Regulation of glucose transporters GLUT-4 and GLUT-1 gene transcription in denervated skeletal muscle

Because GLUT-4 expression is decreased whereas GLUT-1 expression is increased in denervated skeletal muscle, we examined the effects of denervation on GLUT-4 and GLUT-1 gene transcription. The right hindlimb skeletal muscle of male transgenic mice containing sequential truncations (2,400, 1,639, 1,154, and 730 bp) of the human GLUT-4 promoter linked to the chloramphenacol acyl transferase (CAT) gene was denervated, and the contralateral hindlimb was sham operated. RNase protection analysis revealed that after 72 h denervation decreased CAT mRNA and GLUT-4 mRNA levels 64-85%, respectively (P < 0.05), in the gastrocnemius muscles. In contrast, denervation of the right hindlimb of male rats increased GLUT-1 gene transcription and GLUT-1 mRNA levels by 94 and 213%, respectively (P < 0.05). In conclusion, GLUT-4 transcription is decreased but GLUT-1 transcription is increased in denervated skeletal muscle, suggesting that the effects of denervation on GLUT-4 and GLUT-1 expression are, in part, transcriptionally mediated. Furthermore, these data indicate that a DNA sequence regulated by denervation is located within 730 bp of the 5'-flanking promoter region of the human GLUT-4 gene.

New findings of the correlation between acupoints and corresponding brain cortices using functional MRI

A preliminary study of the correlation between acupuncture points (acupoints) for the treatment of eye disorders suggested by ancient Oriental literature and the corresponding brain localization for vision described by Western medicine was performed by using functional MRI (fMRI). The vision-related acupoint (VA1) is located in the lateral aspect of the foot, and when acupuncture stimulation is performed there, activation of occipital lobes is seen by fMRI. Stimulation of the eye by directly using light results in similar activation in the occipital lobes by fMRI. The experiment was conducted by using conventional checkerboard 8-Hz light-flash stimulation of the eye and observation of the time-course data. This was followed by stimulation of the VA1 by using the same time-course paradigm as visual light stimulation. Results obtained with 12 volunteers yielded very clean data and very close correlations between visual and acupuncture stimulation. We have also stimulated nonacupoints 2 to 5 cm away from the vision-related acupoints on the foot as a control, and activation in the occipital lobes was not observed. The results obtained demonstrate the correlation between activation of specific areas of brain cortices and corresponding acupoint stimulation predicted by ancient acupuncture literature.

Regulation of glucose transporter GLUT-4 and hexokinase II gene transcription by insulin and epinephrine

Transport of glucose across the plasma membrane by GLUT-4 and subsequent phosphorylation of glucose by hexokinase II (HKII) constitute the first two steps of glucose utilization in skeletal muscle. This study was undertaken to determine whether epinephrine and/or insulin regulates in vivo GLUT-4 and HKII gene transcription in rat skeletal muscle. In the first experiment, adrenodemedullated male rats were fasted 24 h and killed in the control condition or after being infused for 1.5 h with epinephrine (30 microg/ml at 1.68 ml/h). In the second experiment, male rats were fasted 24 h and killed after being infused for 2.5 h at 1.68 ml/h with saline or glucose (625 mg/ml) or insulin (39.9 microg/ml) plus glucose (625 mg/ml). Nuclei were isolated from pooled quadriceps, tibialis anterior, and gastrocnemius muscles. Transcriptional run-on analysis indicated that epinephrine infusion decreased GLUT-4 and increased HKII transcription compared with fasted controls. Both glucose and insulin plus glucose infusion induced increases in GLUT-4 and HKII transcription of twofold and three- to fourfold, respectively, compared with saline-infused rats. In conclusion, epinephrine and insulin may regulate GLUT-4 and HKII genes at the level of transcription in rat skeletal muscle.

Transcriptional regulation of hexokinase II in denervated rat skeletal muscle

Hexokinase II protein is augmented in denervated skeletal muscle; therefore, we determined if hexokinase II gene transcription rates and mRNA levels are increased with denervation. The right hindlimb skeletal muscles of male rats were denervated while the left hindlimbs were sham operated. Seventy-two h following surgery, rats were sacrificed and the gastrocnemius and soleus muscles were harvested for nuclear and RNA isolation. Nuclear run-on and ribonuclease protection analyses indicated that denervation increased hexokinase II transcription rates and mRNA levels 42% and 88%, respectively (p < 0.05). Total hexokinase activity rose 23% in denervated gastrocnemius muscle. In conclusion, the increase in hexokinase II gene transcription and mRNA may account for the increase in hexokinase II protein and the subsequent rise in total hexokinase activity in denervated rat skeletal muscle.

Intramolecular isotope effects for benzylic hydroxylation of isomeric xylenes and 4,4'-dimethylbiphenyl by cytochrome P450: relationship between distance of methyl groups and masking of the intrinsic isotope effect

Intramolecular isotope effects associated with the benzylic hydroxylation of a series of selectively deuterated isomeric xylenes and 4,4'-dimethylbiphenyl as catalyzed by various rat liver microsomal preparations and CYP2B1 were determined. Substrate analogs in which each methyl group contained either one (d2 substrates) or two (d4 substrates) deuterium atoms were used to determine the intrinsic isotope effect for the reaction. Specific values of the individual primary (P) and secondary isotope effects (S) were determined. P ranged from a low of 5.32 +/- 0.48 to a high of 7.57 +/- 0.42 depending upon the specific cytochrome P450 preparation used for catalysis. S had an average value of 1.03. The d3 substrates allowed exploration of the effect of distance on the magnitude of the observed isotope effect. The results indicate that the distance of 6.62 A that separates the carbon atoms of the para methyl groups of p-xylene is insufficient to suppress (mask) the intrinsic isotope effect for benzylic hydroxylation by all of the enzyme preparations examined. Conversely, a distance of 11.05 A, the minimal separation between the carbon atoms of the para methyl groups of p,p'-dimethylbiphenyl, is large enough to almost completely mask the intrinsic isotope effect for benzylic hydroxylation by the same set of enzymes.

Quantitative estimation of ultrasonographic attenuation in the myocardium using conventional echocardiographic instrumentation

Through the careful and judicious use of the time gain controls in conventional echocardiographic instrumentation, we have found that it is possible to obtain quantitative estimates of the attenuation of ultrasound beams even in vivo. These estimates are based on the quantitative comparison of the amplitude of the echo waveforms at different depths. Here, we report on such attenuation measurements using both a tissue phantom and the interventricular septum of the myocardium in vivo. The in vitro estimates of attenuation with this method are in agreement with independent laboratory measurements of the same parameter. In vivo measurements on the myocardium indicate oscillations in the magnitude of the attenuation over the heart cycle and suggest methods for the quantitative assessment of a variety of pathologic conditions in the myocardium noninvasively using conventional ultrasound scanners.

Effects of thyroid hormone on GLUT4 glucose transporter gene expression and NIDDM in rats

Previous studies have shown that T3 coordinately stimulates GLUT4-glucose transporter messenger RNA (mRNA) and protein expression in mixed fiber-type skeletal muscle of the rat and produces a concomitant elevation in basal (noninsulin mediated) glucose uptake. The aim of the present study was to 1) determine the precise mechanism(s) for the T3-induced expression of GLUT4 in skeletal muscle, and 2) investigate the potential benefits of T3 on noninsulin dependent diabetes mellitus (NIDDM). Ten daily ip injections of T3 (100 micrograms/100 g BW) administered to hypothyroid male Sprague-Dawley rats, increased both GLUT4 mRNA and transcription approximately 70% (P < 0.05) in mixed fiber-type hindlimb skeletal muscle. Transcriptional induction was subsequently defined to be restricted to red (oxidative) muscle fibers (2.5-fold; P < 0.05), whereas GLUT4 protein was increased in both red and white (glycolytic) skeletal muscle. GLUT4 mRNA and protein expression were similarly inducible in the skeletal muscle of insulin-resistant Zucker rats. More importantly, T3 treatment totally ameliorated hyperinsulinemia in obese animals (P < 0.001), although their moderately elevated plasma glucose levels were not significantly altered. In conclusion, regulation of GLUT4 expression by T3 was shown to lie at the transcriptional level in red skeletal muscle, whereas in white muscle fiber types, it appears to operate via an alternative posttranscriptional mechanism. These data also support the potential of hormonally inducing glucose transporter expression in insulin-resistant muscle. However, high levels of T3 are associated with a number of adverse side-effects, in particular the stimulation of hepatic gluconeogenesis. Nevertheless, future studies may demonstrate, e.g. subthyrotoxic levels, to be similarly effective but without side effects, and thus perhaps find a clinical application in reducing both hyperinsulinemia and hyperglycemia in NIDDM.

Prenatal nicotine effects on memory in rats: pharmacological and behavioral challenges

Cigarette smoking during pregnancy has been shown in a variety of studies to be associated with cognitive deficits in the children. Nicotine administration to rats during gestation has been found to cause subtle cognitive effects in the offspring. Some individual differences in cognitive impairment may be related to prenatal nicotine effects on noradrenergic (NE) systems. In the current study, 10 Sprague-Dawley rat dams were infused with approximately 2 mg/kg/day of nicotine ditartrate via osmotic minipumps and 10 control dams were exposed to vehicle-containing minipumps from gestational day (GD) 4-20. Starting on postnatal day (PND) 50, the offspring were tested for T-maze rewarded spatial alternation with intertrial intervals of 0, 10, 20, or 40 s. There was a sex- and delay-dependent effect of prenatal nicotine exposure on T-maze alternation. Nicotine-exposed males showed a significant deficit at the 0 s delay. In radial-arm maze (RAM) acquisition training there were no significant nicotine effects. However, significant nicotine-related effects were seen with subsequent behavioral and pharmacological challenges in the RAM. Changing the RAM testing location to an identical maze in a different room elicited a significant choice accuracy deficit in the prenatal nicotine-exposed rats compared with controls. Acute nicotine challenge did not cause any differential effects in the prenatal nicotine and control groups. During the isoproterenol (beta-NE agonist) challenge phase there appeared a significant facilitation of choice accuracy and speeding of response in the prenatal nicotine exposure group which was not seen in the control group. The alpha-NE agonist phenylpropanolamine caused a significant deficit in control females but not in the females prenatally exposed to nicotine. No differential effects of the alpha-NE antagonist phenoxybenzamine were seen in the prenatal nicotine and control groups. Throughout RAM testing there was a significant sex effect with males having better choice accuracy than females. These results demonstrate that the persisting cognitive effects of prenatal exposure to 2 mg/kg/day cause subtle effects in cognitive performance which can be elicited with behavioral and pharmacological challenge. These results also support previous studies suggesting the involvement of NE systems in persisting effects of prenatal nicotine exposure.

Differential expression of ob mRNA in rat adipose tissues in response to insulin

The recently cloned obese (ob) gene encodes a fat-specific mRNA and a protein which is believed to regulate satiety and metabolic rate so as to control fat storage. In the present study we investigated rat ob mRNA levels in different fat depots and the effects of insulin infusion on ob mRNA expression. Northern blot analysis showed the abdominal fat (epididymal and perirenal fat pads) had higher ob mRNA levels than subcutaneous fat. After a 2.5-hr infusion of insulin into fasted rats, ob mRNA levels were increased by 3.0 and 1.9-fold in epididymal and perirenal fat pads, respectively. However, no change of ob mRNA level was observed in the subcutaneous fat depot. These data demonstrate adipose depot site-specific expression of ob mRNA and support the hypothesis that insulin plays an important role in the expression of ob mRNA.

Reaction of trifluoroacetaldehyde with amino acids, nucleotides, lipid nucleophiles, and their analogs

Trihaloacetaldehydes are used as sedatives, are key intermediates in the metabolism of 1,1,1,2-tetrahaloethanes, some of which are chlorofluorocarbon substitutes, and are metabolites of trihaloethanols, which are intestinal and bone marrow toxins. In the present study, trifluoroacetaldehyde was used as a model to examine the reactions of trihaloacetaldehydes with cellular nucleophiles, including amino acids, nucleotides, and lipid components. Reaction of trifluoroacetaldehyde hydrate (10 mM) with amino acids (100 mM) in buffer at pH 7.0 and 30 degrees C showed that only L-cysteine formed stable adducts, which were identified as (2R,4R)- and (2S,4R)-2-(trifluoromethyl)thiazolidine-4-carboxylic acid. The absolute stereochemistry of (2R,4R)- and (2S,4R)-2-(trifluoromethyl)thiazolidine-4-carboxylic acid was determined by homonuclear Overhauser effect experiments. The diastereoisomers were formed in a 2.8:1 ratio at 37 degrees C and in a 1:4.0 ratio at 80 degrees C. Trifluoroacetaldehyde also reacted with L-cysteine methyl ester and 2-mercaptoethylamine to form stable thiazolidine derivatives, but did not react with N-acetyl-L-cysteine. The reaction of trifluoroacetaldehyde with the amino groups of ATP, GMP, CMP, L-citrulline, and urea resulted in the formation of stable imines. TMP, which lacks an exocyclic amino group, did not react. Glutathione reacted with trifluoroacetaldehyde to form (2R,5R)- and (2S,5R)-5-amino-6-[carboxymethyl)imino]-2-(trifluoromethyl)-1,3- oxathiane, whose formation was accompanied by simultaneous cleavage of the glutamyl moiety. The reactivity of nucleophilic groups with trifluoroacetaldehyde follows the order SH > NH2 > OH. The results of the present study indicate that trifluoroacetaldehyde covalently modifies cellular nucleophiles. The biological significance of these reactions warrants further investigation. The reaction of trifluoroacetaldehyde with L-cysteine and glutathione may afford routes for the stereoselective synthesis of cysteine prodrugs and five- or six-membered heterocyclic compounds.

Metabolism of 1,2-dichloro-1-fluoroethane and 1-fluoro-1,2,2-trichloroethane: electronic factors govern the regioselectivity of cytochrome P450-dependent oxidation

1,2-Dichloro-1-fluoroethane (HCFC-141) and 1,1,2-trichloro-2-fluoroethane (HCFC-131) were chosen as models to study the regioselectivity of halogenated alkane metabolism. Metabolites in the urine of rats given HCFC-131 ip were the following: inorganic fluoride, chlorofluoroacetic acid, dichloroacetic acid, N-(2-hydroxyethyl)chlorofluoroacetamide, and three unidentified minor metabolites. In vitro incubation of HCFC-131 with either rat liver microsomes from pyridine-treated rats or expressed human cytochrome P450 2E1 isozyme in the presence of NADPH gave fluoride, chlorofluoroacetic acid, and dichloroacetic acid as metabolites. HCFC-141 was biotransformed in rats to inorganic fluoride, chlorofluoroacetic acid, 2-chloro-2-fluoroethanol, and 2-chloro-2-fluoroethyl glucuronide, which were detected in urine. Incubation of HCFC-141 with NADPH-fortified liver microsomes from pyridine-induced rats or expressed human cytochrome P450 2E1 afforded fluoride, chlorofluoroacetaldehyde hydrate, and chloroacetic acid as products. The metabolites identified were consistent with a cytochrome P450-dependent oxidation mechanism. The data also indicated that phosphatidylethanolamine may be a cellular target for chlorofluoroacetyl chloride, a reactive intermediate generated from HCFC-131 by cytochrome P450-dependent oxidation. Chlorofluoroacetic acid given to rats ip was largely recovered in the rat urine, although the formation of inorganic fluoride as a metabolite was observed. The mechanism of defluorination of chlorofluoroacetic acid is not clear. Regioselective oxidation by cytochrome P450 was observed between the two potential oxidizable sites in HCFC-141 and in HCFC-131. Comparison of the observed ratio of oxidation at different sites in in vitro experiments with the calculated activation energies for hydrogen-atom abstraction from these sites indicated that electronic factors are the primary determinant of regioselectivity. In vivo regioselectivity could not be compared with theory since this ratio does not reflect the true regioselectivity due to differences in excretion, reabsorption, secondary metabolism (e.g., fluoride generation from chlorofluoroacetic acid), other routes of fluoride formation, and limitation of the method of detection.

Designing safer chemicals: predicting the rates of metabolism of halogenated alkanes

A computational model is presented that can be used as a tool in the design of safer chemicals. This model predicts the rate of hydrogen-atom abstraction by cytochrome P450 enzymes. Excellent correlations between biotransformation rates and the calculated activation energies (delta Hact) of the cytochrome P450-mediated hydrogen-atom abstractions were obtained for the in vitro biotransformation of six halogenated alkanes (1-fluoro-1,1,2,2-tetrachloroethane, 1,1-difluoro-1,2,2-trichloroethane, 1,1,1-trifluro-2,2-dichloroethane, 1,1,1,2-tetrafluoro-2-chloroethane, 1,1,1,2,2,-pentafluoroethane, and 2-bromo-2-chloro-1,1,1-trifluoroethane) with both rat and human enzyme preparations: In(rate, rat liver microsomes) = 44.99 - 1.79(delta Hact), r2 = 0.86; In(rate, human CYP2E1) = 46.99 - 1.77(delta Hact), r2 = 0.97 (rates are in nmol of product per min per nmol of cytochrome P450 and energies are in kcal/mol). Correlations were also obtained for five inhalation anesthetics (enflurane, sevoflurane, desflurane, methoxyflurane, and isoflurane) for both in vivo and in vitro metabolism by humans: In[F(-)]peak plasma = 42.87 - 1.57(delta Hact), r2 = 0.86. To our knowledge, these are the first in vivo human metabolic rates to be quantitatively predicted. Furthermore, this is one of the first examples where computational predictions and in vivo and in vitro data have been shown to agree in any species. The model presented herein provides an archetype for the methodology that may be used in the future design of safer chemicals, particularly hydrochlorofluorocarbons and inhalation anesthetics.

Stereoselectivity and isotope effects associated with cytochrome P450-catalyzed oxidation of (S)-nicotine. The possibility of initial hydrogen atom abstraction in the formation of the delta 1', 5-nicotinium ion

The stereochemical course of cytochromes P450 [P4501A1, P4502B1, P4502B4, and P450101 (P450cam)] catalyzed alpha-carbon oxidations of the cis-(Z)- and trans-(E)-5'-d1 diastereomers of (S)-nicotine has been examined. All enzyme preparations led to the stereoselective abstraction of the 5'-hydrogen atom trans to the pyridine ring with P450101 and human liver microsomal preparations displaying the highest (90%) and P4502B1 the lowest (67%) degree of stereoselectivity. No isotope effect was detected for any of the enzyme-catalyzed reactions, although the existence of an intrinsic isotope effect was inferred by the observation of an intramolecular isotope effect of 2-2.6 observed for the N-demethylation of (S)-N'-dideuteromethylnornicotine. Evidence for P450101-catalyzed N'-oxidation was sought but could not be found at higher than trace levels. These results, together with those obtained by computational methods, are interpreted in terms of an alpha-carbon oxidative pathway involving hydrogen atom abstraction rather than single electron transfer as the initiating event in the P450-catalyzed oxidation of (S)-nicotine to its delta 1',5'-iminium ion metabolite.

Stereospecific activation of the procarcinogen benzo[a]pyrene: a probe for the active sites of the cytochrome P450 superfamily

It has been established previously that the sterochemistry of epoxidation of the procarcinogen benzo[a]pyrene determines the potency of the ultimate carcinogen. Herein we report that seven human P450s, five rodent P450s, and two bacterial P450s all convert B[a]P to the most potent carcinogenic often differ in both regioselectivity and stereoselectivity. This is likely due to the large size of the substrate molecule and its constraints in the active sites. Smaller substrates that can rotate more freely in the active site may be expected to have greater variations in binding orientations and therefore greater differences in stereoselectivities. Molecular mechanics is used to determine the specific amino acids responsible for the stereochemical outcome. Molecular dynamics is then used to strengthen the hypothesis that a single helical region, one that is likely to be conserved in all P450s, plays a primary role in determining the stereoselectivity of the reaction.

Potent inhibitors of human inosine monophosphate dehydrogenase type II. Fluorine-substituted analogues of thiazole-4-carboxamide adenine dinucleotide

Three analogues of thiazole-4-carboxamide adenine dinucleotide (TAD) (1-3) containing a fluorine atom at the C2' of the adenine nucleoside (in the ribo and arabino configuration) and at the C3' (in the ribo configuration) were synthesized in high yield from the corresponding 5'-monophosphates of 2'-deoxy-2'-fluoroadenosine (9), 9-(2-deoxy-2-fluoro-beta-D-arabinofuranosyl)-adenine (17), and 3'-deoxy-3'-fluoroadenosine (14), respectively. Pure 2',3'-O-isopropylidene-tiazofurin 5'-phosphorimidazolide (8) was obtained by phosphorylation of the protected tiazofurin followed by treatment with carbonyldiimidazole and HPLC purification. Reaction of 8 with 9 in DMF-d7 (monitored by 1H and 31P NMR) afforded the desired dinucleotide 12, which after deisopropylidenation gave 1 in 82% yield. Small amounts of symmetrical dinucleotides AppA (10, 7.2%) and TRppTR (11, 8.0%) were also isolated during HPLC purification of the major product 12. In a similar manner, compounds 2 and 3 were obtained by coupling of 8 with 14 and 17 in 80% and 76% yield, respectively. All newly prepared fluoro-substituted compounds as well as beta-CF2-TAD, earlier synthesized by us, showed good inhibitory activity against inosine monophosphate dehydrogenase type II, the isozyme which is predominant in neoplastic cells. Binding of 1 (Kis = 0.5 microM), 2 (Kis = 0.7 microM), and 3 (Kis = 2.9 microM) was comparable to that of TAD (Ki = 0.2 microM). The difluoromethylene bisphosphonate analogue, beta-CF2-TAD (Ki = 0.17 microM), was found to be equally effective as the best cofactor-type inhibitor, beta-CH2-TAD (Ki = 0.11 microM). Interestingly, the level of inhibition of horse liver alcohol dehydrogenase by these compounds was found to be much lower (0.1 mM for 1 and 2 and no inhibition up to 10 mM for 3). These findings show that inhibition of tumor-induced inosine monophosphate dehydrogenase type II is selective and may be of therapeutic interest.

Metabolism of 1-fluoro-1,1,2-trichloroethane, 1,2-dichloro-1,1-difluoroethane, and 1,1,1-trifluoro-2-chloroethane

1-Fluoro-1,1,2-trichloroethane (HCFC-131a), 1,2-dichloro-1,1-difluoroethane (HCFC-132b), and 1,1,1-trifluoro-2-chloroethane (HCFC-133a) were chosen as models for comparative metabolism studies on 1,1,1,2-tetrahaloethanes, which are under consideration as replacements for ozone-depleting chlorofluorocarbons (CFCs). Male Fischer 344 rats were given 10 mmol/kg ip HCFC-131a or HCFC-132b or exposed by inhalation to 1% HCFC-133a for 2 h. Urine collected in the first 24 h after exposure was analyzed by 19F NMR and GC/MS and with a fluoride-selective ion electrode for the formation of fluorine-containing metabolites. Metabolites of HCFC-131a included 2,2-dichloro-2-fluoroethyl glucuronide, 2,2-dichloro-2-fluoroethyl sulfate, dichlorofluoroacetic acid, and inorganic fluoride. Metabolites of HCFC-132b were characterized as 2-chloro-2,2-difluoroethyl glucuronide, 2-chloro-2,2-difluoroethyl sulfate, chlorodifluoroacetic acid, chlorodifluoroacetaldehyde hydrate, chlorodifluoroacetaldehyde-urea adduct, and inorganic fluoride. HCFC-133a was metabolized to 2,2,2-trifluoroethyl glucuronide, trifluoroacetic acid, trifluoroacetaldehyde hydrate, trifluoroacetaldehyde-urea adduct, inorganic fluoride, and a minor, unidentified metabolite. With HCFC-131a and HCFC-132b, glucuronide conjugates of 2,2,2-trihaloethanols were the major urinary metabolites, whereas with HCFC-133a, a trifluoroacetaldehyde-urea adduct was the major urinary metabolite. Analysis of metabolite distribution in vivo indicated that aldehydic metabolites increased as fluorine substitution increased in the order HCFC-131a < HCFC-132b < HCFC-133a. With NADPH-fortified rat liver microsomes, HCFC-133a and HCFC-132b were biotransformed to trifluoroacetaldehyde and chlorodifluoroacetaldehyde, respectively, whereas HCFC-131a was converted to dichlorofluoroacetic acid. No covalently bound metabolites were detected by 19F NMR spectroscopy.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of self-esteem and wellness in health promotion professionals

When researchers tested 90 wellness professionals attending the National Wellness Conference using the Adult Form of Coopersmith's Self-esteem Inventory and TestWell, participants scored above the norm on self-esteem and over-all wellness and on the subscales of Sexuality and Emotional Awareness, Safety, and Emotional Management. In addition, TestWell, a revised wellness inventory, showed internal reliability (alpha) of .84.

Dose-response study of intravenous torsemide in congestive heart failure

In a double-blind dose-response study, 49 patients with New York Heart Association functional class III or IV heart failure were randomized to receive a single intravenous dose of 5, 10, or 20 mg torsemide or 40 mg furosemide. Torsemide produced dose-related decreases in body weight and increases in sodium and chloride excretion and urine volume. With the 20 mg dose of torsemide and the 40 mg dose of furosemide, body weight decreased significantly relative to baseline, and total and fractional 24-hour urinary excretion of sodium, chloride, and potassium and urine volume increased significantly. The 10 mg torsemide dose also produced a significant increase in urine volume. The results indicate that intravenous torsemide is effective for the acute treatment of sodium and fluid retention resulting from moderate to severe congestive heart failure.

Correlation between fructose 2,6-bisphosphate and lactate production in skeletal muscle

The epinephrine-induced production of lactate in nonexercising muscles may be due in part to allosteric activation of 6-phosphofructo-1-kinase by fructose 2,6-bisphosphate (F-2,6-P2). To determine if a correlation exists between F-2,6-P2 and lactate production in skeletal muscle, isolated rat hindlimbs were perfused for 30 min with a medium containing epinephrine at concentrations varying between 1.7 +/- 0.5 and 72.4 +/- 4.2 nM. In comparison to control values, hindlimbs perfused with 72.4 +/- 4.2 nM epinephrine had a two- to threefold increase in F-2,6-P2 and a fourfold increase in muscle lactate production. Hindlimb lactate production was highly correlated to gastrocnemius adenosine 3',5'-cyclic monophosphate (r = 0.80), fructose 6-phosphate (r = 0.87), and F-2,6-P2 (r = 0.81). The adenosine 3',5'-cyclic monophosphate-mediated increase in glycogenolysis with consequent increase in fructose 6-phosphate (substrate for 6-phosphofructo-1-kinase and 6-phosphofructo-2-kinase) is likely important for induction of lactate production by inactive muscle. The high correlation between muscle F-2,6-P2 and muscle lactate production at varying concentrations of epinephrine supports the hypothesis that the epinephrine-induced activation of glycolysis and lactate production in nonexercising muscle is mediated in part by increases in F-2,6-P2 levels.