Modulation of pacemaker activity in sheep cardiac Purkinje fibers by stimulation of β-adrenoceptor subtypes

The electrophysiological effects mediated by ₁- and ₂- in spontaneously active sheep cardiac Purkinje fibers were investigated using the non-selective agonist (–)-isoproterenol (IPN) and the selective agonists (–)-noradrenaline (₁) and procaterol (₂) in the absence and presence of the selective antagonists bisoprolol (₁) and ICI 118,551 (₂).IPN (0.01 mol/l) increased the spontaneous rate by 54% and the slope of diastolic depolarization by 68% of the respective control values. Further, IPN increased the action potential duration at –20 mV (APD –20 mV) from 96 to 154 ms, reduced the APD –70 mV by 17% and the duration of the diastole by 39% and slightly hyperpolarized the maximum diastolic potential. These effects were partially inhibited by ICI 118,551 (0.03 mol/l), diminished by bisoprolol (0.1 mol/l) and almost completely blocked by the combination of both antagonists. Concentration response curves of IPN were influenced by the selective antagonists as follows: ICI 118,551 (0.03 mol/l) shifted the curves to the right by 0.2–0.4 log units and increased the slope factor. Bisoprolol (0.1 mol/l) induced a greater shift to the right by 1.1–1.5 log units. Combination of bisoprolol with ICI 118,551 shifted the curves to the right by 1.5–1.7 log units.Noradrenaline (0.3 mol/l) elicited similar actions as IPN. Bisoprolol (0.1 mol/l) shifted the concentration response curves of noradrenaline to the right by 1.1–1.9 log units. Actions of procaterol (0.1 mol/l) were weak, attained only 15–35% of the maximal effects of IPN and could be blocked by ICI 118,551 (0.03 mol/l).These results show that the increase of pacemaker activity induced by catecholamines in sheep cardiac Purkinje fibers is predominantly mediated by stimulation of ₁. However, contribution of ₂ mediated effects could be demonstrated.Supported by Ministerium für Wissenschaft und Forschung, Nordrhein-Westfalen, Projekt-Nr, 40008786.     

Granulocyte elastase in assessment of severity of acute pancreatitis

Complexes of granulocyte elastase and ₁-antitrypsin are markers for granulocyte activation. In 75 patients with acute pancreatitis these complexes were immunologically determined daily in plasma during the first week of hospitalization. Patients were classified into three groups: mild pancreatitis (I, 1 complication, N=34), severe pancreatitis (II, 2 complications, N= 29), lethal outcome (III, N=12). Initially, granulocyte elastase (mean±sem) was lower in group I (348±39 g/liter) as compared to groups II (897±183 g/l) and III (799±244 g/liter), P<0.001 for I vs II + III. Initial elastase concentrations >400 g/liter were consistent with a severe or fatal course of the disease but did not distinguish between severe and lethal pancreatitis. In patients with mild or severe disease, mean elastase concentrations decreased continuously during the following days (197±15 g/liter in mild cases, 325±30 g/liter in severe cases at day 7). In patients with lethal disease, however, mean elastase concentrations even increased at day 2 and remained higher than 700 g/liter during the observation period. At days 1 and 2 the predictive value for severe or lethal disease of raised (>400 g/liter) elastase concentrations [positive predictive value (PPV) 82%, negative predictive value (NPV) 81%] was better than that of elevated (>100 mg/liter) C-reactive protein (PPV 73%, NPV 73%), elevated (>4.0 g/liter) ₁-antitrypsin (PPV 59%, NPV 50%), or decreased (<1.5 g/liter) ₂-macroglobulin (PPV 82%, NPV 67%). When the time course of the concentrations of the acute-phase proteins was studied, it was found that rises of granulocyte elastase were followed by elevated C-reactive protein levels after one day, by elevated ₁-antitrypsin levels after two days and by decreased ₂-macroglobulin levels after three to four days. We conclude that granulocyte elastase is a good early marker for the severity of acute pancreatitis. Compared with elevated levels of C-reactive protein and ₁-antitrypsin release of granulocyte elastase reflects an event that precedes acute-phase protein induction.     

Pharmacological evidence for beta3 adrenoceptors in the control of rat gastric acid secretion

The effect of the ₃-adrenoceptor agonist BRL37344 on gastric acid secretion evoked by different secretory stimuli was investigated in anaesthetized rats with lumen-perfused stomachs in comparison with the ₂-adrenoceptor agonist clenbuterol. Intravenous injections of BRL37344 (1–10 mol/kg) and clenbuterol (0.01–1 mol/kg) dose-dependently reduced 2-deoxy-D-glucose-induced acid secretion, with BRL37344 about forty times less potent than clenbuterol. BRL37344 (0.1–3 mol/kg) inhibited pentagastrin-induced acid output, whereas clenbuterol was effective only at high doses (10–100 mol/kg). The inhibitory effect of BRL37344 on pentagastrin-induced acid secretion was not modified by the nonselective –adrenoceptor antagonist propranolol, but it was prevented by bupranolol, a ₃-adrenoceptor antagonist. Furthermore, neither BRL37344 (10 mol/kg) nor clenbuterol (100 mol/kg) modified the acid secretion induced by histamine. These data suggest that ₃ adrenoceptors have an inhibitory role in the control of rat gastric acid secretion induced by indirect stimuli.     

B cell adrenoceptors and sulphonylurea-induced insulin release in mouse islets

Summary Interactions of tolbutamide and glibenclamide with B cell adrenoceptors have been reported. This study evaluated the possible role of such interactions in the stimulation of insulin release. Mouse islets were incubated in the presence of 10 mmol/l glucose alone or with tolbutamide (10 mol/l) or glibenclamide (0.02 mol/l). At 0.01–10 mol/l, blockers of ₂-adrenoceptors (yohimbine, idazoxan) or ₁-adrenoceptors (prazosin) had practically no effect on glucose-induced insulin release and did not affect its potentiation by sulphonylureas, except for a slight increase by 10 mol/l prazosin and idazoxan. Nonspecific -blockers (phentolamine, dihydroergotamine) increased control release at 10 mol/l, but only the latter amplified the response to tolbutamide. Blockers of -adrenoceptors were tested at 0.1–100 mol/l: propranolol (₁, ₂), metoprolol (₁) and compound ICI 118-551 (₂). They increased glucose-induced insulin release at 100 mol/l but variably altered the effect of sulphonylureas. Blockers of adrenoceptors have, thus, no effect on insulin release in vitro at therapeutic concentrations. At high concentrations, they non-specifically affect the action of sulphonylureas. We conclude that an interaction with B cell adrenoceptors is not involved in the insulinotropic action of sulphonylureas.     

Role of Central Interleukin-1β in Gastrointestinal Motor Disturbances Induced by Lipopolysaccharide in Sheep

Cytokines are involved in the symptoms of theacute phase response induced by infectious diseases inhumans as well as in animals, and interleukin-1(IL-1 ) has a pivotal role in these changes. The role of central IL-1 in the gastrointestinalhypomotility and fever evoked by intravenousadministration of lipopolysaccharide (LPS) and themechanisms involved, were investigated in sheep as anexperimental model. LPS (0.1 g/kg, intravenously)induced gastrointestinal hypomotility and fever thatwere significantly reduced by priorintracerebroventricular administration of IL-1receptor antagonist protein (IL-1ra, 2 g/kg). The effects of LPS were mimickedby intracerebroventricular IL-1 (50 ng/kg),whereas IL-1 injected intravenously at the samedose only caused a slight and transient fever withoutmodifying the gastrointestinal motility. Priorintracerebroventricular administration of thecyclooxygenase inhibitor indomethacin (100 g/kg) butnot the corticotropin-releasing factor (CRF) receptorantagonist -helical CRF_9-41 (5 g/kg) blocked alleffects evoked by both LPS and IL-1. These resultssuggest that in sheep, LPS induces digestive motordisturbances through a central release of IL-1 andprostaglandins.     

Distribution of β-Adrenoceptor Subtypes in Gastrointestinal Tract of Nondiabetic and Diabetic BB Rats A Longitudinal Study

The effects of aging and diabetes on thedistribution of -adrenoceptor subtypes in the gutwere investigated in the BB rat.[¹²⁵I]Cyanopindolol binding to 10-msections was evaluated using film autoradiography. Cyanopindolol binding to -,₁-, and₂-adrenoceptors was displaced by 1M propranolol, 50 nM ICI-89-406, and 100 nMICI-118-551, respectively. -Adrenoceptor bindingwas highest in the circular muscle of proximal colon and lowest in thepylorus of 4- to 5-month-old rats. Aging (8- to10-month-old vs. 4- to 5-month-old rats) was associatedwith increased -adrenoceptor binding in thepylorus and reduced binding in the proximal colon.Diabetes had a time-dependent effect on the level of-adrenoceptor binding. It was increased in theantral and pyloric stomach but longer periods ofdiabetes caused a reduction in -adrenoceptorbinding in the pylorus. Those in the intestine werereduced time-dependently and involved₁- or ₂-adrenoceptorsor both.     

Triplication (/ααα<Superscript>Anti3.7</Superscript>) or deletion (-α<Superscript>3.7</Superscript>/) association in Argentinian β-thalassemic carriers

Prevalence of alpha gene triplication or deletion in -thalassemia carriers was studied in 109 unrelated individuals in Rosario, Argentina. In different populations -^3.7 allele presents a higher prevalence than ^anti3.7; thus, -thalassemia associated with -thalassemia is more frequently observed. Nevertheless, this event was detected in only one case (0.9%), while the association with alpha triplication was present in two subjects (1.8%).     

Synergistic interactions between interferonβ and carboplatin on SK-MEL 28 human melanoma cell growth inhibition in vitro

Carboplatin and interferon (IFN ) were tested alone and in combination for their anti-proliferative activity on the human melanoma cell line SK-MEL 28 in vitro. Cells were incubated for 4 days in the presence of carboplatin (0.1 mM and 0.1 M) and interferon (5 pM and 5 nM) and cell growth inhibition was determined by the sulphorhodamin B assay. The antiproliferative effects of the drug combinations were analysed using Berenbaum's hyperplane theorem to determine additive, synergistic and antagonistic effects. IFN was found to be 10 000 times more active in inhibiting cell growth of SK-MEL 28 cells than carboplatin on the basis of IC₅₀ values (IFN: IC₅₀=1.24 nM, carboplatin: IC₅₀=18.2, M). The addition of IFN at 0.5 nM reduced the IC₅₀ value of carboplatin 18.0-fold; with IFN at 0.05 nM a dose reduction of 1.84 was measured. At the carboplatin: IFN molar concentration ratios of 2000:1 and 6000:1, interaction indices (I) of 0.66 and 0.83 were determined respectively, indicating synergistic interactions between the two drugs. At higher carboplatin: IFN molar ratios (20 000:1 and 60 000:1) an additive interaction was observed (I=1.07 and 1.20). However, further in vitro studies with serveral melanoma cell lines are necessary to evaluate the potential effectiveness of the drug combination of carboplatin and IFN for eventual clinical utilisation.     

Acute and chronic treatment with glucocorticosteroids,modifying the β2-adrenergic response of the guinea pig trachea

The effect of R2-adrenoceptor agonists on airway smooth muscle relaxation may be subject to desensitization. It could be modified by glucocorticosteroid treatment. An increase in the R2 agonist response by gluco corticosteroids in vitro has been described. We studied the effects of acute and chronic treatment with dexamethasone on the relaxation response of tracheal smooth muscle to R2 agonists, fenoterol and salbutamol. Fenoterol showed a greater force of relaxation than salbutamol, and both drugs induced desensitization. Acute treatment with dexamethasone reduced desensitization to both ₂ agonists. Chronic treatment (120 g/kg of dexamethasone for 7 days) reduced the desensitization to fenoterol alone. Dexamethasone (200 g/kg for 7 days) increased relaxation to salbutamol and reduced desensitization to both drugs. The interaction between ₂ agonists and glucocorticosteroids could be important in the clinical use of both drugs in the treatment of asthma.Offprint requests to: G. Manso     

Synovial fluid nitric oxide levels in patients with knee osteoarthritis

Nitric oxide (NO) has an important role in the inflammatory arthropathies. This study investigated NO levels in the synovial fluid and plasma of patients with primary osteoarthritis (OA) of the knee. Twenty-seven cases with primary knee OA and 13 controls were recruited for the study. Nitrate/nitrite levels of synovial fluid and plasma were measured by Griess reaction, and interleukin-1 (IL-1) levels were measured quantitatively by a sandwich immunoassay technique. We found a significant increase in the synovial fluid nitrate/nitrite levels in cases with primary OA of the knee compared to controls (50.26±23.63 g/l vs 32.49±10.05 g/l, p=0.002) as well as increased plasma nitrate/nitrite levels (57.06±23.32 g/l vs 39.98±16.36 g/l, p=0.012). There was no difference in plasma and synovial fluid IL-1 concentrations between the study and control groups. These results may be considered as supporting evidence that NO might be one of the factors responsible for cartilage destruction in primary osteoarthritis of the knee.Abbreviations NO Nitric oxide - OA Osteoarthritis - TMJ Temporomandibular joint     

Effects of Voltage-Sensitive Calcium Channel Blockers on Extracellular Dopamine Levels in Rat Striatum

Various subtypes of voltage-sensitive calcium channels (VSCCs) support the release of dopamine (DA) in the central nervous system. Using in vivo microdialysis, we investigate the influence of these subtypes of calcium channels on dopaminergic terminals in the rat striatum. L-type (nifedipine-sensitive), N-type (-conotoxin GVIA-sensitive), or N- and P/Q-type (-conotoxin MVIIC-sensitive) Ca²⁺ channels were blocked using selective antagonists injected locally, and K⁺-evoked DA release was measured in freely moving animals. K⁺(100 mM) induced a massive increase of basal DA extracellular levels (930%) and was without significant effect on extracellular levels of DA metabolites DOPAC and HVA, and on the serotonin metabolite 5HIAA. -Conotoxin GVIA (1 M) and -conotoxin MVIIC (1 M) significantly reduced the K⁺-evoked DA release by 55 and 62%, respectively. The simultaneous application of the two conotoxins at the same concentration reduced K⁺-evoked DA release by 66%. Nifedipine (10 M) had no significant effect on K⁺-evoked DA release, while neomycin, a nonspecific VSCC blocker, produced a highly significant decrease when applied at 250 and 500 M (56 and 75%, respectively). The compounds, however, had no effect on basal DA release and on the levels of extracellular DOPAC, HVA, and 5HIAA. These results suggest that under high and persistent conditions of membrane depolarization (15 min, 100 mM K⁺), striatal DA release is mainly mediated by N-type VSCCs.     

α2-Adrenergic stimulation counteracts glucose-induced rise of sodium in pancreatic islets exposed to ouabain

The effects of ₂-adrenergenic activation by clonidine on sodium handling were analysed in beta-cell-rich pancreatic mouse islets. In the steady-state situation, clonidine (1 M) amplified lowering of sodium induced by 20 mM glucose, while the content remained unchanged in 3 mM glucose. The loss of sodium in Na⁺-deficient medium was stimulated by glucose but was not affected by clonidine. This agonist also did not influence the ouabain-induced uptake of sodium at 3 mM glucose but partially counteracted additional uptake in response to 20 mM glucose. Although lacking effects of its own, 5 M yohimbine completely counteracted the action of clonidine. The glucose amplification of the ouabain-induced uptake of sodium was suppressed also by 10 M of the Ca²⁺-channel blockers methoxyverapamil and diltiazem. Both tolbutamide (100 M) and dibutyryl cyclic AMP (1 mM) mimicked the action of glucose by promoting clonidine-sensitive uptake of sodium in the presence of ouabain. It is concluded that activation of ₂-adrenoceptors has profound effects on the sodium handling of pancreatic beta-cells exposed to glucose and other stimulators of insulin release.     

Alterations in the heart sarcolemmal Ca2+ transport activity by some β-adrenergic antagonists

Summary The effects of some -adrenergic antagonists such as acebutolol, propranolol, pindolol and oxprenolol (1–1000 M) were studied on the rat heart sarcolemmal Ca²⁺ transport activities. Pindolol enhanced sarcolemmal ATP-dependent Ca²⁺ binding and Ca²⁺-stimulated ATPase whereas acebutolol had no effect. Both propranolol and oxprenolol had biphasic actions on the sarcolemmal Ca²⁺ pump activities; the lower concentrations (1 and 10 M) were stimulatory, but the higher concentrations (100 and 1000 M) were inhibitory. None of the drugs used in this study had any effect on Mg²⁺ ATPase and non-specific Ca²⁺ binding activities of heart sarcolemma except that 1000 M propranolol decreased Mg²⁺ ATPase activity significantly. Mitochondrial and microsomal ATP-dependent Ca²⁺ binding activities were unaffected by these drugs (1–1000 M), except that 1000 M propranolol was inhibitory. These results suggest differences among various -adrenergic blocking drugs with respect to their actions on sarcolemmal Ca²⁺ pump in the myocardium.     

17β-Estradiol Attenuates Quinolinic Acid Insult in the Rat Hippocampus

A number of studies have shown that 17-estradiol has neuroprotective properties. In this study the neuroprotective effect of 17-estradiol against quinolinic-acid-induced neuronal damage was investigated. Ovariectomized rats were separated into three groups of five animals each. Rats received daily subcutaneous injections of either olive oil or 17-estradiol in olive oil for 7 days prior to and following a single intrahippocampal injection of 1 mol quinolinic acid in 2 L phosphate-buffered saline. The brains were removed and the hippocampi either sectioned and stained for microscopic examination or used in glutamate receptor saturation binding studies. Glutamate receptor displacement binding studies were also performed using concentrations of 0.05 nM–5 M 17-estradiol or quinolinic acid. The results show that 17-estradiol protects hippocampal neurons from quinolinic-acid-induced neurodegeneration by competing with quinolinic acid to bind to the N-methyl-D-aspartate (NMDA) receptor. This would result in a decrease in intracellular free-calcium influx and resultant neuronal swelling.     

Determination of human ketone body kinetics using stable-isotope labelled tracers

Summary In order to avoid the use of radioactive tracers for the determination of human ketone body turnover, we have developed a method using a primed-continuous infusion of ¹³C-labelled acetoacetate or D--hydroxybutyrate. Determination of the mole percent enrichment of blood acetoacetate and D--hydroxybutyrate was performed by gas chromatography/mass spectrometry. In the post-absorptive state, the mean total ketone body appearance rate, determined in four subjects, was 3.74 mol · kg^–1 · min^–1 using [3,4-13 C2] acetoacetate and 2.76 mol · kg^–1 · min^–1 using [3-¹³C]D--hydroxybutyrate, values in agreement with those reported in studies with ¹⁴C-labelled tracers. In order to evaluate the usefulness of the method for determination of ketone body kinetics in non steady-state conditions, we infused four subjects with natural sodium acetoacetate and calculated the isotopically determined total ketone body appearance rate using a single compartment model (volume of distribution 0.201/kg; functional pool fraction: 1). During the tests with [3,4-¹³C2]-acetoacetate, the actual infusion rates of natural acetoacetate were 7.3±0.3, 14.6±0.8, 21.9±1.2 and 10.9 ± 0.6 mol · kg^–1 · min^–1 whereas the corresponding isotopically determined total ketone body appearance rates were respectively 9.2±1.0, 16.3±0.7, 23.1±1.1 and 10.7±0.8 mol· kg^–1 · min^–1. During the tests with [3-¹³C]D--hydroxybutyrate, the actual infusion rates were 8.4 ± 0.5, 16.8 ± 0.9, 25.2 ±1.4 and 12.6±0.8 mol · kg^–1 · min^–1, and the isotopically determined appearance rates respectively 11.1±0.7, 16.7±0.7, 25.0±1.1 and 11.1 ± 0.7 mol · kg^–1 · min^–1. Thus, using either tracer we found a good agreement between acetoacetate infusion rate and tracer-determined appearance rate of ketone bodies. In conclusion, the present method may be used to determine human ketone body kinetics under steady-state and non steady-state conditions.     

Down-regulated β-adrenoceptors in severely failing human ventricles: Uniform regional distribution,but no increased internalization

Summary In chronic heart failure cardiac -adrenoceptors are decreased. In this study we investigated whether a) in severely failing human ventricles -adrenoceptors are uniformly decreased or regional variations exist, and b) the -adrenoceptor decrease is caused by increased internalization or is a real loss in -adrenoceptors. For this purpose we assessed -adrenoceptor number and subtype distribution in a particulate fraction (mainly sarcolemmal plasma membranes) and a light vesicle fraction of right and left ventricular segments (obtained by cutting transversal, rings of 2 cm from the midventricular regions) of explanted hearts from 2 patients with end-stage congestive dilated cardiomyopathy (DCM) and one patient with end-stage ischemic cardiomyopathy (ICM). In all three hearts ventricular -adrenoceptor number was very low (7.5–10 and 21–26 fmol/mg protein in DCM, 15–22 fmol/mg protein in ICM compared to 68–74 fmol/mg protein in non-failing ventricles). -Adrenoceptors were uniformly decreased over the whole ventricular region and no considerable regional variations existed. The same held true for ₁- and ₂-adrenoceptors. In ICM decrease in -adrenoceptors was due to a concomitant reduction in ₁- and ₂-adrenoceptors, in DCM it was mainly caused by ₁-adrenoceptor down-regulation. In all ventricular segments investigated light vesicle -adrenoceptors amounted to about 5–7% of total ventricular -adrenoceptors and this was not significantly different from non-failing left ventricles. We conclude that a) in severely failing human ventricles -adrenoceptors are evenly down-regulated and no regional variations exist and b) the decrease in -adrenoceptors is not due to enhanced internalization but is a real loss of -adrenoceptors.Abbreviations DCM dillted cardiomyopathy - ICM ischemic cardiomyopathy - ICI 118,551 erythro-(±)-1-(7-methylindan-4-yloxy)-3-isopropylaminobutan-2-ol hydrochloride - CGP 12177 (±)-4-(3-tertiarybutylamino-2-hydroxypropoxy)-benzimidazole-2-on hydrochloride - ICYP (–) [¹²⁵I]-Iodocyanopindolol     

Detection of anti-bovine β2-glycoprotein I antibody in sera from patients with antiphospholipid syndrome

We studied and characterized anti-bovine ₂ I antibodies (aB₂-GPI) in sera from patients with antiphospholipid syndrome (APS) by ELISA. Bovine ₂-glycoprotein I ₂-GPI was purified by heparin affinity and DEAE ion-exchange chromatography, and identified on immunoblots using a monoclonal antibody against human ₂-GPI and by amino acid sequence analysis. aB₂-GPI levels in the sera from 36 APS patients were measured by ELISA using purified bovine ₂-GPI as an antigen. The mean±standard deviation level of aB₂-GPI was 17.4±22.0 units in the 58% of APS patients who were positive. There was a significant correlation (P=0.003) between aB₂-GPI and anticardiolipin antibody (aCL) levels. aB₂-GPI from the sera of patients with APS was inhibited by bovine ₂-GPI itself. Purified IgG from the sera of patients with APS showed that bovine ₂-GPI was capable of acting as a cofactor for aCL. Purified bovine ₂-GPI was useful antigen for conventional ELISA. aB₂-GPI may contribute to the further development of aCL analysis and to the understanding of the pathogenesis of APS.     

Investigations on metabolism,genotoxic effects and carcinogenicity of 2,2′-dichlorodiethylether

Summary Either 40 mole or 160 mole 2,2-DDE was injected into male Wistar rats and the metabolites, TdGA and HEMA, were determined in the 24-h urine specimens. Comparative investigations were carried out giving equimolar amounts of chloroethanol and 2-chloroacetaldehyde diethyl acetal. In a further step, inhalation experiments were performed to determine urinary excretion of the two metabolites after an 8-h exposure of male Wistar rats to 10, 50, 100, and 500 ppm 2,2-DDE and to 50, 200, und 1000 ppm vinyl chloride.A long-term study was conducted to investigate the possible carcinogenicity of 2,2-DDE in male and female Sprague-Dawley rats following s.c. injections of 4.36 mole and 13.1 mole 2,2-DDE in DMSO per week. The evaluation of tumor development in treated groups and controls were based on macroscopic inspection and histological examinations of the suspect organs and tissues.Analysis of the metabolites showed that HEMA excretion was much lower than the excretion of TdGA following the uptake of 2,2-DDE, 2-chloroethanol and 2-chloroacetaldehyde diethyl acetal. Contrary to these, vinyl chloride uptake resulted in a higher urinary excretion of HEMA than TdGA.There was no appreciable increase in the number of tumors detected in 2,2-DDE-treated animals when compared with untreated or DMSO-treated groups.Since irradiation of 2,2-DDE with UV did not elevate mutagenic activity of the compound against Salmonella typhimurium TA100, the high mutagenicity of the compound found in a desiccator cannot be due to the liberation of mutagenic compounds produced under the influence of UV light.Abbreviations 2,2-DDE 2,2-dichlorodiethylether - DMSO dimethylsulfoxide - HEMA hydroxyethyl mercapturic acid - TdGA thiodiglycolic acid     

The effects of parabiosis on serum and kidney glycosidase activities in spontaneously diabetic mice

Summary Spontaneously diabetic non-obese mice of the ICR strain were newly inbred in Shionogi laboratory, Japan. Animals became diabetic suddenly, more frequently and severely in females. Blood glucose levels were 452±73 mg/100 ml with serum insulin levels of < 1.0 U/ml in the fed state. Parabiosis with normal control ICR mice for 2 weeks decreased the blood glucose level to 260±51 mg/ 100ml (P<0.01) and resulted in serum insulin levels of 46.0±18.0 U/ml (P<0.01). Kidney homogenate -N-acetylglucosaminidase and -galactosidase activities were reduced in diabetic mice (42% and 44% decrease respectively) (P<0.025 and P<0.001), and restored almost to normal after 2 weeks of parabiosis. Renal -mannosidase activity was decreased 43% (P<0.001) in the diabetic mice but unaffected by parabiosis. Serum -N-acetylglucosaminidase, -galactosidase and -glucosidase activities were significantly increased in diabetic mice (179%; 233% and 58% increase respectively) (P<0.005, P<0.001 and P<0.001), and returned to normal with parabiosis.     

Deleterious effects of digitalis on reperfusion-induced arrhythmias and myocardial injury in ischemic rat hearts: possible involvements of myocardial Na+ and Ca2+ imbalance

Summary Isolated rat hearts were made ischemic for 25 min after an initial recirculating perfusion, followed by 30 min of reperfusion. In some hearts, interventions including administration of ouabain and/or high [K⁺] in the buffer were performed during the first 10 min of reperfusion.During ischemia, intracellular Na⁺ (Na_i) increased from 15 to 64 [mol/g dry weight (dwt). During reperfusion, Na_i declined rapidly (at 10 min of reperfusion: 48 nol/g dwt, at 30 min: 25 mol/g dwt) and regular rhythm was recovered within 10 min in hearts without any intervention during reperfusion.⁴⁵Ca²⁺ uptake increased from 0.8 to 7.5 mol/g dwt after 30 min of reperfusion. Ventricular function recovered by 45 %.A 10-min perfusion with 10 or 50 M of ouabain increased Na_i (17 to 21 or 27 mol/g dwt) with increased left-ventricular (LV) contractile function, but these effects were reversed by combination of high perfusate [K⁺] (20 mM) in non-ischemic hearts.A 10-min reperfusion with ouabain retarded or stopped the decline in Na_i (at 10 min of reperfusion: 54 or 63 mol/g dwt, at 30 min: 32 or 40 mol/g dwt). These amounts of ouabain also increased the incidence of ventricular tachyarrhythmias during reperfusion to 30 % or 50 %, and increased the duration of ventricular fibrillation from 6.5 to 11.5 or 18.0 min.⁴⁵Ca²⁺ uptake reached to 8.8 or 10.0 mol/g dwt, and function recovered only 35 % or 28 %. When high perfusate [K⁺] was combined with ouabain during reperfusion, the retarded decline in Nai, augmented⁴⁵Ca²⁺ uptake, and reduced recovery of function caused by ouabain alone were attenuated. These results suggest that digitalis has toxic effects on reperfused ischemic hearts by inhibition of rapid active outward transport of previously elevated Na_i and potentiation of Ca²⁺ overload.The work was supported in part by grant HL 37936 from the National Heart, Lung and Blood Institute. J. R. Neely was deceased on November 29, 1988