Nonadditive effects of combined in vivo hepatic microsomal enzyme inducers in the Wistar rat

1983 ◽  
Vol 61 (9) ◽  
pp. 983-988 ◽  
Author(s):  
Larry S. Gontovnick ◽  
Geoffrey Sunahara ◽  
Gail D. Bellward
Keyword(s):  
Adult Female ◽  
Wistar Rat ◽  
Female Rats ◽  
Male Rats ◽  
Hepatic Microsomes ◽  
Trans Stilbene ◽  
Microsomal Enzyme Inducers ◽  
Nonadditive Effects ◽  
Cytochrome P 450

Compounds that are known to increase the hepatic microsomal cytochrome P-450 dependent monooxygenases were adminstered to adult female rats, alone or in combination, to determine whether their effects on certain substrate oxidations were additive. 3-Methyleholanthrene (3-MC) and pregnenolone-16α-carbonitrile (PCN), known to induce different forms of cytochrome P-450, when administered together increased benzo[a]pyrene oxidation to the same level as observed following 3-MC treatment alone. Phenobarbital (Pb) and PCN when administered concomitantly increased benzo[a]pyrene, aminopyrine, and ethylmorphine metabolism to the same extent as seen following PCN administration alone. Both compounds are known to induce different forms of cytochrome P-450. Nonadditive effects were also observed with Pb and spironolactone, as well as with Pb and trans-stilbene oxide. Treatment of adult male rats with either PCN or 3-MC resulted in significantly smaller increases in benzo[a]pyrene oxidation than observed in adult female rats. These results suggest that oxidative metabolism in hepatic microsomes is not the sum of activities of a number of cytochrome P-450s, but may represent the activity of a single predominant hemeprotein. In addition, it appears that the oxidation of substrate by a particular cytochrome P-450, in intact microsomes, is greatly influenced by the presence of another form.

Inactivation of rat liver microsomal steroid hydroxylations by 4-alkyl analogues of 3,5-diethoxycarbonyl-1,4-dihydro-2,4,6-trimethylpyridine: evidence for selectivity among steroid-inducible cytochrome P450IIIA forms

1990 ◽  
Vol 68 (12) ◽  
pp. 1533-1541 ◽  
Author(s):  
D. S. Riddick ◽  
I. McGilvray ◽  
G. S. Marks
Keyword(s):  
Rat Liver ◽  
Time Dependent ◽  
Female Rats ◽  
Male Rats ◽  
Prosthetic Group ◽  
Treated Male ◽  
Hepatic Microsomes ◽  
Dependent Inactivation ◽  
Heme Prosthetic Group ◽  
Cytochrome P 450

Various 4-alkyl analogues of 3,5-diethoxycarbonyl-1,4-dihydro-2,4,6-trimethylpyridine (DDC) cause mechanism-based inactivation of cytochrome P-450 (P-450) via destruction of the heme prosthetic group. This is an important component of these compounds' porphyrinogenic mechanism. In an attempt to map the P-450 isozyme selectivities of DDC analogues, we have examined the effects of these compounds on the regioselective and stereoselective hydroxylation of androstenedione (AD) and progesterone (PG) in rat liver microsomal systems. In microsomes from phenobarbital-treated male rats, DDC analogues did not cause time-dependent inactivation of AD 7α-hydroxylase, AD 16β-hydroxylase, and PG 21-hydroxylase, selective markers for P450IIA1/2, IIB1, and IIC6, respectively. In contrast, DDC analogues were effective inactivators of PG 2α-hydroxylase and steroid 6β-hydroxylases, selective markers for P450IIC11 and IIIA forms, respectively. We conclude that differences in porphyrinogenicity observed with various DDC analogues are not likely to be due to the selective destruction of different P-450 isozymes by different analogues, but rather to properties of the DDC analogues themselves. 4-Ethyl DDC was found to be capable of discriminating between P450IIIA subfamily forms. In microsomes from untreated male rats, which express P450IIIA2 but not IIIA1, 4-ethyl DDC inactivated both AD and PG 6β-hydroxylases. However, in microsomes from dexamethasone-treated female rats, which express P450IIIA1 but not IIIA2, no inactivation of the steroid 6β-hydroxylases was observed. Thus, 4-ethyl DDC appears to be a potentially valuable tool for differentiating between P450IIIA forms.Key words: 3,5-diethoxycarbonyl-1,4-dihydro-2,4,6-trimethylpyridine, cytochrome P-450, mechanism-based inactivation, rat hepatic microsomes, steroid hydroxylations.

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)

Attenuated responses of muscle protein synthesis to fasting and insulin in adult female rats

1992 ◽  
Vol 262 (1) ◽  
pp. E1-E5 ◽  
Author(s):  
A. G. Baillie ◽  
P. J. Garlick
Keyword(s):  
Protein Synthesis ◽  
Adult Female ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Fiber Type ◽  
Female Rats ◽  
Adult Rats ◽  
Fractional Rate ◽  
The Individual

One-year-old adult female rats were fasted for 12 or 36 h followed by a 30-min infusion of insulin. The responses of the fractional rate of protein synthesis (Ks) in the individual muscles (measured in vivo) to fasting were small and mostly nonsignificant. After 12 h of fasting, only the epitrochlearis muscle (ET) showed a significant decrease in Ks, and, even after 36 h of fasting, a significant decrease in Ks was seen in only ET, extensor digitorum longus, and tensor fasciae latae (TFL). After the 36-h fast, infusion of insulin restored the fed Ks in all muscles except TFL. The fiber-type composition of the individual muscles appeared to influence the muscles' responsiveness to the fasting, since the highly glycolytic TFL was the most sensitive (particularly after 36 h of fasting), whereas the highly oxidative adductor longus and soleus muscles were unaffected by either fasting or insulin. In a second experiment, refeeding of fasted adult rats also had little effect on Ks, consistent with the low sensitivity to fasting shown by the first experiment. The parallel results in the two experiments confirmed that the low responsiveness to fasting and insulin infusion in these adult rats was not a result of failure to absorb in “fed” animals or insufficient levels of insulin during insulin infusions. In contrast, a third experiment showed that muscle protein synthesis in the gastrocnemius muscle from young adult (5-mo-old) female rats was significantly reduced after only 12 h of fasting.

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.

Effects of Ghrelin upon Gonadotropin-Releasing Hormone and Gonadotropin Secretion in Adult Female Rats: In vivo and in vitro Studies

2005 ◽  
Vol 82 (5-6) ◽  
pp. 245-255 ◽  
Author(s):  
Rafael Fernández-Fernández ◽  
Manuel Tena-Sempere ◽  
Víctor M. Navarro ◽  
María L. Barreiro ◽  
Juan M. Castellano ◽  
...  
Keyword(s):  
Adult Female ◽  
Gonadotropin Releasing Hormone ◽  
In Vitro Studies ◽  
Female Rats ◽  
Gonadotropin Secretion ◽  
Releasing Hormone

N-(3,5-dinitrophenyl)-5-methoxytryptamine, a novel melatonin antagonist: effects on sexual maturation of the male and female rat and on oestrous cycles of the female rat

1988 ◽  
Vol 116 (1) ◽  
pp. 43-53 ◽  
Author(s):  
M. Laudon ◽  
Z. Yaron ◽  
N. Zisapel
Keyword(s):  
Drinking Water ◽  
Adult Female ◽  
Sexual Maturation ◽  
Young Male ◽  
Female Rats ◽  
Male Rats ◽  
Female Rat ◽  
Simultaneous Administration ◽  
Serum Concentrations ◽  
The Brain

ABSTRACT N-(3,5-dinitrophenyl)-5-methoxytryptamine (ML-23) has recently been synthesized and shown to antagonize the inhibitory effect of melatonin on the release of dopamine in vitro from the hypothalamus of female rats. In the present study the ability of ML-23 to inhibit in vivo the following melatonin-mediated effects was investigated: (1) delayed sexual maturation of young male rats, (2) delayed sexual maturation of young female rats, (3) inhibition of ovulation in mature female rats and (4) re-establishment of oestrous cycles in adult female rats maintained in continuous light. The inhibitory effect of daily melatonin injections, given in the afternoon, on the growth of the prostate gland and seminal vesicles and on serum testosterone concentrations in young male rats was prevented by daily injections of ML-23. Daily injections of ML-23 alone did not affect sexual maturation of young rats. In young male rats treated through the drinking water with melatonin, the growth of the accessory sex organs, but not that of the testes, was delayed and serum concentrations of testosterone were lower than in untreated rats. Administration of ML-23 through the drinking water increased serum concentrations of testosterone but did not significantly affect the weights of the accessory sex organs. Simultaneous administration of ML-23 and melatonin through the drinking water prevented completely, in a dose-dependent manner, the melatonin-mediated decrease in epididymal weights and in serum concentrations of testosterone and partially inhibited the delayed growth of the prostate glands and seminal vesicles. In young female rats treated with melatonin through the drinking water for 30 days, the growth of the ovaries was inhibited and serum concentrations of oestradiol were lower than in untreated rats. The growth of the uterus was not significantly affected. Administration of ML-23 through the drinking water did not significantly affect uterine and ovarian weights or oestradiol concentrations. Simultaneous administration of melatonin and ML-23 through the drinking water prevented completely the melatonin-mediated decrease in ovarian weights and in serum oestradiol concentrations. Ovulation during presumptive oestrus was prevented in adult female rats treated through the drinking water for 7 days with melatonin. Administration of ML-23 alone did not significantly affect the average numbers of ova shed and corpora lutea present. Simultaneous administration of ML-23 and melatonin prevented completely the melatonin-mediated inhibition of ovulation; the average number of ova shed was the same as in controls. Suppression of reproductive cycles occurred in adult female rats after long-term exposure to continuous light. This suppression was prevented by daily injections of melatonin in the afternoon; the incidence of constant oestrus decreased by 80%. Simultaneous injection of ML-23 and melatonin into rats maintained under continuous illumination prevented the effect of melatonin, and all the animals remained in constant oestrus. Administration of ML-23 alone did not alter the incidence of constant oestrus. A tritium-labelled derivative of ML-23 was prepared and administered orally to male rats. Peak concentrations of ML-23 occurred in the blood within 30 min after feeding and disappeared subsequently with a half-life of about 42 min. Intraperitoneal injection of [3H]ML-23 resulted in the appearance of peak concentrations of the drug in the brain within 20 min. The effects of ML-23 on serotonin S1 and S2 receptors, dopamine D2 receptors and melatonin receptors in the brain of the male rat were investigated using [3H]serotonin, [3H]spiperone and 2-[125I]iodomelatonin respectively. The binding of [3H]serotonin to brain synaptosomes and of [3H]spiperone to synaptosomes prepared from the cortical and caudate regions of the cerebrum was unaffected by ML-23 (10 μmol/l), whereas the binding of 2-[125I]iodomelatonin to brain synaptosomes was entirely inhibited. The results demonstrate the potency of ML-23 in antagonizing melatonin-mediated effects in the male and female rat in vivo. The drug may be administered to the animals simply through the drinking water, for relatively long periods without apparent deleterious effects on survival and welfare. ML-23 is accessible to both central and peripheral sites and acts specifically on melatonin but not on serotonin or dopamine receptors in the brain. The availability of a melatonin antagonist offers new opportunities for exploring the physiological role of melatonin in the neuroendocrine system. J. Endocr. (1988) 116, 43–53

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