脂多糖和甲双吡丙酮诱发形成豚鼠运动性哮喘模型

目的建立一种接近临床特点的运动性哮喘动物模型。方法豚鼠２７只分４组。实验组（Ａ组）用脂多糖（１ｍｇ／ｋｇ）和甲双吡丙酮（５０ｍｇ／ｋｇ）腹腔注射，４天后测定气道阻力和动态肺顺应性基础值，８小时后进行运动试验并复测上述指标。对照组有３组（Ｂ、Ｃ、Ｄ组）；分别为腹腔注射脂多糖和甲双吡丙酮不运动组、腹腔注射生理盐水运动组和腹腔注射生理盐水不运动组。结果实验组豚鼠在运动后肺阻力增高、动态肺顺应性降低，而３个对照组上述指标变化均无统计学意义。结论脂多糖和甲双吡丙酮腹腔注射可诱发形成豚鼠运动性哮喘模型     

The influence of Depot-β 1−24-Tetracosactide and of metyrapone on the excretion of free urinary cortisol in infants

In this paper we studied the urinary output of free cortisol using two experimental conditions: the first consists of basal values, a metyrapone test and a 3-days-load with tetracosactide. The second was carried out with a single dose of tetracosactid also after basal values.After metyrapone free urinary cortisol rose slighly less than the Porter-Silberchromogens the mean of raising factors being different with a p<0,02>0,01. The increase of free urinary cortisol may be used in this condition as a parameter for judging the capacity of C-11-hydroxylating enzyme system in basal state.After tetracosactide we found in both conditions an increase of urinary free cortisol showing a lens-effect regarding the values of the Porter-Silber-chromogens.It is concluded that free urinary cortisol can be used as a very sensitive parameter for judging increased adrenal activity, at least on premise of unaltered degradation rate of cortisol.We used in this study the ^1–24 with depot-effect from N. V. Organon, Oss, Netherlands.This study was supported by a grant (Sto 45/8) from the Deutsche Forschungsgemeinschaft, Bad Godesberg, West-Germany.     

Partial reversal of stress-induced behavioral sensitization to amphetamine following metyrapone treatment

Several studies indicate that blockade of stress-induced corticosterone secretion prevents the development of stress-induced sensitization to the behavioral effects of stimulants. The present study examined whether chronic blockade of corticosterone synthesis with metyrapone could reverse stress-induced amphetamine sensitization in rats. Restraint stress in cylindrical chambers, 2 times 30 min/day for 5 days over an 8-day schedule, was used as the stressor. Following completion of the stress protocol, animals were cannulated with microdialysis guide cannulae over the nucleus accumbens, and then treated with either metyrapone (50 mg/kg, i.p.) or vehicle (1 ml/kg) for 7 days. On the seventh day, animals were implanted with microdialysis probes in the nucleus accumbens, and on the following day, all animals were tested for their locomotor, stereotypy, and nucleus accumbens dopamine and DOPAC release responses to an injection of saline followed 60 min later by d-amphetamine (1.5 mg/kg, i.p.). Neither stress or metyrapone treatment had an effect on the behavioral or dopamine release response to saline. However, amphetamine-stimulated locomotion and stereotypy were strongly enhanced, while amphetamine-stimulated dopamine release response was slightly enhanced (significant only by drug×time interaction), in stressed animals. Metyrapone treatment reduced the stress-induced increase in the locomotor, but not stereotypy, response to amphetamine. In contrast, the dopamine release response to amphetamine was enhanced in metyrapone-treated animals, in both stressed and non-stressed groups, while DOPAC levels were unaffected by treatment group. This augmentation was particularly evident in the stressed-metyrapone-treated animals. Furthermore, non-stressed animals showed an increased locomotor and stereotypy response to amphetamine after treatment with metyrapone. These findings indicate that metyrapone treatment can reverse, or inhibit the expression of, stress-induced sensitization to the behavioral effects of amphetamine. However, the ability of metyrapone treatment to enhance the behavioral (in non-stressed animals) and dopamine release (in non-stressed and stressed animals) responses to amphetamine indicate that chronic metyrapone treatment will produce stimulant sensitization when given alone.     

Metabolic activation of halothane and its covalent binding to liver endoplasmic proteins in vitro

Summary Metyrapone inhibits the N-demethylation of aminopyrine and ethylmorphine in rat liver microsomes non-competitively with concentrations in the micromolar range, and competitively in the range of 10^–4 M. In the case of non-competitive inhibition, enzyme and inhibitor are present in similar amounts (mutual depletion system). Under these conditions Lineweaver-Burk kinetics do not apply, since the portion of inhibitor bound to the enzyme cannot be neglected. Inhibition of microsomal N-demethylating activity by increasing amounts of metyrapone and application of equations required for a mutual depletion system enable us to determine the following kinetic parameters: (1) the concentration of catalytically active and metyrapone sensitive centers (E _t ) of cytochrome P-450, (2) their turnover number (TN), and (3) the true dissociation constant of the enzyme inhibitor complex, K _i .—With aminopyrine as substrate and microsomes from phenobarbital (PB) pretreated rats, 1 mg of protein contains 4.7 nmoles of E _t , i.e. about 2.2 catalytically active sites per molecule of cytochrome P-450; TN=3.4 min^–1, and K _i =2.2·10^–6 M.The corresponding values for ethylmorphine and control rats are: E _t =3.1 nmolles per mg of protein (4.4 sites per molecule), TN=1.94 min^–1; K _i =2.37·10^–6M. PB-pretreated rats: E _t =7.3 nmoles per mg of protein (3.5 sites per molecule) TN=2.0 min^–1; K _i =2.3·10^–6 M.Comparing the values obtained for PB-pretreated rats and controls reveals that K _i and TN remain constant but E _t rises 2.3 fold. This is regarded to mean that PB pretreatment influences ethylmorphine N-demethylation only quantitatively but not qualitatively. The experiments described here provide data which improve the characterization of cytochrome P-450. They are derived from the overall rate of N-demethylation reactions in microsomes, independently from conventional spectrophotometric methods.     

Alteration of the inhibitory effect of metyrapone by reduction to metyrapol during the metabolism of methacetin in vivo in mice

Summary Metyrapone is known as an inhibitor of the oxidative drug metabolism in vitro. We have used the exhalation analysis as a tool to study the influence of this inhibitor on the demethylation of¹⁴C-methacetin in vivo. In parallel we investigated the reductive metabolism of metyrapone in mice by measuring the concentrations of metyrapone and its reduced metabolite metyrapol with a HPLC-method.50 mg of metyrapone/kg b. wt. resulted in a 90% inhibition of¹⁴CO₂ exhalation when given 2 min before the exhalation analysis was started. The prolongation of the intervals between i.p. metyrapone and substrate administration leads to a diminution of the in vivo inhibition. We found that the hepatic metyrapone concentration falls rapidly and passes the detection limit at 120 min. Transiently metyrapol reaches a maximal concentration 15 min after the application of metyrapone. The rapid reduction of metyrapone was confirmed in vitro with fresh mouse liver homogenates.The administration of metyrapol itself in vivo causes a decrease in¹⁴CO₂ exhalation, too. The¹⁴CO₂ exhalation curves after metyrapol correspond to the curves after metyrapone, when sufficient time was allowed for its reduction to metyrapol. It can be concluded that not only metyrapone itself but also its reductive metabolite metyrapol is an effective, however weaker inhibitor.     

Competitive inhibition of the microsomal N-hydroxylation of 4-chloroaniline by metyrapone and gyclohexane

Summary Metyrapone and cyclohexane inhibit competitively the N-hydroxylation of 4-chloroaniline in the microsomal fraction of rabbit livers.This work has been supported by the Deutsche Forschungsgemeinschaft.     

Permissive influence of stress in the expression of a U-shaped relationship between serum corticosterone levels and spatial memory errors in rats

The relationship between glucocorticoids (GCs) and memory is complex, in that memory impairments can occur in response to manipulations that either increase or decrease GC levels. We investigated this issue by assessing the relationship between serum corticosterone (the primary rodent GC) and memory in rats trained in the radial arm water maze, a hippocampus-dependent spatial memory task. Each day, rats learned a new location of the hidden escape platform and then 30 min later their memory of the location of the platform was tested. Under control conditions, well-trained rats had excellent spatial memory and moderately elevated corticosterone levels (approximately 26 microg/dl versus a baseline of approximately 2 microg/dl). Their memory was impaired when corticosterone levels were either reduced by metyrapone (a corticosterone synthesis inhibitor) or increased by acute stress (predator exposure), forming an overall U-shaped relationship between corticosterone levels and memory. We then addressed whether there was a causal relationship between elevated corticosterone levels and impaired memory. If elevated corticosterone levels were a sufficient condition to impair memory, then exogenously administered corticosterone, alone, should have impaired performance. However, we found that spatial memory was not impaired in corticosterone-injected rats that were not exposed to the cat. This work demonstrates that an intermediate level of corticosterone correlated with optimal memory, and either a decrease or an increase in corticosterone levels, in conjunction with strong emotionality, impaired spatial memory. These findings indicate that fear-provoking conditions, which are known to engage the amygdala, interact with stress levels of corticosterone to influence hippocampal functioning.     

Combinations of oxazepam and metyrapone attenuate cocaine and methamphetamine cue reactivity

Background

We have previously reported that combining low doses of oxazepam and metyrapone (OX/MET) reduces intravenous cocaine self-administration without affecting stress-hormone levels. We hypothesized that the combination of OX/MET would also inhibit the reinstatement of cocaine or methamphetamine seeking induced by the presentation of a conditioned reinforcer and that stress hormone levels would not be influenced by this treatment.

Methods

Male rats were implanted with jugular catheters and trained to self-administer cocaine or methamphetamine during daily 2-h sessions. During training, cocaine or methamphetamine delivery was paired with the presentation of a tone and the illumination of a house light. Following stable self-administration, rats were placed into forced abstinence. During cue-reactivity testing, rats were placed back into the operant chambers and responding only resulted in the presentation of the conditioned reinforcer; no cocaine or methamphetamine was delivered. Blood was collected on the last day of self-administration and on the day of cue-reactivity testing (either 15-min or 2-h session) to assess plasma corticosterone.

Results

The response-contingent presentation of the conditioned reinforcer reliably maintained cocaine or methamphetamine seeking following vehicle pretreatment. Pretreatment with OX/MET resulted in a dose-related attenuation of both cocaine and methamphetamine seeking. Corticosterone levels were significantly different at the end of the 15-min session, but not following the 2-h session.

Conclusion

These data suggest that OX/MET may be useful in blocking the ability of environmental cues to stimulate both cocaine and methamphetamine seeking and that this effect is not entirely dependent on stress hormone levels.     

Comparison of insulin hypoglycemia and short metyrapone tests in patients with pituitary disease

Summary In a retrospective study on 59 patients (2 hypothalamic, 44 pituitary, 13 no confirmed disease) 69 pairs of insulin hypoglycemia tests (IHT) and short metyrapone tests (SMT) were evaluated. Cortisol and 11-desoxy-cortisol rsp. were compared as the endpoints. In 6 cases, the IHT was a technical failure because of insufficient hypoglycemia. In 25% of 63 pairs of tests, both tests were normal, (Group I), in 30% both abnormal (Gr. II). In 21%, IHT was normal, SMT abnormal (Gr. III) and in 24% IHT was abnormal and SMT normal (Gr. IV). The 2 patients with hypothalamic disease were in Group IV with completely normal SMT and severely pathological IHT. Other discrepancies could not be attributed to special pituitary disorders. In 9 patients of Group III and in 8 patients of Group IV (n=17), the IHT alone was repeated 6–48 months after the original pair of tests which had been performed in most cases early after pituitary surgery. In 12 cases, the repeat IHT followed the trend of the SMT of the original test pair. In 5 cases, the IHT was unchanged. 14 of 19 patients of Group II, but only 5 of 28 patients of Group III and IV required permanent substitution with hydrocortisone. Conclusions. The SMT may be normal in patients wilth clearcut hypothalamic dysfunction of the CRF-ACTH axis. In pituitary disease, IHT and SMT seem to be equivalent tests of dysfunction. After pituitary surgery, the SMT may be a better prognostic test of ACTH recovery than the IHT. Permanent substitution therapy with hydrocortisone is usually required when both tests are abnormal, but rarely necessary if only one of the tests is abnormal.Abbreviations IHT Insulin hypoglycemia test - SMT Short metyrapone test Presented in part to the 90th Congress of the Deutsche Gesellschaft für Innere Medizin, Wiesbaden, 29.4.–3.5.1984