Immunological detection of CYP2E1 in fresh rat lymphocytes and its pretranslational induction by fasting.

The level of ethanol-inducible cytochrome P450 2E1 (CYP2E1) in fresh lymphocytes compared with cultured cells and its induction mechanism by fasting were studied. CYP2E1 in the homogenate and S-9 fraction of fresh lymphocytes was elevated about 5-fold by fasting, comparable to the induction observed in cultured lymphocytes. This induction was accompanied by increased level of CYP2E1 mRNA, confirmed by nested RT-PCRs, Southern blot, and DNA sequence analysis. Our data thus demonstrated that CYP2E1 in fresh lymphocytes is pretranslationally induced by fasting, in parallel to the hepatic enzyme, and that measurement of CYP2E1 in the lymphocyte homogenate can be useful to estimate the hepatic CYP2E1 level in a relatively noninvasive manner.

Cardiovascular effects of tropacocaine in conscious and anesthetized rabbits: lack of evidence for neuro-cardiac interactions and acute neurotoxicity.

The cardiovascular effects of tropacocaine, a structural analog of cocaine, were investigated in both conscious and anesthetized New Zealand white rabbits to determine if such effects were mediated through the CNS as had been demonstrated with cocaine, i.e., did a neuro-cardiac pathway exist? To facilitate the requisite cardiovascular measurements in both urethane- and pentobarbital-anesthetized animals, the right femoral artery and vein were cannulated for the measurement of arterial blood pressure and subsequent delivery of drugs, respectively. In addition, urethane-anesthetized animals had a branch of the left renal nerve isolated and multiunit renal nerve activity was monitored to obtain measures of sympathetic nerve activity originating from the CNS. Animals utilized in conscious experiments were surgically prepared 3 days prior to drug administration by placing canulae in the femoral artery and vein that were tunneled subcutaneously to the back between the scapulae. ECG and respiratory activity were also monitored in each animal. Doses of 0.3, 1, 3, and 10 mg/kg of tropacocaine were administered in both an ascending and descending fashion at 15 min intervals to 5 animals in each group, i.e., conscious, urethane-, and pentobarbital-anesthetized. In urethane-anesthetized animals a comparison was made between sympathetic renal nerve activity, systolic and diastolic blood pressure, respiratory rate, and heart rate. No pressor effects were observed and the changes in renal nerve activity could not be assigned as the cause of the observed depressor effects at the higher doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Vascular reactivity in alcoholic rat aortas: in vitro interactions between catecholamines and alcohol.

To understand the nature of vascular problems of hypertensive and alcoholic subjects, an in vitro interaction between catecholamine and alcohol was investigated in male Sprague-Dawley rats. The descending aortas were isolated from either the control or alcohol treated rats. The aortic strips were cooled rapidly in ice-chilled Krebs-Henseleit (K-H) solution and the aorta was cut into a series of rings of approximately 1 mm width. The rings were fixed under 1 g of resting tension between a force-displacement transducer and anchoring electrodes at 37 degrees C. The rings were equilibrated for an hour with frequent changes of the K-H solution before testing. There was norepinephrine (NE) dose-dependent contraction of the rings, which showed the maximum tension with 1 microM NE. Acetylcholine or carbachol produced slow relaxation. Pretreatment of the rings with 10 microM prazocin prevent the contraction induced by 1 microM NE. Even in the presence of prazocin, 60 mM KCI was able to generate the maximum tension. NE-induced contraction was analyzed in the control K-H solution or in the presence of 1.5, 3.0 and 5.0% of ethanol. Ethanol (1.5%) slowed the rate of rise of the aortic tension without a remarkable compromise of the maximum tension. But, there was a significant reduction in contraction with 3% ethanol. A complete inhibition of contraction was noted with 5% ethanol. However, the effect of ethanol was fully reversible upon washings the aortic rings with K-H solution. Aortic rings prepared from the rats that were fed with alcohol for 30 days were not able to generate the maximum tension with 1 microM NE.(ABSTRACT TRUNCATED AT 250 WORDS)

Microdialysis of noradrenaline in rostral ventrolateral medulla after intravenous methionine enkephalin administration in anesthetized rats.

The objective of this research was to define the role of central and peripheral opioid receptors for the regulation of cardiovascular action. Cardiovascular effects of methionine-enkephalin (met-enkephalin) after intracisternal, intravenous or direct administration into the rostral ventrolateral medulla (C1 area) were compared in inactin-anesthetized Sprague-Dawley rats. A microdialysis probe was stereotaxically implanted in the C1 area to dialyze monoamines during intravenous administration of met-enkephalin. An intravenous injection of met-enkephalin decreased both arterial pressure and heart rate in a dose-dependent manner. There were no cardiovascular responses to intracisternal dosages of up to 10 micrograms/kg, but as little as 0.1 micrograms/kg met-enkephalin decreased arterial pressure and heart rate after a direct injection into the C1 area. Onset of the met-enkephalin effect was similar regardless of drug doses after intravenous administration; however, duration and magnitude of the peptide's action and time to peak effect were directly related to the dose. Intravenous infusion of 100 micrograms/kg/min met-enkephalin increased the extracellular concentration of noradrenaline in the C1 area. There was a differential blockade by naloxone of the hypotensive action of met-enkephalin after intravenous or C1 administration. This study suggests the importance of both central and peripheral sites(s) of met-enkephalin for its cardiovascular action. Additionally, the data suggest that the C1 area is a communication site between catecholamines and opioid peptides for cardiovascular regulation.

Cardiovascular effects of mycelium extract of Ganoderma lucidum: inhibition of sympathetic outflow as a mechanism of its hypotensive action.

In an effort to understand the mechanism of cardiovascular actions of Ganoderma lucidum which was cultivated in Korea, the mycelium was isolated for a large-scale culture. Water extract of the mycelia was evaluated for its cardiovascular activity in anesthetized rabbits and rats. The left femoral artery and vein were cannulated for the measurement of arterial pressure and subsequent delivery of drugs. The left kidney was exposed retroperitoneally and a branch of the renal nerve was used to integrate renal efferent or afferent nerve activities. The extract decreased systolic and diastolic blood pressure, which was accompanied by an inhibition of renal efferent sympathetic nerve activity. The extract did not decrease heart rate in these animals, although there was clear hypotension in the extract dose dependent manner. This suggests that the hypotension induced by the treatment of the extract was secondary to the primary effect of the extract in the central nerve system, which suppressed the sympathetic outflow. Therefore we concluded that the mechanism of hypotensive action of Ganoderma lucidum was due to its central inhibition of sympathetic nerve activity.

Acute cardiovascular toxic effects of copper in anesthetized rabbits.

Copper deficiency is linked to many types of cardiovascular diseases. Copper toxicity may not be common, but it produces cardiac problems and even lethality. However, little is known about the precise mechanism of cardiotoxic action of copper in mammals. In an effort to characterize the cardiovascular effects and potential toxic action of copper, white New Zealand rabbits were instrumented for the measurement of cardiovascular parameters under urethane anesthesia. Left ventricular pressure and its dP/dt as well as the sympathetic efferent renal nerve activity were also monitored continuously before, during and after the injection of various doses of copper. Low doses of copper (3 mg/kg or less) increased blood pressure with a slight reduction in heart rate. There was also a transient increase in cardiac contractile force as shown by an increase of dP/dt with a reduction in sympathetic renal efferent nerve activity. However, high doses of copper (10 mg/kg or higher) decreased these cardiac parameters, which led to a state of shock, 90 seconds after the copper treatment. There was a compensatory increase in respiration rate and renal nerve activity during the shock. Thus, the data suggest that copper initially activates peripheral organs such as the heart and subsequently produces a distinct inhibitory action on sympathetic outflow, which is related to the toxic action of this metal.

Toxic effects of cocaine to the cardiovascular system in conscious and anesthetized rats and rabbits: evidence for a direct effect on the myocardium.

The cardiovascular toxicity of cocaine is complex because it has local anesthetic properties, central nervous system stimulatory effects, as well as cardiac effects. Recreational use of this drug has increased recently, but the precise mechanism of sudden cardiac death induced by cocaine is not known. The primary objective of this work was to test for a direct cardiovascular toxicity of cocaine. Rats and rabbits were anesthetized, and the femoral vein and artery were cannulated for drug infusion and blood pressure monitoring. Different doses of cocaine (0.3, 1, 3, 10 mg/kg) were infused. For conscious animal experiments, the animals were allowed to recover from the anesthesia and then were subjected to cocaine. Low doses of cocaine (0.3 and 1 mg/kg) increased systolic as well as diastolic pressure in conscious rats and rabbits. In anesthetized rats and rabbits, the same dose of cocaine increased blood pressure with a decrease in heart rate. With the high doses of cocaine (3 and 10 mg/kg), all cardiac parameters were reduced in both rats and rabbits. In isolated rabbit hearts, cocaine decreased all cardiac parameters. Based on the fact that high doses of cocaine severely depressed all cardiac parameters and its effect on the isolated heart, cocaine-induced sudden cardiac death appears to be due to a primary effect on the myocardium.

Hemodynamic and electrophysiological effects of mercury in intact anesthetized rabbits and in isolated perfused hearts.

Using intact anesthetized rabbits and isolated perfused hearts, the hemodynamic and electrophysiological effects of mercury (Hg) were examined in order to assess the role of cardiovascular dysfunction in Hg intoxication. The most consistent and prominent cardiovascular effect was a significant reduction in blood pressure. This cardiodepressive action was probably brought about by the primary action of Hg on the heart rather than by altered sympathetic activity, as evidenced by normal renal nerve activity at times when the hemodynamic actions of Hg were clearly manifest. Although the principal target organ for the toxic actions of inorganic Hg is the kidney, chronic exposure to both inorganic and organic Hg frequently results in signs and symptoms of CNS dysfunction. The profound hemodynamic effects of Hg that we have observed emphasize the potential importance of Hg cardiotoxicity and indicate the need to differentiate between the primary and the secondary effects of Hg intoxication on CNS tissues for evaluation of the toxic effects of Hg compounds.

Vascular responses to vasoactive agents in dietary alcohol-treated rats.

1. Young male Sprague-Dawley rats were fed on either solid regular rat chow, control liquid diet or liquid diet containing alcohol for 26 weeks. 2. Phenylephrine (0.5, 1, 2 or 4 micrograms/kg) was injected to monitor the reflexogenic bradycardia and nitroprusside (2, 4, 8 or 16 micrograms/kg) was also used to establish the relationship between drug-induced hypotension and baroreceptor-mediated tachycardia. 3. Multiunit renal nerve activity was determined under pentobarbitone anaesthesia as an index of sympathetic nerve activity during the treatment with phenylephrine or nitroprusside. 4. Alcohol-fed rats showed greater nerve responses to phenylephrine without corresponding decrease in heart rate, which suggests alcohol directly affects arterial wall compliance. This study does not support the contention that dietary alcohol increases blood pressure and it impairs significantly the baroreceptor function.

Are opioid receptors involved in the bradycardiac and hypotensive action of clonidine?

Experimental evidence that supports or rejects an involvement of opioid receptors in the cardiovascular effects of clonidine was sought. In anesthetized rabbits, clonidine decreased blood pressure and heart rate. These effects were related to the clonidine dose. High doses of clonidine produced a biphasic response in blood pressure without resulting in a significant baroreflex. However, it was not difficult to produce hypotensive action of clonidine without the biphasic action using low doses of clonidine. A pretreatment of the animals with naloxone (1 mg/1 kg) prevented the hypotensive action of clonidine at low dose. This antagonistic action of naloxone against clonidine was also evident in other cardiac parameters such as heart rate and efferent sympathetic renal nerve activity. The antagonistic action was not demonstrably significant with the high doses of clonidine. The present study in normotensive anesthetized rabbits suggests that specific central interactions between opioid and adrenergic receptors can be demonstrated under defined conditions, although such interactions were reported in pathophysiologic conditions such as essential hypertension.

Effects of [Met5]enkephalin on regional blood flow and vascular resistance in rabbits.

Methionine enkephalin [( Met5]enkephalin) has different cardiovascular effects, depending on species and routes of peptide administration. In anesthetized animals [Met5]enkephalin decreases blood pressure and heart rate. The site(s) and the mechanism of the hypotensive effects of the peptide are not known. The main purpose of this study was to test the hypothesis that [Met5]enkephalin dilates specifically a certain vascular bed which may account for the hypotensive effect of the peptide. Anesthetized male rabbits were instrumented for the measurement of blood pressure, heart rate, electrocardiogram and renal nerve activity. Four different microspheres (15 microns) were infused into the left ventricle in 10-15 s in either saline or with [Met5]enkephalin (1 mg/kg). Upon completion of the last microsphere injection the animals were killed and 35 tissues samples were taken for the determination of blood flow. Blood flows to many organs such as brain, glandular and cardiac tissues were not altered significantly by [Met5]enkephalin. However, [Met5]enkephalin increased blood flow to skeletal muscular bed. The increase in muscle blood flow was antagonized by naloxone, a specific opioid antagonist. These results suggest that the hypotensive action of [Met5]enkephalin in anesthetized rabbit is in part due to its vasodilatory effect in skeletal muscle.

Kinetic analysis of cardiac beta-receptors in perfused working rabbit hearts.

Myocardial adrenergic beta-receptors were isolated and partially purified from the nonischemic perfused working rabbit hearts. Using highly radioactive beta-receptor antagonist, dihydroalprenolol (DHA), properties of beta-receptors were investigated by kinetic equilibrium analysis when the physiological function of the heart appeared to be normal. At the concentration of 10 nM DHA dissociation constant (Kd) was 14.9 nM and there were at least two distinctly different DHA binding sites, based on the analysis of the dissociation rate of DHA-receptor complex. Identification of the two distinctly different DHA binding sites was not obvious from the analysis of Scatchard plot.

Suppression of sympathetic nerve activity by methionine enkephalin: additive interaction with clonidine in intact anesthetized rabbits.

In order to study the role of methionine enkephalin (met-enkephalin) in cardiovascular system, interaction between clonidine and met-enkephalin on the rate of sympathetic nerve discharge was investigated. In anesthetized rabbits multiunit renal nerve activity (RNA) was monitored after the treatment of met-enkephalin alone or met-enkephalin plus clonidine pretreatment. Met-enkephalin suppressed RNA, and reduced heart rate and blood pressure. Treatment of met-enkephalin after clonidine (2 to 20 micrograms/kg) increased the duration of RNA suppression. The data suggests that the cardiodepressive action of met-enkephalin is mediated by the stimulation of central presynaptic adrenergic alpha 2 receptor as proposed for clonidine.