Search results for "microsomes"
showing 10 items of 193 documents
Antioxidant activity of anti-inflammatory plant extracts
2002
The antioxidant properties of twenty medical herbs used in the traditional Mediterranean and Chinese medicine were studied. Extracts from Forsythia suspensa, Helichrysum italicum, Scrophularia auriculata, Inula viscosa, Coptis chinensis, Poria cocos and Scutellaria baicalensis had previously shown anti-inflammatory activity in different experimental models. Using free radical-generating systems H. italicum. I. viscosa and F. suspensa protected against enzymatic and non-enzymatic lipid peroxidation in model membranes and also showed scavenging property on the superoxide radical. All extracts were assayed at a concentration of 100 microg/ml. Most of the extracts were weak scavengers of the hy…
Induction of cytochrome P450 and/or detoxication enzymes by various extracts or rosemary: description of specific patterns
2001
The ability of rosemary to modulate cytochrome P450 (CYP) and detoxication enzymes in rat liver was evaluated by comparing the effects of dried leaves and leaf extracts with different chemical compositions: essential oil (EO) containing monoterpenes, a dichloromethane extract (DCME) containing phenolic diterpenes and a water-soluble extract (WSE) containing phenolic compounds such as rosmarinic acid and flavonoids. Chemical analyses were done in order to characterize the composition of extracts. Male Wistar rats received the leaves or extracts of rosemary in their diet at 0.5% (w/w) for 2 weeks. The effects of such treatments were evaluated for CYP (1A, 2B, 2E1), glutathione S-transferase (…
Interrelationship between demethylation of p-nitroanisole and conjugation of p-nitrophenol in rat liver
1973
The metabolism of p-nitroanisole (pNA) and p-nitrophenol (pNP) was studied in isolated rat livers perfused with a hemoglobin-free medium. The activity and viability of the surviving organ was tested by recording pH, “arterial” and “venous” oxygen tension as well as the disappearance of added pNP. pNA is converted to its primary metabolite pNP which, in turn, is excreted into the perfusion medium as conjugates. The coordination of pNA oxidation and the conjugation reactions of pNP were investigated. When 50 μM pNA is added as substrate 0.4±0.1 nmoles×ml−1×(g liver)−1 are excreted as pNP-glucuronide and 3.5±0.2 nmoles×ml−1×(g liver)−1 as the sulphate within 90 min. When pNP itself (50 μM) is …
Biosynthesis and transformation of 20α 21-dihydroxycholesterol by rat adrenal preparations
1979
Abstract The biosynthesis of [ 3 H]-20α, 21 dihydroxycholestderol from [ 3 H]-20α-hydroxycholesterol and its transformation to [ 3 H]-21-hydroxypregnenolone by rat adrenal preparations has been demonstrated. 20α-Hydroxycholesterol was transformed to 20α, 21-dihydroxycholesterol by microsomal preparations in the presence of NADPH and 20α-21-dihydroxycholesterol was metabolized to 21-hydroxypregnenolone by mitochondrial preparations in the presence of a NADPH-generating-system. Comparison of the Michaelis-Menten-Kinetics of the steps “20α, 21-dihydroxycholesterol → 21-hydroxycholesterol” and “20α-hydroxycholesterol → pregnenolone” revealed that both compounds behaved as analogue substrates of…
Non-competitive inhibition of clomipramineN-demethylation by fluvoxamine
1995
The selective serotonin reuptake inhibitor fluvoxamine interferes with the metabolism of tricyclic antidepressants. The present investigation was set out to characterize these interactions in vitro using rat liver microsomes and in vivo by analysing levels of clomipramine and metabolites in sera of depressed patients treated concomitantly with fluvoxamine and clomipramine. Clomipramine was N-demethylated and hydroxylated in vitro by microsomes to N-desmethyl-clomipramine, 8-hydroxyclomipramine, and 10-hydroxyclomipramine. Kinetic analyses revealed Km values of 6.2 microM for N-demethylation and 1.2 microM for 8-hydroxylation. Fluvoxamine was a non-competitive inhibitor for N-demethylation w…
Effect of low levels of dietary fish oil on fatty acid desaturation and tissue fatty acids in obese and lean rats
1995
The effect of very low levels of dietary long-chain n-3 fatty acids on delta 6 desaturation of linoleic acid (18:2n-6) and alpha-linolenic acid (18:3n-3), and on delta 5 desaturation of dihomo-gamma-linolenic acid (20:3n-6), in liver microsomes and its influence on tissue fatty acids were examined in obese and lean Zucker rats and in Wistar rats. Animals fed for 12 wk a balanced diet containing ca. 200 mg of long-chain polyunsaturated n-3 fatty acids per 100 g of diet were compared to those fed the same amount of alpha-linolenic acid. Low amounts of long-chain n-3 fatty acids greatly inhibited delta 6 desaturation of 18:2n-6 and delta 5 desaturation of 20:3n-6, while delta 6 desaturation of…
Endogenous nitric oxide is responsible for the early loss of P450 in cultured rat hepatocytes
1998
AbstractLoss of P450 during the early hours of monolayer formation is known to be the more serious limitation of primary cultured hepatocytes as an adequate model for the study of drug metabolism, toxicity and P450 induction. This study reports that endogenous nitric oxide (NO) formation is activated shortly after isolation by the classical collagenase-based liver perfusion methods. Both rapid P450 loss and aerobic mitochondrial energy metabolism impairment – with subsequent changes on glucose metabolism – are directly related to the high local generation of the radical at this stage. These effects can be reverted by the sole addition of NO biosynthesis inhibitors during liver perfusion and…
Differential effect of hypophysectomy and growth hormone treatment on hepatic glucuronosyltransferases in male rats: Evidence for an action at a pret…
1997
International audience; The influence of growth hormone (GH) on 4-nitrophenol, bilirubin, testosterone, androsterone and estrone glucuronidation activities was studied in fully activated male rat hepatic microsomes. Sham-operated and hypophysectomized animals were injected with two different dosages of GH, mimicking either the male or female GH secretion pattern. Half the animals received thyroxine and cortisol in concentrations chosen to compensate for the lack of thyroid hormones and glucocorticoids in hypophysectomized rats. GH induced a decrease in several glucuronidation activities: bilirubin glucuronidation in both sham-operated and cortisol/ thyroxine-treated hypophysectomized rats i…
Long-term expression of differentiated functions in hepatocytes cultured in three-dimensional collagen matrix.
1998
Hepatocytes entrapped in collagen gel and cultured in serum-free conditions survived longer than cells cultured on plastic (5 days vs. 3 weeks), showed fewer signs of early cell senescence (no increase in c-fos oncoprotein expression), and maintained the expression of differentiated hepatic metabolic functions over a longer period of time. Cells cultured in collagen gels retained their ability to respond to hormones. The insulin-stimulated glycogen synthesis rate remained fairly constant during 18 days in culture (between 5.4 +/- 0.37 and 9 +/- 2.7 nmol glucose/h/microg DNA). Collagen-cultured hepatocytes recovered glycogen stores to levels similar to those found in liver, or in hepatocytes…
Role of thyroid state on induction by ciprofibrate of laurate hydroxylase and peroxisomal enzymes in rat liver microsomes.
1993
The effects of hypothyroidism and hyperthyroidism upon liver microsomal omega-laurate hydroxylase activity (cytochrome P450 IV A1-dependent), peroxisome proliferation marker enzyme activities and acyl CoA oxidase (AOX) expression induced by ciprofibrate (2 mg/kg/day during 8 days) were studied in the male Wistar rat so as to clarify firstly the possible involvement of thyroid hormones in the modification of peroxisomal ciprofibrate-induced enzyme activities in relation to hepatic microsomal cytochrome P450 IV A1 induction, and secondly the possible direct effect of thyroid hormones on the gene expression of specific peroxisomal enzymes. No significant change was found in the ciprofibrate-in…