Mechanism-based inactivation of hepatic cytochrome P450 2C6 and P450 3A1 following in vivo administration of 3,5-diethoxycarbonyl-1,4-dihydro-2,6-dimethyl-4-ethylpyridine to rats: differences from previously observed in vitro results

1994 ◽  
Vol 72 (4) ◽  
pp. 397-401 ◽  
Author(s):  
S. M. Kimmett ◽  
J. P. McNamee ◽  
G. S. Marks
Keyword(s):  
Cytochrome P450 ◽  
Competitive Inhibition ◽  
Female Rats ◽  
Male Rats ◽  
Hepatic Microsomes ◽  
In Vitro Effects ◽  
P450 Isozymes ◽  
In Vivo Administration

Using progesterone 21-hydroxylase as a selective substrate for P450 2C6 in phenobarbital-treated male rats, and androstenedione and progesterone 6β-hydroxylases as well as erythromycin N-demethylase as selective markers for P450 3A1 in dexamethasone-treated female rats, we have shown that these P450 isozymes undergo mechanism-based inactivation after in vivo administration of 3,5-diethoxycarbonyl-1,4-dihydro-2,6-dimethyl-4-ethylpyridine (4-ethyl DDC). These results differ from our previous studies where no inactivation was observed after in vitro administration of 4-ethyl DDC to rat hepatic microsomes. We show that the differences between the in vivo and in vitro effects of 3,5-diethoxycarbonyl-1,4-dihydro-2,4,6-trimethylpyridine (DDC) analogues are due to the presence of residual 4-ethyl DDC in the in vitro experiments causing time-independent competitive inhibition and obscuring observation of mechanism-based inactivation.Key words: 3,5-diethoxycarbonyl-1,4-dihydro-2,6-dimethyl-4-ethylpyridine, cytochrome P450, steroid hydroxylation, rat hepatic microsomes.

Effects of in vivo gonadal hormone environment on in vitro hGRF-40-stimulated GH release

1985 ◽  
Vol 249 (3) ◽  
pp. E276-E280 ◽  
Author(s):  
W. S. Evans ◽  
R. J. Krieg ◽  
E. R. Limber ◽  
D. L. Kaiser ◽  
M. O. Thorner
Keyword(s):  
Female Rats ◽  
Male Rats ◽  
Gonadal Hormone ◽  
Base Line ◽  
Pituitary Cells ◽  
Intact Male ◽  
Castrate Male ◽  
Basal Release

The effects of gender and the gonadal hormone environment on basal and stimulated growth hormone (GH) release by dispersed and continuously perifused rat anterior pituitary cells were examined. Cells from intact male and diestrus day 2 female rats and from castrate male rats either untreated or treated with testosterone (T) or 17 beta-estradiol (E2) were used. Basal GH release (ng/min per 10(7) cells; mean +/- SE) by cells from diestrus day 2 female rats was less than by cells from castrate rats treated with T (4.3 +/- 0.6 vs. 11.4 +/- 2.7, respectively; P less than 0.025). No other differences in basal release were detected. Concentration-response relationships were documented between human GH-releasing factor 40 (hGRF-40; 0.03-100 nM given as 2.5-min pulses every 27.5 min) and GH release. Mean (+/- SE) overall GH release (ng/min per 10(7) cells) above base line was greater by cells from intact male rats (496 +/- 92) than by cells from castrate (203 +/- 37.3; P less than 0.0001), castrate and T-treated (348 +/- 52.8; P = 0.008), or castrate and E2-treated (58.1 +/- 6.8; P less than 0.001) male rats or by diestrus day 2 rats (68.6 +/- 9.5; P = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Phenobarbital influence on neuromuscular block produced by rocuronium in rats

2008 ◽  
Vol 23 (4) ◽  
pp. 343-347 ◽  
Author(s):  
Angélica de Fátima de Assunção Braga ◽  
Caroline Coutinho de Barcelos ◽  
Franklin Sarmento da Silva Braga ◽  
Samanta Cristina Antoniassi Fernandes ◽  
Yoko Oshima Franco ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Neuromuscular Blockade ◽  
Neuromuscular Block ◽  
Cytochrome B5 ◽  
Muscle Response ◽  
In Vivo Experiments ◽  
Hepatic Microsomes ◽  
Enzymatic Induction

PURPOSE: To evaluate in vitro and in vivo neuromuscular blockade produced by rocuronium in rats treated with Phenobarbital and to determine cytochrome P450 and cytochrome b5 concentrations in hepatic microsomes. METHODS: Thirty rats were included in the study and distributed into 6 groups of 5 animals each. Rats were treated for seven days with phenobarbital (20 mg/kg) and the following parameters were evaluated: 1) the amplitude of muscle response in the preparation of rats exposed to phenobarbital; 2) rocuronium effect on rat preparation exposed or not to phenobarbital; 3) concentrations of cytochrome P450 and cytochrome b5 in hepatic microsomes isolated from rats exposed or not to phenobarbital. The concentration and dose of rocuronium used in vitro and in vivo experiments were 4 µg/mL and 0,6 mg/kg, respectively. RESULTS: Phenobarbital in vitro and in vivo did not alter the amplitude of muscle response. The neuromuscular blockade in vitro produced by rocuronium was significantly different (p=0.019) between exposed (20%) and not exposed (60%) rats; the blockade in vivo was significantly greater (p=0.0081) in treated rats (93.4%). The enzymatic concentrations were significantly greater in rats exposed to phenobarbital. CONCLUSIONS: Phenobarbital alone did not compromise neuromuscular transmission. It produced enzymatic induction, and neuromuscular blockade in vivo produced by rocuronium was potentiated by phenobarbital.

Effect of dexamethasone treatment on the biotransformation of glyceryl trinitrate: cytochrome P450 3A1 mediated activation of rat aortic guanylyl cyclase by glyceryl trinitrate

1994 ◽  
Vol 72 (12) ◽  
pp. 1513-1520 ◽  
Author(s):  
Bernard J. McDonald ◽  
Greg J. Monkewich ◽  
Patrick G. Long ◽  
Diane J. Anderson ◽  
Paul E. Thomas ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Glyceryl Trinitrate ◽  
Guanylyl Cyclase ◽  
Female Rats ◽  
Male Rats ◽  
Male And Female ◽  
Treated Male ◽  
Cyclase Activation ◽  
Male And Female Rats ◽  
Hepatic Microsomes

It is generally accepted that organic nitrates act via vascular biotransformation to an activator of guanylyl cyclase (presumably NO), resulting in increased cyclic GMP accumulation and vascular smooth muscle relaxation. Previously, we have shown that cytochrome P450 can mediate the biotransformation of glyceryl trinitrate (GTN) and that at least a portion of this biotransformation results in the formation of an activator of guanylyl cyclase. To assess the role of the cytochrome P450 3A subfamily in this phenomenon, we treated male and female rats with dexamethasone (DEX) (150 mg/kg, i.p., daily for 3 days). Under anerobic conditions, hepatic microsomal biotransformation of GTN was increased three-fold in DEX-treated male rats compared with all other treatment groups. Incubation of aortic 100 000 × g supernatant fraction from untreated rats (as a source of guanylyl cyclase) with GTN and hepatic microsomes from all groups resulted in concentration-dependent increases in guanylyl cyclase activation. Microsomes from DEX-treated male and female rats demonstrated a significantly greater activation of guanylyl cyclase compared with microsomes from untreated males and females. Furthermore, GTN-induced guanylyl cyclase activation mediated by microsomes from DEX-treated male and female rats was markedly inhibited by a polyclonal antibody raised to rat CYP3A1. Since CYP3A2 is absent or very low in hepatic microsomes from DEX-treated adult female rats, this identifies CYP3A1 as an isoform capable of biotransforming GTN to an activator of guanylyl cyclase. Similarly, CYP2C11 was identified as an isoform capable of biotransforming GTN to an activator of guanylyl cyclase, since monoclonal antibody to CYP2C11 inhibited GTN-induced activation of guanylyl cyclase mediated by microsomes from control male rats. In both male and female rats, DEX treatment had no effect on GTN-induced relaxation of isolated aorta. However, biotransformation of GTN in intact aorta from DEX-treated male rats was decreased. This suggests that DEX treatment affects only the aortic biotransformation of GTN that is not involved in the formation of an activator of guanylyl cyclase.Key words: glyceryl trinitrate, dexamethasone, guanylyl cyclase, cytochrome P450, vasodilation, biotransformation.

Role of estrogens and age in flow-mediated outward remodeling of rat mesenteric resistance arteries

2014 ◽  
Vol 307 (4) ◽  
pp. H504-H514 ◽  
Author(s):  
K. Tarhouni ◽  
M. L. Freidja ◽  
A. L. Guihot ◽  
E. Vessieres ◽  
L. Grimaud ◽  
...  
Keyword(s):  
Blood Flow ◽  
Female Rats ◽  
Male Rats ◽  
Resistance Arteries ◽  
Cross Sectional ◽  
Male And Female ◽  
Male And Female Rats ◽  
Arterial Contractility

In resistance arteries, a chronic increase in blood flow induces hypertrophic outward remodeling. This flow-mediated remodeling (FMR) is absent in male rats aged 10 mo and more. As FMR depends on estrogens in 3-mo-old female rats, we hypothesized that it might be preserved in 12-mo-old female rats. Blood flow was increased in vivo in mesenteric resistance arteries after ligation of the side arteries in 3- and 12-mo-old male and female rats. After 2 wk, high-flow (HF) and normal-flow (NF) arteries were isolated for in vitro analysis. Arterial diameter and cross-sectional area increased in HF arteries compared with NF arteries in 3-mo-old male and female rats. In 12-mo-old rats, diameter increased only in female rats. Endothelial nitric oxide synthase expression and endothelium-mediated relaxation were higher in HF arteries than in NF arteries in all groups. ERK1/2 phosphorylation, NADPH oxidase subunit expression levels, and arterial contractility to KCl and to phenylephrine were greater in HF vessels than in NF vessels in 12-mo-old male rats only. Ovariectomy in 12-mo-old female rats induced a similar pattern with an increased contractility without diameter increase in HF arteries. Treatment of 12-mo-old male rats and ovariectomized female rats with hydralazine, the antioxidant tempol, or the angiotensin II type 1 receptor blocker candesartan restored HF remodeling and normalized arterial contractility in HF vessels. Thus, we found that FMR of resistance arteries remains efficient in 12-mo-old female rats compared with age-matched male rats. A balance between estrogens and vascular contractility might preserve FMR in mature female rats.

Inhibitory effects of H2-receptor antagonists on cytochrome P450 in male ICR mice

1995 ◽  
Vol 14 (8) ◽  
pp. 623-629 ◽  
Author(s):  
DH Kim ◽  
EJ Kim ◽  
SS Han ◽  
JK Roh ◽  
TC Jeong ◽  
...  
Keyword(s):  
Cytochrome P450 ◽  
Liver Microsomes ◽  
Receptor Antagonists ◽  
Sleeping Time ◽  
Icr Mice ◽  
In Vitro Effects ◽  
Hexobarbital Metabolism ◽  
Dose Dependent

1 The present study was undertaken to examine the effects of H2-receptor antagonists including newly developed mifentidine derivatives, IY-80843 and IY-80845, on cytochrome P450(P450) in vitro and in vivo. 2 Initially, 3-methylcholanthrene-, phenobarbital-, ethanol- and dexamethasone-induced liver microsomes were prepared from male ICR mice to study in vitro effects of above chemicals on ethoxyresorufin O- deethylase(EROD), pentoxyresorufin O-dealkylase(PROD), p-nitrophenol hydroxylase and erythromycin N-demethy lase(ERDM) activities, respectively. It was found that hist amine, cimetidine and famotidine were not inhibitory to four enzyme activities. Meanwhile, mifentidine slightly inhibited EROD and PROD activities and its derivatives IY-80843 and IY-80845 strongly inhibited PROD, EROD and ERDM activities. 3 Prolongation of hexobarbital-induced sleeping time was determined in male ICR mice to confirm in vitro inhibito ry effects of mifentidine and its derivatives in vivo. It was observed that cimetidine, mifentidine, IY-80843 and IY- 80845 caused dose-dependent increases in the sleeping time, indicating the inhibition of P450 responsible for hexobarbital metabolism. 4 It was concluded that mifentidine and its derivatives are P450 inhibitors and that our newly synthesized IY-80843 is most inhibitory. 5 The present results indicate that mifentidine and its derivatives not only antagonise the H 2-receptor but also inhibit P450 enzymes.

scholarly journals Effects of Cytochrome P450 Inhibitors on Itraconazole and Fluconazole Induced Cytotoxicity in Hepatocytes

2009 ◽  
Vol 2009 ◽  
pp. 1-7 ◽  
Author(s):  
Nhareet Somchit ◽  
Chong Sock Ngee ◽  
Azhar Yaakob ◽  
Zuraini Ahmad ◽  
Zainul Amiruddin Zakaria
Keyword(s):  
Cytochrome P450 ◽  
Liver Perfusion ◽  
Antifungal Drugs ◽  
Female Rats ◽  
Atp Levels ◽  
P450 Inhibitors ◽  
Hepatocyte Toxicity

Itraconazole and fluconazole have been reported to induce hepatotoxicity in patients. The present study was designed to investigate the role of cytochrome P450 inhibitors, SKF 525A, and curcumin pretreatment on the cytotoxicity of antifungal drugs fluconazole and itraconazole. For 3 consecutive days, female rats were administered daily SKF 525A or curcumin (5 and 25 mg/kg). Control rats received an equivalent amount of dosed vehicle. The animals were anaesthetized 24 hours after receiving the last dose for liver perfusion. Hepatocytes were then exposed to various concentrations of antifungal drugs. In vitro incubation of hepatocytes with itraconazole revealed significantly lower viability when compared to fluconazole as assessed by lactate dehydrogenase, aspartate aminotransferase and alanine aminotransferase activities. The cytotoxicity of itraconazole was enhanced when incubated with hepatocytes pretreated with SKF 525A. SKF 525A had no effects on the cytotoxicity of fluconazole. Curcumin failed to either increase or decrease the cytotoxicity of both antifungal drugs. ATP levels also showed significant decrease in both itraconazole and fluconazole incubated hepatocytes. However, SKF 525A pretreated hepatocytes had significantly lower ATP levels after itraconazole incubations. Collectively, these results confirm the involvement of cytochrome P450 in the cytoprotection in itraconazole induced hepatocyte toxicity. Differences of the effects of SKF 525A on the cytotoxicity induced by itraconazole and fluconazole may be due to the differences on the metabolism of each antifungal drug in vivo.

scholarly journals Changes in RFamide-Related Peptide-1 (RFRP-1)-Immunoreactivity During Postnatal Development and the Estrous Cycle

Endocrinology ◽  
2014 ◽  
Vol 155 (11) ◽  
pp. 4402-4410 ◽  
Author(s):  
Sara R. Jørgensen ◽  
Mille D. Andersen ◽  
Agnete Overgaard ◽  
Jens D. Mikkelsen
Keyword(s):  
Postnatal Development ◽  
Estrous Cycle ◽  
Third Ventricle ◽  
Female Rats ◽  
Male Rats ◽  
Relative Distribution ◽  
Gonadotropin Secretion ◽  
Related Peptide

Abstract GnRH is a key player in the hypothalamic control of gonadotropin secretion from the anterior pituitary gland. It has been shown that the mammalian counterpart of the avian gonadotropin inhibitory hormone named RFamide-related peptide (RFRP) is expressed in hypothalamic neurons that innervate and inhibit GnRH neurons. The RFRP precursor is processed into 2 mature peptides, RFRP-1 and RFRP-3. These are characterized by a conserved C-terminal motif RF-NH2 but display highly different N termini. Even though the 2 peptides are equally potent in vitro, little is known about their relative distribution and their distinct roles in vivo. In this study, we raised an antiserum selective for RFRP-1 and defined the distribution of RFRP-1-immunoreactive (ir) neurons in the rat brain. Next, we analyzed the level of RFRP-1-ir during postnatal development in males and females and investigated changes in RFRP-1-ir during the estrous cycle. RFRP-1-ir neurons were distributed along the third ventricle from the caudal part of the medial anterior hypothalamus throughout the medial tuberal hypothalamus and were localized in, but mostly in between, the dorsomedial hypothalamic, ventromedial hypothalamic, and arcuate nuclei. The number of RFRP-1-ir neurons and the density of cellular immunoreactivity were unchanged from juvenile to adulthood in male rats during the postnatal development. However, both parameters were significantly increased in female rats from peripuberty to adulthood, demonstrating prominent gender difference in the developmental control of RFRP-1 expression. The percentage of c-Fos-positive RFRP-1-ir neurons was significantly higher in diestrus as compared with proestrus and estrus. In conclusion, we found that adult females, as compared with males, have significantly more RFRP-1-ir per cell, and these cells are regulated during the estrous cycle.

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