Effects of 1,2,3,4-tetrahydroimidazo[4,5-c]-pyridine derivatives on ethanol oxidation by alcohol dehydrogenase isoforms from human liver.

We studied in vitro effects of four 1,2,3,4-tetrahydroimidazo[4,5-c]-pyridine derivatives formed in the reaction of the corresponding aldehydes with histidine on the rate of ethanol oxidation by alcohol dehydrogenase isoforms from human liver. None of test compounds inhibited ethanol oxidation by these enzymes. Some of them increased alcohol dehydrogenase activity to 220-240% of the initial level. Only one test compound accelerated ethanol oxidation by b1b2-alcohol dehydrogenase (150% of the control). The molecular mechanism underlying these effects of 1,2,3,4-tetrahydroimidazo[4,5-c]-pyridine derivatives on ethanol oxidation by alcohol dehydrogenase isoforms from human liver is discussed.

[The structure of the leukocyte DNA in leukemia patients during chemotherapy]. / Struktura DNK leikotsitov bol'nykh leikozom v protsesse khimioterapii.

The authors studied the degree of DNA damage in in vitro cultured human peripheral lymphocytes (PL) and Jurcat's human T-cell lymphoma cells exposed to a stabilized 4 OH-cyclophosphan-mamophosphatide (MA) derivative, as well as in the leukocytes from patients with leukemia who were treated with cyclophosphan. There was an increase in alkaline DNA denaturation rate of LP lysates and T-cell lymphoma cells, which was in proportion to MA concentrations, and a higher sensitivity of LP to the genotoxic effect of MA given in doses of 5-10 micrograms/ml than that of Jurcat's cells, as well as high peripheral lymphocyte and neutrophil DNA damages in patients with leukemia during chemotherapy. The authors consider that the accumulation of single-strand breaks and alkaline-labile sites, which was recorded from the increase in alkaline DNA denaturation rate of cell lysates, is a highly sensitive test for detecting DNA damages in resting and slowly proliferating cells and can be useful in revealing and evaluating the severity of human genotoxic effects.

[Comparative study of the effectiveness of the classical and modified Cooper protocol for breast cancer chemotherapy]. / Sravnitel'noe issledovanie éffektivnosti klassicheskoi i modifitsirovannoi skhem Kupera pri khimioterapii raka molochnoi zhelezy.

Efficiency of routine and modified Cuper procedures was studied after evaluation in saliva and urine of women with mammary gland tumor of the following parametres: alterations in dynamics of acrolein excretion with saliva, dynamics of alterations in calculated therapeutic doses of cyclophosphane administered using these procedures, dynamics of the ratio between non-metabolized cyclophosphane and its initial level in urine of the patients. Analysis of the data obtained suggest that the liver tissue enzymatic systems, involving in biotransformation of cyclophosphane, were distinctly less impaired during the modified Cuper procedure as compared with the routine course, thus corroborating advantages of the modified procedure used in chemotherapy of patients with mammary gland tumor.

NADPH-dependent reduction of amaranch in liver microsomes characterized the quantity of low spin forms of cytochrome P-450.

We confirmed that NADPH-dependent anaerobic amaranch reduction in rat liver microsomes is compatible with the interaction of the dye with Fe(III) heme of cytochrome P-450 as the type II substrate. This process is rate-limiting in the whole reaction. High positive correlation (r = 0.949) between the values of Vmax for reaction of NADPH-dependent anaerobic amaranch reduction and the relative content low spin forms of cytochrome P-450 determined by ESR in microsomes from liver of control and induced by PB, BP, IS and 4-MP rats was observed. Relative content of low spin forms of cytochrome P-450 determined by ESR was increased according to BP less than PB less than control less than IS approximately 4-MP; Vmax values increased according to BP less than PB less than control less than IS less than 4-MP. Thus, reaction of NADPH-dependent anaerobic amaranch reduction may be used for determination of low spin forms of cytochrome P-450 at physiological conditions.

[The effect of finoptin on the metabolism and pharmacological action of cyclophosphane in vivo and in vitro]. / Vliianie finoptina na metabolizm i farmakologicheskoe deistvie tsiklofosfana in vivo i in vitro.

Phynoptin (Ph) and cyclophosphamide (CP) gave rise to a type I spectral changes with liver microsomal fraction. KS were 15 microM and 2150 microM, respectively. Ph increases the concentration of NBP product(s) of CP and acrolein in the blood plasma of animals. Ph increases a toxicity of CP. LD50 was 388.0 +/- 13.9 mg/kg for CP and LD50 was 342.8 +/- 16.9 mg/kg for CP in combination with Ph. Ph changes a therapeutic action of CP in mice with hemocytoblastosis La. Pharmacokinetic interactions have been demonstrated between calcium antagonists Ph and CP.

[Oxidation of cytochrome b5 reduced by ascorbic acid]. / Issledovanie reaktsii okisleniia tsitokhroma b5, vosstanovlennogo askorbinovoi kislotoi.

The steady-state levels of aerobic and anaerobic reduction of cytochrome b5 by ascorbic acid and the initial rates of cytochrome b5 reduction in the presence of ascorbic acid and of anaerobic cytochrome P-450 reduction in the presence of NADH were used to calculate the rate constants for cytochrome b5 oxidation. The rate constant for cytochrome b5 autooxidation in the membrane is equal to that for isolated cytochrome b5, i. e., 5 X 10(-3) s-1 (37 degrees C). The rate constant for the second cytochrome b5 oxidation reaction in the membrane, i. e., electron transfer to cytochrome P-450, is equal to 140 X 10(-3) s-1 (37 degrees C).

Reconstitution of liver monooxygenase system in solution from cytochrome P-450 and NADPH-specific flavoprotein monomers.

Microsomal monooxygenase system was reconstituted in the presence of non-ionic detergent Emulgen 913 from cytochrome P-450 and NADPH-specific flavoprotein isolated from phenobarbital-induced rabbit liver microsomes. At Emulgen 913 concentration of 0.05 g/l mixed complex between flavoprotein and cytochrome was formed with 5: 5 protein molar ratio and molecular weight of 700 kD. The 2-hour incubation of the enzymes with 0.25 g/l Emulgen 913 at 4 degrees C was accompanied by dissociation of protein oligomers to monomers. The reconstituted systems containing flavoprotein and cytochrome as mixed complexes or monomers were able to catalyze NADPH-dependent cytochrome P-450 reduction and benzphetamine N-demethylation. Taking into consideration the effective concentrations of the enzymes the apparent second order rate constants of these reactions with monomers were 100 times those with complexes.

[Reconstitution of the monooxygenase system in a solution and in an immobilized phospholipid layer]. / Rekonstruktsiia monooksigenaznoi sistemy v rastvore i v immobilizovannom sloe fosfolipida.

To clarify the molecular organization of NADH- and NADPH-dependent microsomal redox systems their isolated purified carriers were incorporated into immobilized azolectin layer with a higher viscosity than that of the liposomes. It was shown that the NADH-cytochrome c reductase activity characterizing the NADH-cytochrome b5 reductase and cytochrome b5 interaction sharply decreased in the immobilized system as compared to that in solution. However, the activity of hydroxylase reactions catalyzed by immobilized NADPH-cytochrome P-450 reductase and cytochrome P-450 was the same as in solution. This, the reconstitution in the immobilized phospholipid layer allowed to characterize NADH-cytochrome b5 reductase as a system operating on occasional collisions of its components. On the contrary, the diffusion of the NADPH-dependent redox chain carriers was not the rate-limiting step of the reaction.