Induction of cytochrome P450 1A1 in rat liver slices by 7-ethoxycoumarin and 4-methyl-7-ethoxycoumarin.

7-Ethoxycoumarin (EC) is widely used as a model substrate for monooxygenase function, its O-deethylation representing cytochrome P450 (P450) activity mainly of 1A but also of 2B isoforms. Reports on investigations of its own capacity to induce or suppress P450 activities, however, have not been found in biomedical literature. To avoid the influence of in vivo pharmacokinetics, studies can well be undertaken with liver slice incubation. Therefore in the present investigation precision-cut rat liver slices from male 43-63-day-old male HAN:Wistar outbred rats were incubated at 30 degrees C in carbogen saturated William's Medium E for 24 h. EC was added previously to final concentrations of 10, 25, 50, 75 or 100 microM. After incubation, homogenate was prepared from slices and used for model reactions (7-ethoxyresorufin O-deethylation [EROD] and 7-pentoxyresorufin O-depentylation [PROD]). EROD, indicating activities of 1A isoforms, was enhanced by incubation with EC at 25 and 50 microM to about doublefold but showed control or lower values at 75 and 100 microM. Incubation with beta-naphthoflavone in comparison led to variable increases (3-5-fold of controls). For PROD as an indicator of the phenobarbital inducible P450 isoforms 2B1 and 2B2 no enhancement was found, but a decrease by incubation with 75 and 100 microM EC. To further investigate the correlation between enzyme activity and gene expression after slice incubation, P450 1A1 mRNA content was measured by RT-PCR. Induced gene expression for 1A1 was seen with different EC concentrations to a variable extent, though not as strong as with BNF. Similar incubation with 4-methyl-7-ethoxycoumarin revealed an even stronger induction of EROD activity with maxima at about 10-32 microM, reaching BNF values. In contrast incubation with 7-benzyloxycoumarin had no evident inducing or suppressing effect, neither on EROD nor on PROD activity.

Protective effects of vitamin E and C on cisplatin nephrotoxicity in developing rats.

The kinetics of vitamin E was followed in serum, liver and kidney of 10- and 55-day-old rats after the administration of a single i.m. dose of 100 mg alpha-tocopherol acetate/100 g body wt. The basal levels without vitamin E administration were significantly higher in serum and liver of 10- than 55-day-old rats. The effect of vitamin E on cisplatin (CP; 0.6 mg/100 g body wt., i.p.) nephrotoxicity was investigated by determining urinary volume and protein excretion, as well as the concentration of blood urea nitrogen (BUN) and lipid peroxides in renal tissue (LPO). Previously described age differences in CP nephrotoxicity were confirmed. The administration of vitamin E, 12 h prior to CP, diminished the toxic effect of CP in young and adult rats. This effect could not be enhanced by a second administration of vitamin E. The simultaneous administration of vitamin E and C 12 h prior to CP intensified the protective effect of a single administration of vitamin E in 10- and 55-day-old rats without influencing the concentration of platinum in renal tissue.

[The study of the in vitro effect of selenium on formation of active oxygen species and lipid peroxidation in rat liver microsomes]. / Izuchenie vliianiia selena in vitro na obrazovanie aktivnykh form kisloroda i perekisnoe okislenie lipidov v mikrosomakh pecheni krys.

In vitro influence of sodium selenite on cytochrome P-450-dependent formation of active oxygen species on lipid peroxidation (LPO) in rat liver microsomes was studied. Sodium selenite (10(-6)-10(-3) M) did not influence rates of NADPH/Fe-induced formation of active oxygen species (O2.-, OH., H2O2) and NAPDH-dependent LPO. Only at 10(-3) M selenite caused significant decrease in production of hydrogen peroxide in microsomes. Data obtained suggest that sodium selenite at physiological concentrations does not influence formation of active oxygen species by cytochrome P-450 and the rate of enzymatic LPO in rat liver microsomes.

The influence of "essential" phospholipids (EPL) on phase-I- and phase-II-reactions and on the glutathione status in the liver of aging rats.

"Essential" phospholipids (EPL; polyene-phosphatidylcholine) were administered orally to aging male rats in doses of 100 and 300 mg/kg b.wt. over 10 weeks. One and 7 days after the last treatment cytochrome P-450 concentration, epoxide hydrolase and glutathione-S-transferases were found to be unchanged, but ethylmorphine N-demethylation, ethoxycoumarin O-deethylation and UDP-glucuronosyltransferase activities were enhanced, as were the concentrations of both reduced and oxidized glutathione, the values being similar to those in young adult rats. These results are discussed in terms of an increase in endoplasmic reticulum membrane fluidity.

Experimental treatment of thioacetamide-induced liver cirrhosis by metenolone acetate. A morphological and biochemical study.

The influence of metenolone acetate (1 mg/kg b.m. orally) on intact and chronically thioacetamide-injured rat liver (experimental liver cirrhosis) was investigated over 14 d. Histological examination revealed nodular transformation of liver structure according to cirrhosis like lesions with hepatocellular and cholangiocellular proliferations. These structural alterations were more serious in the group treated with metenolone compared with the group without metenolone. Metanolone administration to animals with thioacetamide-induced experimental liver cirrhosis led to an increase in liver injury. This treatment seems to promote hepatic preneoplastic lesions induced by thioacetamide reflected by histology and induction of gamma-glutamyltranspeptidase and 7-ethoxycoumarin O-deethylase in injured livers. Metenolone did not interfere directly with the processes of connective tissue synthesis and degradation after thioacetamide pretreatment. Only little changes of the investigated biochemical parameters were seen after metenolone administration to animals with intact liver function: increases in serum cholinesterase and tissue N-acetyl-beta-D-glucosaminidase activity; decreases in N-acetyl-beta-D-glucosaminidase in serum, liver hydroxyproline content and hepatic gamma-glutamyltranspeptidase activity. The observed changes reflect hepatic adaption processes under the influence of metenolone. The results of this study indicate that the risk of anabolic steroids in adjuvant therapy of liver cirrhosis cannot be calculated at present.

[Effect of levonorgestrel and ethinyl estradiol and their combination on biotransformation reactions]. / Zum Einfluss von Levonorgestrel und Ethinylestradiol sowie deren Kombination auf die Aktivität von Biotransformationsreaktionen.

Caffeine is mainly metabolized by 3-methylcholanthreneinducible cytochrome P-450, whereas metamizol (Analgin) is probably mainly metabolized by the phenobarbital inducible cytochrome P-450 family. Therefore the elimination of caffeine from serum and the elimination of the main metabolites of metamizol in urine reflect the activity of these two cytochrome P-450 families. Sex hormones can influence the activity of cytochrome P-450. Intake of levonorgestrel (0.125 mg) daily for 14 days reduced the metabolism of caffeine slightly, but the elimination of metamizol-metabolites is not influenced. Longterm administration of levonorgestrel (0.250 mg daily) for three months did not change the metabolisms of both model substances tested. In contrast, ethynylestradiol (0.050 mg) alone and also the combination with levonorgestrel markedly retarded the elimination rate of caffeine and metamizol-metabolites. This fact should be taken into consideration in drug therapy.

Prepartal lactose concentration in the mammary glands of Uje: WIST rats as a simple indicator of approaching parturition.

Immediately after delivery, lactose was reliably detectable in rat mammary glands (mean concentration 6.49 +/- 0.57 mg/g tissue). The concentrations were not influenced by prepartal biopsy of contralateral mammary tissue. In the morning of the 21st day of gestation (= expected day of labor), lactose was evident in the mammary glands of dams delivering at that day (mean concentration 2.39 +/- 0.17 mg/g tissue). In the tissue of dams delivering on day 22 of gestation, lactose was undetectable. A correlation between prepartal lactose concentration of mammary gland and time remaining up to beginning of delivery (r = -0.96) qualifies this parameter as a rough indicator of term of parturition.

[The effect of intrahepatic cholestasis in pregnancy on various forms of cytochrome P-450-dependent biotransformation reactions]. / Der Einfluss der intrahepatischen Schwangerschaftscholestase auf verschiedene Cytochrom P-450-abhängige Biotransformations-reaktionen.

The elimination of caffeine from plasma and the excretion of the main metabolites of metamizol (noramidopyrinemethanesulphonate sodium) into the urine were determined in healthy pregnant women (weeks 30-38 of pregnancy) and in patients with intrahepatic cholestasis in pregnancy (weeks 28-39 of pregnancy). From the elimination velocity of these model substances conclusions concerning the activity of 3-methylcholanthrene (caffeine elimination) and phenobarbital inducible isoenzymes (metamizol elimination) of cytochrome P-450 are drawn. Patients with intrahepatic cholestasis in pregnancy (t1/2 = 15.8 +/- 1.8 h) eliminate caffeine more slowly than healthy pregnant women (t1/2 = 11.0 +/- 0.8 h) at this stage of pregnancy. The excretion of the metabolites of metamizol is only in tendency diminished in patients with intrahepatic cholestasis. The influence of the intrahepatic cholestasis on the cytochrome P-450 isoenzymes investigated differs in degree.

[Effect of various liver diseases on the activity of 2 subtypes of cytochrome P-450]. / Zum Einfluss von verschiedenen Lebererkrankungen auf die Aktivität zweier Subtypen des Cytochrom P-450.

The elimination of caffeine from the plasma and the elimination of metamizol-metabolites in urine were determined in 37 patients with different liver diseases. In severe liver diseases the demethylation of caffeine as well as the metabolism of metamizol is significantly reduced. The extent of reduced elimination capacity depends on the severity of the disease rather than on the type of disease. In patients with liver cirrhosis the determination of synthesis capacity and of humoral activity (s. tab. I) is suitable to evaluate the capacity of the cytochrome P-450 system. In noncirrhotic diseases only the activity of liver disease (tab. I.) determines the extent of reduced biotransformation capacity. Beside biotransformation-phase I, the acetylation--phase II biotransformation--also appears to be reduced.

[Elimination of caffeine and metamizole in the menstrual cycle of the fertile female]. / Untersuchungen zur Elimination von Coffein und Metamizol im Menstruationszyklus der fertilen Frau.

The elimination of caffeine from serum and that of the main metabolites of metamizol in serum were investigated in 9 healthy women on days 1, 8, 14 and 21 of the menstrual cycle. In the luteal phase, when the progesterone level is highest and the estradiol concentration is high as well, the elimination of caffeine is about 25% longer than in the follicular phase. In contrast to caffeine, the metabolism of metamizol is slightly accelerated if the endogenous hormone level is high. The present results suggest that endogenous hormones have different effects on biotransformation activities. These results are without practical consequences yet.

[Elimination of caffeine and metamizol in in vivo characterization of cytochrome P-450 dependent biotransformation reactions in aged humans]. / Die Elimination von Coffein und Metamizol zur in-vivo-Charakterisierung Cytochrom P-450-abhängiger Biotransformationsreaktionen beim alten Menschen.

Elimination of caffeine from plasma and excretion of main metabolites of metamizol (noramidopyrine methanesulphonate sodium) in urine were determined in young healthy (age 18-27 years) and in old aged volunteers (older than 65 years). From the elimination velocity of these model substances conclusions concerning the activity of 3-methylcholanthrene inducible (caffeine elimination) and of phenobarbital inducible (metamizol elimination) isoenzymes of cytochrome P-450 are drawn. Whereas in old age caffeine metabolism is unchanged, there is a strong delay in renal excretion of main metabolites of metamizol in old volunteers. It is concluded that different hepatic cytochrome P-450 isoenzymes are differentially influenced with increasing age in men.

[The influence of chronic renal insufficiency on the demethylating activities of various cytochrome P-450 subspecies in humans]. / Einfluss der chronischen Niereninsuffizienz auf durch verschiedene Cytochrom P-450-Subspezies katalysierte Demethylierungsaktivitäten beim Menschen.

Caffeine is mainly metabolized by 3-methylcholanthrene-inducible cytochrome P-450 (P-450MC) and metamizol (noramidopyrine methanesulfonate sodium) is mainly metabolized by phenobarbital-inducible cytochrome P-450 (P-450PB). That's why the half life of caffeine and the elimination of the main metabolites of metamizol were used as parameters in vivo characterizing both groups of the cytochrome P-450-complex. The influence of chronic renal insufficiency was investigated (8 patients in the stage of compensated retention, creatinine in serum 380-1280 mumol X l-1, and 6 hemodialyzed patients, here only metamizol elimination was established). Both the caffeine and the metamizol eliminations of patients with chronic renal insufficiency are not different from those of healthy volunteers. We concluded that the demethylation activity of the cytochrome P-450-complex is not distinctly influenced by chronic renal insufficiency.

[Determination of caffeine and metamizole elimination in pregnancy and after delivery as an in vivo method for characterization of various cytochrome p-450 dependent biotransformation reactions]. / Bestimmung der Elimination von Koffein und Metamizol in der Schwangerschaft und im Wochenbett als in vivo-Methode zur Charakterisierung verschiedener Zytochrom P-450-abhängiger Biotransformationsreaktionen.

The elimination of caffeine from plasma and the elimination of the main metabolites of metamizol in urine were measured in 20 pregnant women, 19 puerperants, and 10 young healthy female non-pregnant volunteers. It was found a significant prolongation of caffeine elimination in pregnancy (t 1/2 = 9.4 +/- 0.6 h) with a correlation between duration of pregnancy and elimination half-life of caffeine (v = 0.72). The amount of the main metabolites of metamizol eliminated 0-9 h after application of the drug decreased from 82.6 +/- 8.2 mg in nonpregnant volunteers to 45.6 +/- 5.7 mg in pregnant women. Whereas caffeine elimination is restored within the first week after delivery, the rate of metamizol elimination does not reach the value of the non-pregnant volunteers in this period.

[Determination of caffeine and metamizole elimination in men and women with and without hormonal contraceptives as an in vivo method for characterization of various cytochrome P-450 subspecies]. / Die Bestimmung der Coffein- und Metamizolelimination bei Männern und Frauen ohne sowie unter hormonalen Kontrazeptiva als in-vivo-Methode zur Charakterisierung verschiedener Cytochrom P-450 Subspezies.

Caffeine is mainly metabolized by 3-methylcholanthrene-inducible cytochrome P-450 (P-450MC) and noramidopyrine-methanesulfonate sodium (metamizol, Analgin) is mainly metabolized by phenobarbital-inducible cytochrome P-450 (P-450PB). We investigated the elimination of caffeine by the use of plasma concentration curves (HPLC) and the elimination of metamizol by spectrophotometric determination of the metabolites in urine in 10 healthy young males, in 10 healthy young females using no OL-steroids and in 10 healthy young females using OC-steroids. No influence of sex on the microsomal drug metabolism activity of these two drugs has been observed. There was a significantly decreased microsomal drug metabolism of both drugs in females under hormonal contraception. We conclude that OC-steroids decrease the demethylation activity of both P-450MC and P-450PB.

[Renal excretion of long term sulfonamides under fluid administration and modification of the urinary pH value]. / Renale Ausscheidung von Langzeitsulfonamiden bei Flüssigkeitsbelastung und Anderung des pH-Wertes des Harns

The renal excretion of sulfaclomide, sulfamerazine and sulfamethoxypyridazine is delayed by increased fluid application in rats. The simultaneous administration of sulfonamides and ammonium chloride or sodium hydrogen carbonate causes, respectively, retardation and acceleration of renal sulfonamide excretion which is consistent with the change in urinary pH value. The retarded renal sulfonamide excretion with increasing diuresis is explained by the ensuing change in the urinary pH value. For clinical uses, a speedy renal excretion of long-time sulfonamides by increased diuresis can be expected only if alkalization of the urine is achieved at the same time.