Discovery of Highly Potent Liver X Receptor β Agonists

Introducing a uniquely substituted phenyl sulfone into a series of biphenyl imidazole liver X receptor (LXR) agonists afforded a dramatic potency improvement for induction of ATP binding cassette transporters, ABCA1 and ABCG1, in human whole blood. The agonist series demonstrated robust LXRβ activity (>70%) with low partial LXRα agonist activity (<25%) in cell assays, providing a window between desired blood cell ABCG1 gene induction in cynomolgus monkeys and modest elevation of plasma triglycerides for agonist 15. The addition of polarity to the phenyl sulfone also reduced binding to the plasma protein, human α-1-acid glycoprotein. Agonist 15 was selected for clinical development based on the favorable combination of in vitro properties, excellent pharmacokinetic parameters, and a favorable lipid profile.

Versatile synthesis and biological evaluation of novel 3'-fluorinated purine nucleosides

A unified synthetic strategy accessing novel 3'-fluorinated purine nucleoside derivatives and their biological evaluation were achieved. Novel 3'-fluorinated analogues were constructed from a common 3'-deoxy-3'-fluororibofuranose intermediate. Employing Suzuki and Stille cross-coupling reactions, fifteen 3'-fluororibose purine nucleosides 1-15 and eight 3'-fluororibose 2-chloro/2-aminopurine nucleosides 16-23 with various substituents at position 6 of the purine ring were efficiently synthesized. Furthermore, 3'-fluorine analogs of natural products nebularine and 6-methylpurine riboside were constructed via our convergent synthetic strategy. Synthesized nucleosides were tested against HT116 (colon cancer) and 143B (osteosarcoma cancer) tumor cell lines. We have demonstrated 3'-fluorine purine nucleoside analogues display potent tumor cell growth inhibition activity at sub- or low micromolar concentration.

Identification of a selective inverse agonist for the orphan nuclear receptor estrogen-related receptor alpha

The estrogen-related receptor alpha (ERRalpha) is an orphan receptor belonging to the nuclear receptor superfamily. The physiological role of ERRalpha has yet to be established primarily because of lack of a natural ligand. Herein, we describe the discovery of the first potent and selective inverse agonist of ERRalpha. Through in vitro and in vivo studies, these ligands will elucidate the endocrine signaling pathways mediated by ERRalpha including association with human disease states.

Regulation of PPARgamma coactivator 1alpha (PGC-1alpha) signaling by an estrogen-related receptor alpha (ERRalpha) ligand

Peroxisome proliferator-activated receptor gamma (PPARgamma) coactivator 1alpha (PGC-1alpha) is a transcriptional coactivator that is a key component in the regulation of energy production and utilization in metabolic tissues. Recent work has identified PGC-1alpha as a strong coactivator of the orphan nuclear receptor estrogen-related receptor alpha (ERRalpha), implicating ERRalpha as a potential mediator of PGC-1alpha action. To understand the role of ERRalpha in PGC-1alpha signaling, a parallel approach of high-throughput screening and gene-expression analysis was used to identify ERRalpha small-molecule regulators and target genes. We report here the identification of a potent and selective ERRalpha inverse agonist that interferes effectively with PGC-1alpha/ERRalpha-dependent signaling. This inverse agonist inhibits the constitutive activity of ERRalpha in both biochemical and cell-based assays. Also, we demonstrate that monoamine oxidase B is an ERRalpha target gene whose expression is regulated by PGC-1alpha and ERRalpha and inhibited by the ERRalpha inverse agonist. The discovery of potent and selective ERRalpha modulators and their effect on PGC-1alpha signaling provides mechanistic insight into gene regulation by PGC-1alpha. These findings validate ERRalpha as a promising therapeutic target in the treatment of metabolic disorders, including diabetes and obesity.

Antidepressant-like effects of kappa-opioid receptor antagonists in the forced swim test in rats

We showed previously that cAMP response element-binding protein (CREB) within the nucleus accumbens (NAc) of rats regulates immobility in the forced swim test (FST), an assay used to study depression. Because CREB regulates expression of dynorphin (which acts at kappa-opioid receptors) in NAc neurons, these findings raised the possibility that kappa-receptors mediate immobility behaviors in the FST. Here, we report that i.c.v. administration of the kappa-antagonist nor-binaltorphimine dose dependently decreased immobility in the FST, suggesting that it has antidepressant-like effects. Implicating a specific effect at kappa-receptors, similar antidepressant-like effects were seen after treatment with either of two novel, structurally dissimilar kappa-antagonists: 5'-guanidinonaltrindole, which was effective after i.c.v. but not systemic treatment, and 5'-acetamidinoethylnaltrindole (ANTI), which was potent and effective after systemic treatment. The behavioral effects of the kappa-antagonists resembled those of tricyclic antidepressants (desipramine) and selective serotonin reuptake inhibitors (fluoxetine and citalopram). Conversely, systemic administration of the kappa-agonist [5alpha,7alpha,8beta]-N-methyl-N-[7-[1-pyrrolidinyl]-1-oxaspiro[4.5]dec8-yl]-benzenacetamide (U-69593) dose dependently increased immobility in the FST, consistent with prodepressant-like effects. The effects of the kappa-ligands in the FST were not correlated with nonspecific effects on locomotor activity. Furthermore, the most potent and effective kappa-antagonist (ANTI) did not affect the rewarding impact of lateral hypothalamic brain stimulation at a dose with strong antidepressant-like effects. These findings are consistent with the hypothesis that CREB-mediated induction of dynorphin in the NAc "triggers" immobility behavior in the FST. Furthermore, they raise the possibility that kappa-antagonists may have efficacy as antidepressants, but lack stimulant or reward-related effects.

Potent and selective indolomorphinan antagonists of the kappa-opioid receptor

The indole moiety in the delta-opioid antagonist, naltrindole (2, NTI), was employed as a scaffold to hold an "address" for interaction with the kappa-opioid receptor. The attachment of the address to the 5'-position of the indole moiety was based on superposition of NTI upon the kappa antagonist, norbinaltorphimine (1, norBNI). A variety of cationic groups were employed as a kappa address in an effort to investigate its interaction with the anionic address subsite, Glu297, on the kappa receptor. Some of the groups that were employed for this purpose were amines, amidines, guanidines, and quaternary ammonium. Members of the series were found to have a varying degree of kappa antagonist potency and kappa selectivity when tested in smooth muscle preparations. The 5'-guanidine derivative 12a (GNTI) was the most potent member of the series and had the highest kappa selectivity ratio. GNTI was 2 times more potent and 6-10-fold more selective than norBNI (1). In general, the order of potency in the series was: guanidines > amidines approximately quaternary ammonium > amines. The kappa antagonist potency appeared to be a function of a combination of the pK(a) and distance constraint of the cationic substituent of the ligand. Receptor binding studies were qualitatively in agreement with the pharmacological data. Molecular modeling studies on 12a suggested that the protonated N-17 and guanidinium groups of GNTI are associated with Asp138 (TM3) and Glu297 (TM6), respectively, while the phenolic hydroxyl may be involved in donor-acceptor interactions with the imidazole ring of His291. It was concluded that the basis for the high kappa selectivity of GNTI is related both to association with the nonconserved Glu297 residue and to unfavorable interactions with an equivalent position in mu- and delta-opioid receptors.

Influence of organic modifier concentration on plate number in micellar electrokinetic chromatography. 1. 2-propanol

This paper establishes a physicochemical basis for the efficiency losses in micellar electrokinetic chromatography in buffers containing sodium dodecyl sulfate (SDS) and 2-propanol (2PN). Weakly, intermediately, and strongly retained analytes were separated in phosphate/borate buffers containing 50 mM SDS and from 0 to 10% 2PN by volume. Their plate numbers N generally agreed well with predictions of a theory for N based on longitudinal diffusion and instrumental contributions to dispersion. The N's of weakly and intermediately retained analytes were not affected strongly by 2PN over this concentration range, because their diffusion coefficients varied inversely with buffer viscosity and their retention times largely varied directly with viscosity. These combined effects on dispersion almost canceled. However, the N's of strongly retained analytes decreased with increasing 2PN, because their diffusion coefficients varied inversely with viscosity but their retention times increased more rapidly than did viscosity. These combined effects on dispersion did not cancel. These differences occurred because 2PN penetrated the micelles, caused bound counterions to be released, and increased the micellar charge and electrophoretic mobility. As 2PN concentration increased, the micelles electrophoresced increasingly rapidly against the electroosmotic flow. Consequently, strongly retained compounds required increasingly long times to elute.

Effect of a chemical modification on the hydrated adenosine intermediate produced by adenosine deaminase and a model reaction for a potential mechanism of action of 5-aminoimidazole ribonucleotide carboxylase

Using the hydrated adenosine intermediate (6R)-6-amino-1, 6-dihydro-6-hydroxy-9-(beta-D-ribofuranosyl)purine (2) produced by adenosine deaminase (ADA, EC 3.5.4.4) as a starting point, the active site probe and inhibitor platform 5-(formylamino)imidazole riboside (FAIRs, 4) was designed by removal of the-C6(OH)(NH2)-molecular fragment of 2 generated by the early events of the enzyme-catalyzed hydrolysis. FAIRs was synthesized directly from the sodium salt of 5-amino-1-(beta-D-ribofuranosyl)imidazole-4-carboxylic acid (CAIR) along a reaction sequence involving a tandem N-formylation/decarboxylation that may have a mechanistic connection to the Escherichia coli purE-catalyzed constitutional isomerization of N5-CAIR to CAIR. The physical and spectral properties of FAIRs were elucidated, its X-ray crystal and NMR solution structures were determined, and its interaction with ADA was investigated. Crystalline FAIRs exists solely as the Z-formamide rotamer and exhibits many of the same intramolecular hydrogen bonding events known to contribute to the association of Ado to ADA. In water and various organic solvents, however, FAIRs exists as NMR-distinct, slowly interconverting Z and E rotamers. This truncated enzymatic tetrahedral intermediate analog was determined to be a competitive inhibitor of ADA with an apparent Ki binding constant of 40 microM, a value quite close to that (33 microM) of the natural substrate's K(m). The actual species selected for binding by ADA, though, is likely the minor hydroxyimino prototropic form of Z-FAIRs possessing a far lower true Ki value. As the structural features of FAIRs appear well-suited to support its use as a template for constructing active site probes of both ADA and AIR carboxylases, a variety of carbohydrate-protected versions of FAIRs suitable for facile aglycon elaborations were synthesized. The N3-alkylation, N3-borane complexation, and C4-iodination of some of these were investigated in order to assess physicochemical properties that may assist in the elucidation of mechanisms for the AIR carboxylases. The survey of these properties taken together with a reasonable mechanism for the model CAIRs-->FAIRs synthetic transformation is interpreted to support a mechanism for the purE-catalyzed N5-CAIR-->CAIR biosynthetic one that involves a carboxylative sp3-rehybridization of the imidazole C4 atom rather than one possessing a dipole-stabilized C4 sp2 carbanionic intermediate.

Relationship of 133Xe cerebral blood flow to middle cerebral arterial flow velocity in men at rest

Cerebral blood flow (CBF) was measured by 133Xe clearance simultaneously with the velocity of blood flow through the left middle cerebral artery (MCA) over a wide range of arterial PCO2 in eight normal men. Average arterial PCO2, which was varied by giving 4% and 6% CO2 in O2 and by controlled hyperventilation on O2, ranged from 25.3 to 49.9 mm Hg. Corresponding average values of global CBF15 were 27.2 and 65.0 ml 100 g min-1, respectively, whereas MCA blood-flow velocity ranged from 42.8 to 94.2 cm/s. The relationship of CBF to MCA blood-flow velocity over the imposed range of arterial PCO2 was described analytically by a parabola with the equation: CBF = 22.8 - 0.17 x velocity + 0.006 x velocity2 The observed data indicate that MCA blood-flow velocity is a useful index of CBF response to change in arterial PCO2 during O2 breathing at rest. With respect to baseline values measured while breathing 100% O2 spontaneously, percent changes in velocity were significantly smaller than corresponding percent changes in CBF at increased levels of arterial PCO2 and larger than CBF changes at the lower arterial PCO2. These observed relative changes are consistent with MCA vasodilation at the site of measurement during exposure to progressive hypercapnia and also during extreme hyperventilation hypocapnia.

Human tolerance and physiological responses to exercise while breathing oxygen at 2.0 ATA

Multiple physiological functions were monitored in ten men who performed two 30-min periods of 150-W ergometer exercise during 120-min exposures to O2 at 2.0 ATA. There were no convulsions or electroencephalographic manifestations of increased excitability. Sequential measurements of peripheral visual fields, pulmonary mechanical function, mental performance, and cardiovascular function during the resting recovery after each of the two exercise periods were not detectably altered from pre-exercise control values. Pre- and post-exposure measurements of visual acuity, accommodation, pupil diameter, visual cortical activity, and retinal electrical activity also revealed no significant differences. While CNS symptoms were absent, average arterial PCO2 rose by about 5 mm Hg during both exercise periods. This finding was confirmed in six subjects who performed four 6-min periods of continuous exercise at 50, 100, 150, and 200 W while breathing O2 at 2.0 ATA. Average arterial PCO2 rose nearly linearly from 34.3 mm Hg at rest to 44.0 mm Hg at 200 W. Arterial PCO2-related increments in brain blood flow and PO2 may explain part or all of the known detrimental influence of exercise on CNS O2 tolerance.

Correlative study of behavior and synaptic events during halothane anesthesia in the lamprey

Behavioral anesthetic effects of halothane were compared with neurophysiological data obtained from monosynaptically coupled, single axon-giant neuron pairs in the isolated central nervous system of the lamprey in vitro. Based on the assumption that the number of halothane molecules at the site of anesthetic action is determined by molar concentration of the bath, depths of anesthesia were characterized in terms of synaptic events. The concentration producing anesthesia in 50% (AC50) and 95% (AC95) of the animals were 0.32 and 0.51 mM, respectively. With these concentrations, the depression of glutamate (GLUT)-mediated synaptic excitation remained less than 50%. Maximum suppression of the excitatory synaptic transmission was observed in the presence of 1.7 mM halothane which would be equivalent to the inhalation of 5.5% of this agent at 37 degrees C. At these concentrations, postsynaptic membranes did not respond to the bath-applied GLUT agonists. The decrease of agonist-induced responses to almost the same extent as excitatory postsynaptic potential (EPSP) amplitudes in the presence of halothane argues against a presynaptic mechanism affecting transmitter release. Persistent voltage-gated Na+ channel function at concentrations less than 2.4 mM is evidence against the involvement of this mechanism at these levels of anesthesia. The present results suggest that with depths between AC50 and AC95, anesthesia is associated with a partial reduction of sensitivity of the postsynaptic membrane to the excitatory amino acid transmitters.

Endothelium-dependent increase in vascular sensitivity to phenylephrine in long-term streptozotocin diabetic rat aorta

1. The effect of short- and long-term streptozotocin (STZ)-induced diabetes (12 and 52 weeks) on the vascular response to phenylephrine was examined in the isolated thoracic aorta with and without intact endothelium from diabetic, age matched control rats and diabetic rats treated with insulin. 2. Twelve weeks after induction of diabetes, aortae with intact endothelium demonstrated no changes either in sensitivity (defined as pD2) or contractility (defined as the maximal developed tension per aortic tissue wet weight) to phenylephrine. 3. In contrast, 52 weeks after induction of diabetes, aortae with intact endothelium demonstrated an increased sensitivity to phenylephrine while contractility to phenylephrine was not changed. Insulin treatment partially corrected the increased sensitivity to phenylephrine observed in diabetic rat aorta. 4. Removal of endothelium abolished the difference in phenylephrine sensitivity between diabetic and control aortae at 52 weeks. 5. Pretreatment of intact aortae with methylene blue, an inhibitor of endothelium-derived relaxing factor (EDRF), abolished the difference in phenylephrine sensitivity between control and diabetic rat aortae at 52 weeks, while pretreatment with indomethacin, an inhibitor of cyclo-oxygenase, had no effect. These results suggest that decreases in production or release of EDRF might be responsible for the increased vascular sensitivity to phenylephrine observed in long-term STZ diabetic rats. 6. Acetylcholine-induced relaxation, which is EDRF-dependent, was less in diabetic rat aortae with intact endothelium at 52 weeks, but not at 12 weeks. These results further support the theory that decreases in capacity of the endothelium to synthesize or release EDRF may occur in long-term STZ diabetic rats.

Comparison of the anesthetic requirement for tolerance of laryngeal mask airway and endotracheal tube

We tested the hypothesis that the laryngeal mask airway (LMA) is tolerated at lighter levels of anesthesia than an endotracheal tube (ET). We studied 20 unpremedicated, nonsmoking ASA physical status I or II patients aged 18-40 yr whose surgery lasted > 1 h. Subjects were randomly assigned to receive either an ET or LMA. Anesthesia was induced with intravenous propofol and the LMA or ET was inserted. The ET-group patients received 1.5 mg/kg of succinylcholine, preceded by vecuronium (0.015 mg/kg IV). Maintenance of anesthesia was with only isoflurane and approximately 66% N2O in O2 by spontaneous ventilation. All gas concentrations were measured by a Raman spectrometer sampling from the breathing circuit end of the LMA or ET. Toward the end of the procedure, the end-tidal N2O and isoflurane concentrations were allowed to decrease to < 3 vol% and 0.8 +/- 0.05 vol%, respectively. The end-tidal isoflurane concentration was then decreased in 0.1% +/- 0.05% decrements, each stable value being held for 5 min. The patient was observed for signs of reaction to the presence of the LMA or ET. The mean (range) end-tidal isoflurane concentrations for reaction to ET and LMA were 0.55% (0.4-0.7) and 0.35% (0.2-0.51), respectively (P < 0.001). These data confirm the original hypothesis of the study.

Controlled substance dispensing and accountability in United States anesthesiology residency programs

Controlled substance dependence (CSD) among anesthesiology personnel, particularly residents, has become a matter of increasing concern. Opinions vary as to the effectiveness of controlled substances (CS) accountability in deterring, identifying, or confirming CSD. A survey of program directors of American anesthesiology training programs was conducted in the summer of 1990 to determine the level of CS dispensing and accountability within their programs. The survey demonstrated that CS dispensing and accountability varied considerably among programs, among hospitals associated with individual programs, and within geographically distinct anesthesia delivery areas within the separate hospitals. Nevertheless, most institutions were moving toward improved methods of CS dispensing and providing more and better CS accountability. The presence of significant CSD, particularly among anesthesiology residents, was reconfirmed. We were unable to correlate the level of accountability of CS with the incidence of CSD. It remains to be seen to what extent CS accountability will continue to develop and whether CSD prevalence will then be changed.

[Enhanced myocardial depression from bupivacaine in diabetic rats]

We examined the direct effects of bupivacaine on the diabetic rat myocardium using an isolated perfused (Langendorff) heart preparation. Rats were made diabetic by injection of streptozotocin (55 mg.kg-1, i. v.). 12 weeks after the administration of streptozotocin, hearts were excised and perfused using Langendorff technique. Following 60 min for equilibration, diabetic hearts from the 12-week animals exhibited significant bradycardia. Bupivacaine 3 mcg.ml-1 did not decrease myocardial contractility in control animals. However, 3 mcg.ml-1 bupivacaine decreased contractility significantly in diabetic animals at nearly all periods. Bupivacaine decreased heart rate and coronary flow significantly and similarly in control and diabetic rats hearts. After pacing at 4 Hz, bupivacaine decreased contractility more in diabetic group than in control group. These results indicate that the presence of a diabetic state appears to enhance the sensitivity of the heart to the myocardial depressant effect of bupivacaine.

Recovery from general anesthesia

The pattern of recovery from anesthesia is ordinarily quite predictable. Using a limited number of drugs to provide anesthesia further improves predictability; it is more difficult to assign a cause for delayed emergence when multiple agents have been administered. We believe the recovery period is often more difficult to manage safely than induction and maintenance of anesthesia. During this phase, the effects of surgical trauma are superimposed on the patient's preexisting disease state, the anesthetic level is changing rapidly, respiratory function has not returned to normal, and circulatory reflexes may not have been regained. Because the patient is being moved from the operating room and care of the patient is being transferred from one person or team to others, vigilance and treatment may also be impaired. It is a period of care that warrants further study.

1H NMR study of the solution structure of the self-complementary dodecanucleotide d(TGCA)3

The deoxyoligonucleotide d(TGCA)3 is a candidate for exhibiting unusual conformations. Its 1H NMR spectrum under low salt conditions has been obtained at 400 MHz and assigned using two-dimensional NMR techniques. The sugar puckers and glycosidic torsions have been determined by inspecting the relative intensities of the intranucleotide NOEs and COSY crosspeaks. At low electrolyte concentration (100 mM NaCl) the molecule exists as a right-handed duplex with twelve Watson-Crick base-pairs and deoxyribose moieties assuming the O1'-endo to C1'-exo pucker.

Isoflurane: an anesthetic for the eighties?

The introduction of isoflurane to clinical practice follows the search for a nonflammable, potent inhalation anesthetic which, above all, is chemically stable so as to resist biodegradation or attack by other chemicals. These attributes characterize isoflurane (Table 2). The hoped for freedom from hepatic and renal toxicity and from carcinogenic and mutagenic properties is a reality with this drug. Other favorable characteristics include relatively low solubility in blood in relation to anesthetic dose, lack of arrhythmogenic effect, provision of good muscle relaxation, and the absence of central nervous system excitation. Its moderate pungency detracts slightly from the ease of inhaled induction. Disadvantages include respiratory depression, reduced arterial blood pressure, uterine relaxation, decreased uteroplacental blood flow, and likely ability to trigger malignant hyperpyrexia. The frequency and/or significance of tachycardia and dilation of muscle blood vessels in clinical practice remain to be established. We believe isoflurane is a significant improvement over earlier potent inhalation anesthetics.

Sister chromatid exchanges induced by inhaled anesthetics

There is sufficient evidence that anesthetics may cause cancer to justify a test of their carcinogenic potential. Baden, et al., using the Ames test, a rapid and inexpensive genetic indicator of carcinogenicity, have shown that among currently used anesthetics fluroxene alone caused bacterial mutations. The authors used the sister chromatid exchange (SCE) technique, another rapid assay of mutagenic-carcinogenic potential. The frequency of sister chromatid exchanges in Chinese hamster ovary cells increases when the cell cultures are exposed to mutagen-carcinogens, particularly in the presence of a metabolic activating system. With this test system a one-hour exposure to 1 MAC nitrous oxide, diethyl ether, trichloroethylene, halothane, enflurane, isoflurane, methoxyflurane, or chloroform did not increase SCE values. Divinyl ether, fluroxene and ethyl vinyl ether increased SCE values in the same circumstances. Results of this study of mammalian cells suggest that no currently used anesthetic is a mutagen-carcinogen. The results also suggest that anesthetics containing a vinyl moiety may be mutagen-carcinogens.

Enflurane and methoxyflurane metabolism at anesthetic and at subanesthetic concentrations

In an attempt to determine the importance of concentration of an anesthetic agent as a determinant of the extent of its biotransformation, we measured fluoride excretion in groups of Fischer 344 rats treated with one of several subanesthetic or an anesthetic concentration (1 MAC) of either enflurane or methoxyflurane. Anesthetic administrations (2.0% enflurane or 0.26% methoxyflurane) ranged from 0.15 hours (9 minutes) to 4.8 hours. Subanesthetic exposures, all of 48 hours duration, ranged in concentration from 0.2% enflurane to 0.0016% methoxyflurane. Greatest metabolism occurred at the lowest concentration time (MAC-hours) of subanesthetic administrations and at the shortest duration of anesthetic exposure. Increasing time in the case of anesthetizing exposures, or concentration in subanesthetic exposures, increased the amount of metabolite produced. However, the increased production of metabolite was not proportional to the increase of concentration or duration of exposure. Enzyme induction was ruled out as an important factor in the larger amount of metabolism seen during the subanesthetic exposures. Therefore, the exposure of a patient to the metabolites of an anesthetic is actually low although the anesthetic is administered at a high concentration.

A test of the carcinogenicity of enflurane, isoflurane, halothane, methoxyflurane, and nitrous oxide in mice

We exposed Swiss ICR mice for 2-hour periods to 1/32, 1/8 and/or 1/2 MAC enflurane, halothane, isoflurane, methoxyflurane, or N2O both in utero during the last 1/2 of pregnancy (4 exposures at 2-day intervals) and after delivery (24 exposures at 2-to-3-day intervals). Anesthetics were delivered in air or in O2. Thus, 1973 mice were exposed and examined after 15 months of life for the development of neoplastic lesions. Neoplastic lesions (principally pulmonary adenomas, lymphomas, hepatocyte lesions, liver vascular lesions) were found in all treatment and control sets. There was no indication that a specific anesthetic or anesthetic dose was carcinogenic. Our results do not confirm the suggestion that isoflurane is a hepatocarcinogen, nor do our data suggest that the modern inhaled anesthetics pose a significant threat of carcinogenicity.

Hypotensive anesthesia for total hip arthroplasty: a study of blood loss and organ function (brain, heart, liver, and kidney)

The authors attempted to determine whether hypotensive anesthesia or the method of inducing hypotension has any effect on postoperative brain, liver, or kidney function and myocardial status following total hip arthroplasty. Thirty patients were anesthestized with halothane-nitrous oxide for total hip arthroplasty and randomly assigned to one of three groups. In two groups mean arterial blood pressure was decreased to 50 torr by high inspired concentrations of halothane (n = 90) or sodium nitroprusside (n = 12). In the third group (n = 9) mean blood pressure was maintained within 20% of control. Intraoperative blood losses decreased from 1,183 +/- 172 ml in the normotensive group to 406 +/- 102 ml and 326 +/- 41 ml in the halothane and nitroprusside hypotensive groups, respectively. Neither method of inducing hypotension nor hypertensive technique affected the results of postoperative tests of cerebral, hepatic, or renal function and myocardial status. These tests were performed before anesthesia and operation and at intervals in the postoperative course. In this small group of patients, deliberate hypotension for total hip arthroplasty added no morbidity and significantly shortened operating time, decreased blood loss, and decreased the number of blood transfusions needed.

Comparative toxicities of enflurane, fluroxene and nitrous oxide at subanaesthetic concentrations in laboratory animals

We compared the toxicities of subanesthetic concentrations of fluroxene, enflurane and nitrous oxide in mice, rats and guinea pigs which were in an active growth phase. Fluroxene produced a greater mortality and decrement in weight gain than enflurane and nitrous oxide despite administration of far lower concentrations. Enflurane, 0.1 MAC, resulted in a detrimental effect on weight and early mortality in mice but not in rats or guinea pigs. Nitrous oxide, 0.1 MAC, resulted in only a minor effect on weight gain in guinea pigs and an increased incidence of focal inflammatory liver changes in mice. No consistent injury to any organs other than liver or kidney were found.

Species, strain, sex and individual differences in enflurane metabolism

Species, sex and individual differences in serum inorganic fluoride concentrations were demonstrated in mice, guineapigs and rats exposed to either 0.07% or 0.2% enflurane for 35 days, suggesting differences in enflurane biotransformation. Exposure of Fischer 344 rats and Sprague-Dawley rats to 0.2% enflurane for 8 days resulted in enzyme induction as demonstrated by increasing serum inorganic fluoride and cytochrome P-450 concentrations. However, there was no difference in cytochrome P-450 concentrations between the strains despite differences in inorganic fluoride concentration. These results emphasize the multiplicity of factors and the lack of predictability in patterns of enflurane metabolism among species, strains and individuals.

Psychological eff-cts of halothane and isoflurane anesthesia

Psychological effects of halothane (16 subjects) and isoflurane (24 subjects) anesthesia on healthy young men were assessed prior to and 2,3,4,6,8, and 30 days after anesthesia. The results with each agent were compared with each other and with the results for 41 unanesthetized controls. Both agents altered psychological function. Changes in function were greatest 2 days after anesthesia; function had returned to near preanesthesia values 8 days after anesthesia. Only slight symptom and mood effects and no intellectual effect attributable to anesthesia remained 30 days after anesthesia. Halothane produced greater negative effects on moodds and symptoms and tended to produce greater negative effects on intellectural function than did isoflurane. The differences between the two anesthetics are consistent with differences in their solubilities and metabolism.

Comparative toxicities of halothane, isoflurane, and diethyl ether at subanesthetic concentrations in laboratory animals

Effects of 35-day exposures to subanesthetic concentrations of halothane, isoflurane, and diethyl ether were measured in mice, rats, and guinea pigs which were in a phase of rapid body growth. Halothane produced a greater decrement in weight gain and a greater incidence of hepatic degenerative changes than isoflurane or diethyl ether despite its administration at lower anesthetic concentrations. Isoflurane results were intermediate between those of halothane and diethyl ether. No consistent injury to any organ other than the liver was found.