemoglobin into aquomethemoglobin and causes erythrocyte hemolysis. A mechanism of the reaction has been established. It consists of two-electron reduction of haem-associated oxygen molecule. The products formed can cause oxidative membrane damage and subsequent hemolysis. The absence of similar activity of alpha-tocopherol seems to be connected with the inaccessibility of ligand sphere of hemin iron because of the presence of the isoprenoid chain. The oxidative activity of chromanol can explain the absence of E-vitamin activity in this compound.

[The role of isoprenoid chain of alpha-tocopherol in the protection of synaptosomes against lipid peroxidation and phospholipase A2-induced damage]. / Rol' izoprenoidnoi tsepi alpha-tokoferola v zashchite sinaptosom ot perekisnogo okisleniia lipidov i deistviia fosfolipazy A2.

The role of the alpha-tocopherol molecule isoprenoid chain in synaptosomal membrane protection from lipid peroxidation activation and phospholipase A2 damage was investigated. A comparative study of alpha-tocopherol analogs differing in the length of the isoprenoid chain revealed that the increase in the chain length results in a decrease of the efficiency of inhibition in the course of synaptosomal lipid peroxidation activation. This effect is due to the diminution of mobility of chromanols in the lipid bilayer which is associated with an increase in the length of the isoprenoid fragment. The decreased efficiency of lipid peroxidation inhibition resulting from the lengthening of the chromanol nucleus phytol chain is concomitant with the appearance of new stabilizing properties, e. g., the ability to protect synaptosomal membranes from the damaging action of phospholipase A2. This effect is lost with a decrease in the length of the chromanol isoprenoid chain.

PUVA-induced erythema and changes in mechanoelectrical properties of skin. Inhibition by tocopherols.

Influence of antioxidants on two phototoxic effects of 8-methoxypsoralen (8-MOP) was studied: erythema and changes in mechanoelectrical properties of skin. alpha-Tocopherol and its analogs with shortened lateral hydrocarbon chains at C2-atoms of chromane groups (chromanols) were used as antioxidants. alpha-Tocopherol and its analogs inhibited both phototoxic effects of 8-MOP. Inhibition was observed only if antioxidants were present in skin during irradiation. When applied after irradiation these antioxidants produce no inhibitory effect. The antioxidant antierythemal action depends greatly on their concentration. The protective effects is maximal at antioxidant concentrations 2.5 . 10(-10) - 5 . 10(-9) mol . cm-2 of skin, at concentrations higher than 5 . 10(-9) mol . cm-2 the protective action is decreased. The protective effect of antioxidants depends on the irradiation dose.

[Effect of lateral wick chain of tocopherols on oxidative reactions in lipids]. / O vliianii bokovoi fitil'noi tsepi tokoferolov na okislitel'nye reaktsii, protekaiushchie v lipidakh.

An injection of a alpha-tocopherol and analog devoid of the lateral chain (C1) at a dose of 90 mg/kg of body weight to experimental animals increases the levels of natural antioxidants and lipid oxidation in mouse liver 4- and 4.5-fold, respectively. The effects of alpha-tocopherol on the lipids possessing a high antiradical activity and containing the lateral chain and that of its analog, C1, also possessing a high antiradical activity but devoid of the lateral chain, were compared. The similarity of alpha-tocopherol and its analog effects on the lipids can be due to their antiradical properties. The degree of this effect is, however, different, which can be accounted for by possible fixation of the molecular in the membrane due to the presence of the lateral chain and a resulting increase of antioxidant concentration in the lipids.

[Allosteric regulation of glucosamine synthetase activity by naphthoquinone derivatives and ethyl ester of di-(4-oxycumarinyl-3)-acetic acid]. / Allostericheskaia reguliatsiia aktivnosti gliukozaminsintetazy proizvodnymi naftokhinona i etilovym efirom di-(4-oksikumarinil-3)-i uksusnoi kisloty.

The effects of derivatives of naphthoquinone, e.g. 2-methyl-3-phytyl-1,4-naphthoquinone (vitamin K1), 2-methyl-1,4-naphthoquinone (vitamin K3), 3-dihydro-2-methyl-1,4-naphthoquinone-2-sodium sulfonate (vicasol), derivatives of naphthohydroxyquinone, e.g. 2-methyl-1,4-naphthohydroxyquinone 1-monoacetate, 2-methyl-1,4-naphthohydroxyquinone 1,4-diacetate and the oxycumarine derivative di-(4-oxycumarinyl-3)-acetate ethyl ester (pelentan) on the activity of purified glutamine synthetase (EC 5.3.1.19) from rat liver were studied. The enzyme activity was increased under effects of vitamins K1 and K3 and was inhibited by pelentan. The data obtained are indicative of the allosteric effect of these compounds on the enzyme.