Acute effects of metabolic hormones in swine

Many metabolic hormones (glucagon, hydrocortisone, corticosterone, TSH, thyroxine and triiodothyronine) did not stimulate porcine adipose tissue lipolysis in vitro. Growth hormone and ACTH stimulated lipolysis at high concentrations, in the presence of theophylline. Insulin inhibited lipolysis. Infusion of metabolic hormones with measurement of plasma free fatty acid and glycerol concentrations, purportedly indicative of in vivo lipolysis, indicated that glucagon and somatotropin had no effect, adrenocorticotropin increased and insulin depressed plasma concentrations of the metabolites. Overall, the in vitro predicts the in vivo response. There were exceptions, e.g. adrenocorticotropin moderately increased plasma metabolites but had little effect in vitro.     

Acute and chronic effects of bupivacaine on muscle energetics during contraction in vivo: a modular metabolic control analysis

Bupivacaine is a widely used anaesthetic injected locally in clinical practice for short-term neurotransmission blockade. However, persistent side effects on mitochondrial integrity have been demonstrated in muscle parts surrounding the injection site. We use the precise language of metabolic control analysis in the present study to describe in vivo consequences of bupivacaine injection on muscle energetics during contraction. We define a model system of muscle energy metabolism in rats with a sciatic nerve catheter that consists of two modules of reactions, ATP/PCr (phosphocreatine) supply and ATP/PCr demand, linked by the common intermediate PCr detected in vivo by (31)P-MRS (magnetic resonance spectroscopy). Measured system variables were [PCr] (intermediate) and contraction (flux). We first applied regulation analysis to quantify acute effects of bupivacaine. After bupivacaine injection, contraction decreased by 15.7% and, concomitantly, [PCr] increased by 11.2%. The regulation analysis quantified that demand was in fact directly inhibited by bupivacaine (-21.3%), causing an increase in PCr. This increase in PCr indirectly reduced mitochondrial activity (-22.4%). Globally, the decrease in contractions was almost fully explained by inhibition of demand (-17.0%) without significant effect through energy supply. Finally we applied elasticity analysis to quantify chronic effects of bupivacaine iterative injections. The absence of a difference in elasticities obtained in treated rats when compared with healthy control rats clearly shows the absence of dysfunction in energetic control of muscle contraction energetics. The present study constitutes the first and direct evidence that bupivacaine myotoxicity is compromised by other factors during contraction in vivo, and illustrates the interest of modular approaches to appreciate simple rules governing bioenergetic systems when affected by drugs.     

Cell cycle-dependent effects of wortmannin on radiation survival and mutation

Wortmannin, a known radiation sensitizer, has been used in experiments with synchronized cells to compare its effect on radiation survival and mutation induction within the cell cycle. PL61 cells (CHO cells with an inactivated HPRT gene containing a single active copy of a bacterial gpt gene) were synchronized by mitotic selection. Wortmannin administered before gamma irradiation caused a greater sensitization in G(1)-phase cells relative to late S/G(2)-phase cells. Preferential radiosensitization of G(1)-phase cells by wortmannin sets a limit to the proposed use of wortmannin in radiation therapy, since, in contrast to normal tissues, tumors usually have high proportions of S-phase cells. Wortmannin increased mutation frequencies in both G(1)- and S/G(2)-phase cells. Interestingly, relative increases in radiation-induced mutations in G(1) and S/G(2) phases were comparable. The results are discussed in terms of the contributions of different repair modes in the production of mutations.     

Acute metabolic effects of ammonia in mouse brain

Acute effects of intraperitoneal administration of ammonium chloride (200 mg/kg) on Na⁺,K⁺-ATPase and amino acid content of the glutamate family (glutamate, aspartate, alanine, glutamine, and GABA), as well as the enzymes involved in the metabolism of these amino acids, have been studied in the different regions of brain and liver in mice. A significant increase in the activity of Na⁺,K⁺-ATPase was observed in the cerebellum, cerebral cortex, and brain stem. A similar increase in the activity of glutamate dehydrogenase was observed in the brain stem, while a moderate increase in the activity of this enzyme was observed in the cerebral cortex and liver in the mice treated with ammonium chloride. In all three regions of brain, a 50% decrease was observed in the activity of alanine aminotransferase, while the activity of aspartate aminotransferase significantly rose in the brain stem. The activity of glutamine synthetase did not change much in the three regions of brain, and a significant fall was registered in the liver. The activity of tyrosine aminotransferase showed a rise in the cerebellum, brain stem, and in liver. Not much change was observed in the protein content in either brain or liver, whereas there was a 1.5-fold increase in the total RNA content in the liver of the animals treated with ammonium chloride. Under the experimental conditions, there was an increase only in the content of glutamine, of all the amino acids tested, in the cerebral cortex and liver. Similar results were obtained with homogenates of tissues enriched with ammonium chloride (in vitro) for the enzyme systems studied. These results are discussed, and the probable metabolic and functional significance of ammonia in brain is indicated.     

The hemodynamic and metabolic effects of 2-deoxy-D-glucose in waking Wistar rats]

The effect of 2-deoxy-D-glucose (2-DG) in a dose of 250 mg/kg as a stressogenic factor on changes in hemodynamic parameters and metabolism in awake rats was quantified during 6 hours. It was found that a single 2-DG injection causes lowering of blood pressure on min 40 and 120. Heart rate tended to slow down. Diminished glucose concentration in the brain observed on experiment minute 15 induced a number of adaptive reactions in the body. Epinephrine plasma levels increased sharply on min 15 and 40. Norepinephrine concentrations elevated slightly only at the beginning of the experiment. The maximal glucose level in blood plasma was observed on min 40 and 120 and that of lactate 40 min following 2-DG injection. The level of immunoreactive insulin rose. Glucose content in the heart came up sharply on min 15 and 40. Lactate concentration in the heart increased continuously.     

Acute effects of adrenaline on platelet aggregation and kinetics in vivo

The platelet (Plt) contribution to cardiovascular events triggered by adrenergic stress is supported by some experimental and necropsy data, but a cause and effect link and mechanism have not yet been clearly demonstrated. Adrenergic stress was simulated by three successive adrenaline (A) injections (80 micrograms/kg) in anesthetized dogs previously infused with indium111 labelled Plt (111In-Plt) for a gamma-camera study. Adrenaline induced an acute and significant decrease in the Plt aggregation ratio (PAR) and a parallel decrease in the Plt count as well as in the circulating 111In-Plt, mirroring a significant and persistent Plt sequestration mainly in the liver and spleen. The long-lasting and significant decrease in the circulating Plt count observed 15 min after each A injection can be explained by a persistent retention of Plt. Further studies are in progress in order to disclose if this corresponds to platelet microaggregate embolization in microvessels of the organs so far analysed. If this postulate can be confirmed the hypothesis of an adrenergic stress triggering of ischemic events will be justified.     

Effects of dihydroergotamine on hemodynamic molsidomine actions in anesthetized dogs

In pentobarbital-anesthetized mongrel dogs the intravenous actions of 0.50 mg/kg molsidomine on pulmonary artery and left ventricular (LV) end-diastolic pressures and internal heart dimensions (preload), left ventricular systolic and peripheral blood pressures, and total peripheral resistance (afterload), as well as on heart rate, dP/dt, stroke volume, and cardiac output (heart performance) were studied for 2 h. Hemodynamic molsidomine effects were influenced by increasing amounts of intravenously infused dihydroergotamine solution (DHE, 1-64 micrograms X kg-1 X min-1). Molsidomine decreased preload, stroke volume, and cardiac output for over 2 h but decreased ventricular and peripheral pressures for 45 min. Systemic vascular resistance showed a tendency to decrease while heart rate and LV dP/dtmax were not altered. DHE infusion reversed molsidomine effects on the preload and afterload of the heart. The diminished stroke volume was elevated so that cardiac output also increased. Total peripheral resistance increased while heart rate fell in a dose-dependent fashion. The LV dP/dtmax remained unchanged until the highest dose of 64 micrograms X kg-1 X min-1 DHE elevated the isovolumic myocardial contractility. These experiments indicate that DHE can reverse the intravenous molsidomine effects on hemodynamics. Most likely, this is mediated through peripheral vasoconstriction of venous capacitance vessels, thereby affecting molsidomine's action on postcapillary beds of the circulation.     

Acute metabolic effects of taurine on the enzymes metabolizing glutamate and gaba

100 mg of taurine per kg body weight had been administered intraperitoneally and 30 min after the administration the animals were sacrificed. Glutamate dehydrogenase, aspartate aminotransferase, alanine aminotransferase, glutaminase, glutamine synthetase, glutamate decarboxylase and GABA aminotransferase along with the content of glutamate and GABA in cerebral cortex, cerebellum and brain stem were studied and compared with the same obtained in the rats treated with normal saline in place of taurine. The results indicated a significant decrease in the activity of glutamate dehydrogenase in cerebral cortex and cerebellum and a significant increase in brain stem. Glutaminase and glutamine synthetase were found to increase significantly both in cerebral cortex and cerebellum. The activities of glutamate decarboxylase was found to increase in all the three regions along with a significant decrease in GABA aminotransferase while the content of glutamate showed a decrease in all the three brain regions, the content of GABA was observed to increase significantly. The above effects of taurine on the metabolism of glutamate and GABA are discussed in relation to the functional role of GABA and glutamate. The results indicate that taurine administration would result in a state of inhibition in brain.     

Acute effects of alpha-MSH on the rat zona glomerulosa in vivo

alpha-MSH acutely enhanced the plasma concentration of aldosterone (but not that of corticosterone) in the rat, with a maximal response at a dose of 100 micrograms/kg. This dose of alpha-MSH increased the blood level o aldosterone and the activity of 11 beta-hydroxylase and 18-hydroxylase of capsular adrenals in rats infused for 24 h with dexamethasone, dexamethasone plus ACTH, or captopril plus angiotensin II, but not in animals treated with captopril alone. The plasma concentration of corticosterone and the activity of 11 beta-hydroxylase in the inner adrenal layers were not changed. These findings indicate that alpha-MSH is specifically involved in the acute stimulation of the late steps of the secretory activity of the rat zona glomerulosa, and that this action of alpha-MSH requires a normal level of circulating angiotensin II.     

Comparative hemodynamic actions of ANF-related peptides in conscious sheep

The rapid hemodynamic effects of several N- and C-terminal deleted fragments of ANF, a potent ANF analogue and the recently characterised brain natriuretic peptide (BNP) were investigated in conscious sheep, and compared to the rapid hemodynamic actions of ANF 1-28. The hypotensive potency of all peptides studied was as follows: ANF 1-28 = PLO58 greater than 5-27 = ANF 5-28 = BNP greater than ANF 7-28 greater than ANF 13-28 = ANF 5-25. All peptides reduced blood pressure via a decrease in total peripheral resistance, excluding ANF 5-25 and 13-28 which were without effect on any parameter measured. These changes were associated with reflex increases in both heart rate and cardiac output, and a slight reduction in stroke volume. The duration of hypotensive/vasodilator action of ANF 1-28, 5-27, 5-28, 7-28 and BNP was approximately 3-4 minutes, whereas that of PLO58 was 7-8 minutes. In conclusion, amino acid deletions from the C- and N-terminal of the ANF molecule reduced the hypotensive/vasodilator potency of the peptide in conscious sheep. BNP produced similar rapid hemodynamic changes to ANF 1-28, suggesting that the two peptides may co-regulate blood pressure and possibly body fluids to promote fluid and cardiovascular homeostasis.     

Acute vascular and metabolic actions of the green tea polyphenol epigallocatechin 3-gallate in rat skeletal muscle

Epidemiological studies show a dose-dependent relationship between green tea consumption and reduced risk for type 2 diabetes and cardiovascular disease. Bioactive compounds in green tea including the polyphenol epigallocatechin 3-gallate (EGCG) have insulin-mimetic actions on glucose metabolism and vascular function in isolated cell culture studies. The aim of this study is to explore acute vascular and metabolic actions of EGCG in skeletal muscle of Sprague–Dawley rats. Direct vascular and metabolic actions of EGCG were investigated using surgically isolated constant-flow perfused rat hindlimbs. EGCG infused at 0.1, 1, 10 and 100 μM in 15 min step-wise increments caused dose-dependent vasodilation in 5-hydroxytryptamine pre-constricted hindlimbs. This response was not impaired by the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin or the AMP-kinase inhibitor Compound C. The nitric oxide synthase (NOS) inhibitor N^G-Nitro-l-Arginine Methyl Ester (L-NAME) completely blocked EGCG-mediated vasodilation at 0.1–10 μM, but not at 100 μM. EGCG at 10 μM did not alter muscle glucose uptake nor did it augment insulin-stimulated muscle glucose uptake. The acute metabolic and vascular actions of 10 μM EGCG in vivo were investigated in anaesthetised rats during a hyperinsulinemic-euglycemic clamp (10 mU min⁻¹ kg⁻¹ insulin). EGCG and insulin both stimulated comparable increases in muscle microvascular blood flow without an additive effect. EGCG-mediated microvascular action occurred without altering whole body or muscle glucose uptake. We concluded that EGCG has direct NOS-dependent vasodilator actions in skeletal muscle that do not acutely alter muscle glucose uptake or enhance the vascular and metabolic actions of insulin in healthy rats.     

Somatotropin increases protein balance independent of insulin's effects on protein metabolism in growing pigs

Somatotropin (ST) administration enhances protein deposition and elicits profound metabolic responses, including hyperinsulinemia. To determine whether the anabolic effect of ST is due to hyperinsulinemia, pair-fed weight-matched growing swine were treated with porcine ST (150 microg x kg body wt(-1) x day(-1)) or diluent for 7 days (n = 6/group, approximately 20 kg). Then pancreatic glucose-amino acid clamps were performed after an overnight fast. The objective was to reproduce the insulin levels of 1) fasted control and ST pigs (basal insulin, 5 microU/ml), 2) fed control pigs (low insulin, 20 microU/ml), and 3) fed ST pigs (high insulin, 50 microU/ml). Amino acid and glucose disposal rates were determined from the infusion rates necessary to maintain preclamp blood levels of these substrates. Whole body nonoxidative leucine disposal (NOLD), leucine appearance (R(a)), and leucine oxidation were determined with primed, continuous infusions of [(13)C]leucine and [(14)C]bicarbonate. ST treatment was associated with higher NOLD and protein balance and lower leucine oxidation and amino acid and glucose disposals. Insulin lowered R(a) and increased leucine oxidation, protein balance, and amino acid and glucose disposals. These effects of insulin were suppressed by ST treatment; however, the protein balance remained higher in ST pigs. The results show that ST treatment inhibits insulin's effects on protein metabolism and indicate that the stimulation of protein deposition by ST treatment is not mediated by insulin. Comparison of the protein metabolic responses to ST treatment during the basal fasting period with those in the fully fed state from a previous study suggests that the mechanism by which ST treatment enhances protein deposition is influenced by feeding status.     

Acute effects of corticosterone on tissue protein synthesis and insulin-sensitivity in rats in vivo.

The effect of corticosterone treatment on the sensitivity of muscle protein synthesis to insulin infusion was assessed in post-absorptive young rats. To select the optimal time period for corticosterone treatment, protein synthesis was measured by injection of L-[2,6-3H]phenylalanine (1.5 mmol/kg body weight) 1, 4, 12 or 24 h after injection of corticosterone (5 mg/kg body wt.). Muscle protein synthesis was significantly decreased at 4 h and the effect was maximal by 12 h; liver protein synthesis was elevated at 12 h and 24 h. The dose-response of muscle protein synthesis to a 30 min infusion with 0-150 munits of insulin/h was then compared in rats pretreated with corticosterone (10 mg/100 g body wt.) or vehicle alone. When no insulin was infused, corticosterone inhibited protein synthesis in gastrocnemius muscle. High doses of insulin stimulated protein synthesis, but the inhibition by corticosterone was similar to that in the absence of insulin. At intermediate doses of insulin there was an increased requirement for insulin to elicit an equivalent response in muscle protein synthesis. Plantaris muscle responded in a manner similar to that of gastrocnemius, but neither soleus muscle nor liver responded significantly to insulin. These data suggest that corticosterone has two modes of action; one which is independent from and opposite to that of insulin, and a second which causes insulin-resistance through a decrease in sensitivity rather than a change in responsiveness.     

桦木酸体内抗肿瘤作用的初步研究

目的研究桦木酸对H22、S180小鼠肿瘤细胞药效学作用及对肿瘤细胞膜Ca^2＋、Mg^2＋-ATP酶活性的影响。方法通过限量实验确定桦木酸的给药剂量。动物随机分为6组,分别为桦木酸500、250、125mg／kg剂量组,阳性对照组给予环磷酰胺（20mg／kg）,模型对照组分别给予相同体积的生理盐水和配药溶剂,灌胃给药。观察生命延长时间与瘤重抑制率;紫外分光光度法测定Ca^2＋、Mg^2＋-ATP酶活性,结果桦木酸使S180荷瘤小鼠肿瘤细胞膜Ca^2＋、Mg^2＋-ATP酶活性提高（P〈0．05）。结论桦木酸抗肿瘤作用机制与其上调肿瘤细胞膜p53蛋白的表达,改变肿瘤细胞膜Ca^2＋、Mg^2＋-ATP酶活性有关。     

Acute pulmonary hemodynamic effects of intravenous copper sulfate: role of alpha-adrenergic system

We investigated the acute pulmonary hemodynamic effects of intravenous copper sulfate (CuSO4) infusion and its mechanism of action in six groups of conscious sheep (total 40). After 300 mg CuSO4 alone, mean pulmonary artery pressure (Ppa) increased from 10.3 to 22.5 Torr and pulmonary artery wedge pressure (Ppaw) from 3.5 to 7.6 Torr, whereas systemic arterial pressure (Psa) increased from 95 to 102 Torr. Cardiac output (Qp) decreased from 4.7 to 3.3 l/min. Pulmonary vascular resistance (PVR) and systemic vascular resistance (SVR) increased to 320 and 160% of base line, respectively. The hemodynamic changes correlated well with serum copper, which increased from a base-line value of 0.12 to 3.5 mg/dl after the CuSO4. Serum dopamine beta-hydroxylase increased from 3.2 U/l before CuSO4 injection to 5.7 after its administration, signifying activation of adrenergic nervous system. H1-histamine receptor blockade with chlorpheniramine failed to prevent the effects of CuSO4. Pretreatment with methysergide, a serotonin antagonist, partially attenuated the effects of CuSO4. Phenoxybenzamine, an alpha-adrenergic receptor blocker, and 6-hydroxydopamine, a catecholamine depleting agent, completely blocked the effects of CuSO4. beta-Adrenergic receptor blockade with propranolol enhanced the effects of CuSO4. We conclude, that, in conscious sheep, acute infusion of CuSO4 caused a marked reversible increase in PVR with a slight transient increase in SVR, and this pulmonary hypertension was produced by stimulation of the alpha-adrenergic nervous system.     

Polo-like kinases inhibited by wortmannin. Labeling site and downstream effects

Polo-like kinases play crucial roles throughout mitosis. We previously reported that wortmannin potently inhibits Polo-like kinase 1 (Plk1). In this study, we show that wortmannin also strongly inhibits Polo-like kinase 3 (Plk3). To further characterize this inhibition, we identified the sites of labeling on Plk1 and Plk3 targeted by AX7503, a tetramethylrhodamine-wortmannin conjugate. AX7503 labeling on Plk1 and Plk3 was found to occur on a conserved ATP binding site residue. In addition, we show that wortmannin inhibits Plk3 activity in live cells at concentrations commonly used to inhibit the more well known targets of wortmannin, the phosphoinositide 3-kinases. Importantly, we found that inhibition of Plk3 by wortmannin lead to a decrease in phosphorylation of p53 on serine 20 induced by DNA damage, demonstrating the effect of wortmannin on a downstream Plk3 target. Taken together, our results suggest that wortmannin can affect multiple functions of Plk3 in cell cycle progression and at the DNA damage check point. The identification of the labeling sites of Plk1 and Plk3 by AX7503 may be useful in designing more effective compounds to target Polo-like kinases for cancer treatment and also may be useful for the structural study of Plk domains.     

Acute cytogenetic effects of potassium bromate on rat bone marrow cells in vivo

The acute cytogenetic effects of potassium bromate (KBrO3) on rat bone marrow cells in vivo were studied. The incidence of chromosome aberrations in bone marrow cells increased rapidly, reaching a maximum level 12 h after intraperitoneal injection and decreased within 24 h. Dose-response relationships were obtained for both intraperitoneal and oral administrations.