Studies on regulatory mechanisms of heme biosynthesis in hepatocytes from normal and experimental-diabetic rats. Role of insulin

1990 ◽  
Vol 68 (6) ◽  
pp. 914-921 ◽  
Author(s):  
Eduardo T. Cánepa ◽  
Elena B. C. Llambías ◽  
Moisés Grinstein
Keyword(s):  
Aminolevulinic Acid ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Inhibitory Effect ◽  
Diabetic Rats ◽  
Significant Inhibition ◽  
Diabetic Rat ◽  
Experimental Conditions ◽  
Cytochrome P 450

In the present work we demonstrate that insulin decreases the phenobarbital-induced activities of δ-aminolevulinic acid synthase and ferrochelatase in isolated hepatocytes from normal and experimental-diabetic rats. Insulin concentrations required to produce significant inhibition in diabetic hepatocytes were higher than in normal cells. Under similar experimental conditions, insulin decreased the basal activities of δ-aminolevulinic acid synthase and ferrochelatase in hepatocytes from normal rats; no inhibitory effect was observed on the basal activity of δ-aminolevulinic acid synthase in hepatocytes from diabetic rats. Cytochrome P-450 content of both normal and diabetic cells was not affected by insulin in absence or presence of phenobarbital. The inhibitory action of insulin was exerted even when effective concentrations of glucagon, dexamethasone, or 8-(p-chlorophenylthio)-cAMP were present.Key words: δ-aminolevulinic acid synthase, ferrochelatase, cAMP, insulin, diabetic rat hepatocytes.

Studies on regulatory mechanisms of heme biosynthesis in hepatocytes from normal and experimental-diabetic rats. Role of cAMP

1989 ◽  
Vol 67 (11-12) ◽  
pp. 751-758 ◽  
Author(s):  
Eduardo T. Cánepa ◽  
Elena B. C. Llambías ◽  
Moisés Grinstein
Keyword(s):  
Aminolevulinic Acid ◽  
Rat Hepatocytes ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Intracellular Camp ◽  
Induction Effect ◽  
Isolated Rat Hepatocytes ◽  
Camp Content ◽  
Cytochrome P 450 ◽  
Phenobarbital Induction

In the present work we have been able to demonstrate the existence of some interrelationship between intracellular level of cAMP content and phenobarbital induction of δ-aminolevulinic acid synthase, ferrochelatase, and cytochrome P-450 biosynthesis in isolated rat hepatocytes. The increase of the level of intracellular cAMP produced by activators of adenylate cyclase, inhibitors of phosphodiesterase, or added cyclic nucleotides is reflected by an increase of the phenobarbital induction effect. The greater induction observed in hepatocytes of diabetic rats may be due to a higher level of the intracellular cAMP. The lack of potentiation of added cAMP in diabetic cells is mainly due to the fact that the maximum induction that could be attained is already achieved by the effect of the preexisting high level of the endogenous cAMP.Key words: δ-aminolevulinic acid synthase, ferrochelatase, cytochrome P-450, cAMP, diabetic rat hepatocytes.

cAMP regulation of phenobarbital-mediated induction of δ-aminolevulinate synthase mRNA in hepatocytes from normal and experimental diabetic rats

1994 ◽  
Vol 72 (9-10) ◽  
pp. 381-390 ◽  
Author(s):  
Cecilia L. Varone ◽  
Eduardo T. Canépa ◽  
Elena B. C. Llambías ◽  
Moisés Grinstein
Keyword(s):  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Dibutyryl Camp ◽  
Dependent Protein Kinase ◽  
Normal Cells ◽  
Aminolevulinate Synthase ◽  
Maximum Activation ◽  
Dependent Protein

We examined the mechanism underlying the effect of cAMP on δ-aminolevulinate synthase mRNA biosynthesis in isolated hepatocytes from normal and experimental diabetic rats. We have demonstrated that the potentiation by dibutyryl cAMP of the phenobarbital-mediated induction of δ-aminolevulinate synthase enzyme activity, observed in our previously reported studies, reflects an increased amount of its mRNA. The inducing effect exerted by phenobarbital on the biosynthesis of δ-aminolevulinate synthase mRNA in diabetic hepatocytes is greater than that observed in normal cells. This enhanced response to the increased level of endogenous cAMP in diabetic hepatocytes is apparently sufficient for a maximum activation of the cAMP-dependent protein kinase. The present results suggest that in rat liver dibutyryl cAMP modulates δ-aminolevulinate synthase mRNA biosynthesis by acting predominantly, if not exclusively, at the level of gene transcription.Key words: δ-aminolevulinate synthase mRNA, phenobarbital, cAMP, diabetic rat hepatocytes.

Regulation of lipoprotein lipase activity in cardiac myocytes from control and diabetic rat hearts by plasma lipids

1992 ◽  
Vol 70 (9) ◽  
pp. 1271-1279 ◽  
Author(s):  
Brian Rodrigues ◽  
Janice E. A. Braun ◽  
Michael Spooner ◽  
David L. Severson
Keyword(s):  
Lipoprotein Lipase ◽  
Cardiac Myocytes ◽  
Lipase Activity ◽  
Plasma Lipids ◽  
Inhibitory Effect ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Lipoprotein Lipase Activity ◽  
Triton Wr 1339 ◽  
Plasma Triacylglycerol

The objective of this investigation was to test the hypothesis that the diabetes-induced reduction in lipoprotein lipase activity in cardiac myocytes may be due to hypertriglyceridemia. Administration of 4-aminopyrazolopyrimidine (50 mg/kg) to control rats for 24 h reduced plasma triacylglycerol levels and increased the heparin-induced release of lipoprotein lipase into the incubation medium of cardiac myocytes. The acute (3–5 days) induction of diabetes by streptozotocin (100 mg/kg) produced hypertriglyceridemia and reduced heparin-releasable lipoprotein lipase activity in cardiac myocytes. Treatment of diabetic rats with 4-aminopyrazolopyrimidine resulted in a fall in plasma triacylglycerol content and increased heparin-releasable lipoprotein lipase activity. Administration of Triton WR-1339 also resulted in hypertriglyceridemia, but the heparin-induced release of lipoprotein lipase from control cardiac myocytes was not reduced in the absence of lipolysis of triacylglycerol-rich lipoproteins. Treatment with Triton WR-1339 did, however, increase the heparin-induced release of lipoprotein lipase from diabetic cardiac myocytes. Preparation of cardiac myocytes with 0.9 mM oleic acid resulted in a decrease in both total cellular and heparin-releasable lipoprotein lipase activities. These results suggest that the diabetes-induced reduction in heart lipoprotein lipase activity may, at least in part, be due to an inhibitory effect of free fatty acids, derived either from lipoprotein degradation or from adipose tissue lipolysis, on lipoprotein lipase activity in (and (or) release from) cardiac myocytes.Key words: diabetes, plasma triacylglycerols, cardiac myocytes, lipoprotein lipase.

scholarly journals Evidence that Ca2+-release-activated Ca2+ channels in rat hepatocytes are required for the maintenance of hormone-induced Ca2+ oscillations

2003 ◽  
Vol 370 (2) ◽  
pp. 695-702 ◽  
Author(s):  
Roland B. GREGORY ◽  
Gregory J. BARRITT
Keyword(s):  
High Selectivity ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Cation Channels ◽  
Isolated Rat Hepatocytes ◽  
Pharmacological Agents ◽  
Crac Channels ◽  
Kinetics Of ◽  
Ca2 Channels

Store-operated Ca2+ channels in liver cells have been shown previously to exhibit a high selectivity for Ca2+ and to have properties indistinguishable from those of Ca2+-release-activated Ca2+ (CRAC) channels in mast cells and lymphocytes [Rychkov, Brereton, Harland and Barritt (2001) Hepatology 33, 938—947]. The role of CRAC channels in the maintenance of hormone-induced oscillations in the cytoplasmic free Ca2+ concentration ([Ca2+]cyt) in isolated rat hepatocytes was investigated using several inhibitors of CRAC channels. 2-Aminoethyl diphenylborate (2-APB; 75μM), Gd3+ (1μM) and 1-{β-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl}-1H-imidazole hydrochloride (SK&F 96365; 50μM) each inhibited vasopressin- and adrenaline (epinephrine)-induced Ca2+ oscillations (measured using fura-2). The characteristics of this inhibition were similar to those of inhibition caused by decreasing the extracellular Ca2+ concentration to zero by addition of EGTA. The effect of 2-APB was reversible. In contrast, LOE-908 {(R,S)-(3,4-dihydro-6,7-dimethoxy-isochinolin-1-yl)-2-phenyl-N,N-di[2-(2,3,4-trimethoxyphenyl)ethyl]acetamidemesylate}(30μM), used commonly to block Ca2+ inflow through intracellular-messenger-activated, non-selective cation channels, did not inhibit the Ca2+ oscillations. In the absence of added extracellular Ca2+, 2-APB, Gd3+ and SK&F 96365 did not alter the kinetics of the increase in [Ca2+]cyt induced by a concentration of adrenaline or vasopressin that induces continuous Ca2+ oscillations at the physiological extracellular Ca2+ concentration. Ca2+ inflow through non-selective cation channels activated by maitotoxin could not restore Ca2+ oscillations in cells treated with 2-APB to block Ca2+ inflow through CRAC channels. Evidence for the specificity of the pharmacological agents for inhibition of CRAC channels under the conditions of the present experiments with hepatocytes is discussed. It is concluded that Ca2+ inflow through CRAC channels is required for the maintenance of hormone-induced Ca2+ oscillations in isolated hepatocytes.

Sexual dysfunction in the diabetic BB/WOR rat: a role of central neuropathy

1997 ◽  
Vol 272 (1) ◽  
pp. R259-R267 ◽  
Author(s):  
K. T. McVary ◽  
C. H. Rathnau ◽  
K. E. McKenna
Keyword(s):  
Sexual Function ◽  
Diabetic Rats ◽  
Nerve Fibers ◽  
Diabetic Rat ◽  
Penile Erections ◽  
Reflex Testing ◽  
Diabetic Impotence ◽  
Central Neuropathy ◽  
Sexual Reflexes

The pathophysiological mechanisms of diabetic impotence remain obscure. We have presented an analysis of sexual function in a diabetic rat (BB/WOR) model characterized by diffuse neuropathic changes without a confounding vasculopathy that allows us to define the neural components of erectile failure. Copulatory behavioral testing demonstrated that diabetic males were severely impaired: the controls mounted three times more than the diabetics and had about one-half the latency to first mount. The diabetics had about one-fourth the number of intromissions and took nearly twice as long to achieve first ejaculation. The number of ejaculations was drastically reduced as well. We examined sexual reflexes in the anesthetized acutely spinalized rat. These experiments tested the integrity of spinal circuits controlling sexual function. Reflex testing demonstrated that spinal sexual reflexes were also severely impaired: the onset latency of reflexes was more than doubled, and the duration of reflexes was less than one-half. More than one-half of the diabetic rats showed no penile erections. Neural studies showed even more derangement in reflex measures in rats, without erection. Nerve conduction velocity experiments suggested a peripheral neuropathic change in hypogastric nerve and motor pudendal nerve fibers. These dysfunctional findings were seen without any androgen deficiency. These results indicate that diabetic impotence in this model reflects central and peripheral neuropathic disease processes.

scholarly journals Taurolithocholate-induced Ca2+ release is inhibited by phorbol esters in isolated hepatocytes

1992 ◽  
Vol 287 (3) ◽  
pp. 891-896 ◽  
Author(s):  
L Combettes ◽  
B Berthon ◽  
M Claret
Keyword(s):  
Bile Acid ◽  
Bile Acids ◽  
Phorbol Ester ◽  
Phorbol Esters ◽  
Rat Hepatocytes ◽  
Isolated Hepatocytes ◽  
Inhibitory Effect ◽  
Cell Uptake ◽  
Intracellular Binding ◽  
Pkc Activation

The monohydroxy bile acid taurolithocholate (TLC) causes a rapid and transient increase in free cytosolic Ca2+ concentration ([Ca2+]i) in suspensions of rat hepatocytes similar to that elicited by the InsP3-dependent hormone vasopressin. The effect of the bile acid is due to a mobilization of Ca2+, independent of InsP3, from the endoplasmic reticulum (ER). Short-term preincubation of cells with the phorbol ester 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (PMA), which activates protein kinase C (PKC), blocked the increase in [Ca2+]i induced by TLC, but did not alter that mediated by vasopressin. We obtained the following results, indicating that the effect of PMA is mediated by the activation of PKC. (1) Phorbol esters were effective over a concentration range where they activate PKC (IC50 = 0.5 nM); (2) phorbol esters that do not activate PKC did not inhibit the effects of TLC; (3) the permeant analogue oleoylacetylglycerol mimicked the inhibitory effect of PMA; (4) lastly, the inhibition of the TLC-induced Ca2+ mobilization by phorbol esters was partially prevented by preincubating the cells with the PKC inhibitors H7 and AMG-C16. Preincubating hepatocytes with PMA had no effect on the cell uptake of labelled TLC, indicating that the phorbol ester does not interfere with the transport system responsible for the accumulation of bile acids. In saponin-treated liver cells, PMA added before or after permeabilization failed to abolish TLC-induced Ca2+ release from the ER. The possibility is discussed that PMA, via PKC activation, may alter the intracellular binding or the transfer of bile acids in the liver.

Role of cytochrome P-450 arachidonate metabolites in endothelin signaling in rat proximal tubule

2002 ◽  
Vol 282 (1) ◽  
pp. F144-F150 ◽  
Author(s):  
Bruno A. Escalante ◽  
John C. McGiff ◽  
Adebayo O. Oyekan
Keyword(s):  
Proximal Tubule ◽  
Inhibitory Action ◽  
Inhibitory Effect ◽  
Gas Chromatography Mass Spectrometry ◽  
Arachidonate Metabolites ◽  
Endogenous Release ◽  
Oxide Synthase ◽  
Cytochrome P 450 ◽  
Rat Proximal Tubule

We examined the rat proximal tubule (PT) response to endothelin-1 (ET-1) in terms of 20-hydroxyeicosatetraenoic acid (HETE) dependency. Arachidonic acid (AA) (1 μM) decreased ouabain-sensitive 86Rb uptake from 2.1 ± 0.1 to 0.3 ± 0.08 ng Rb · 10 μg protein−1 · 2 min−1( P < 0.05); 20-HETE (1 μM) had similar effects. Dibromododecenoic acid (DBDD) (2 μM), an inhibitor of ω-hydroxylase, abolished the inhibitory action of AA on86Rb uptake whereas the PT response to 20-HETE was unaffected. ET-1 at 0.1, 1, 10, and 100 nM reduced 86Rb uptake from 2.8 ± 0.3 in control PTs to 2.4 ± 0.2, 1.7 ± 0.1, 0.67 ± 0.08, and 0.1 ± 0.03 ng Rb · 10 μg protein−1 · 2 min−1, respectively. DBDD (2 μM) abolished the inhibitory effect of ET-1 on86Rb uptake as did BMS182874 (1 μM), an ETA-selective receptor antagonist. ET-1 (100 nM) significantly increased PT 20-HETE release by ∼50%, an effect prevented by DBDD. N ω-nitro-l-arginine-methyl ester (l-NAME), given for 4 days to inhibit nitric oxide synthase (NOS), increased arterial pressure from 92 ± 12 to 140 ± 8 mmHg and increased endogenous release of 20-HETE from isolated PTs (measured by gas chromatography/mass spectrometry). Inl-NAME-treated PTs, but not in control PTs, 0.1 μM AA inhibited ouabain-sensitive 86Rb uptake by >40%; the response to AA was attenuated by DBDD. We conclude that, in the PTs, 1) 20-HETE is a second messenger for ET-1 and 2) conversion of AA to 20-HETE is augmented when NOS is inhibited.

scholarly journals THE ROLE OF METHIONINE DEFICIENCY IN POLIOVIRUS REPLICATION IN TISSUE CULTURES

1966 ◽  
Vol 123 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Soussan Mohajer ◽  
Janis Gabliks
Keyword(s):  
Amino Acids ◽  
Hela Cells ◽  
Inhibitory Effect ◽  
Monkey Kidney ◽  
Kidney Cells ◽  
Tissue Cultures ◽  
Experimental Conditions ◽  
Methionine Deficiency ◽  
Intracellular Amino Acids

The role of methionine in poliovirus infection in HeLa and monkey kidney cells was investigated by using the methionine analogue l-ethionine. In the presence of 2.0 x 10–3 and 4.0 x 10–3 moles ethionine, the growth of HeLa and monkey kidney cells was significantly inhibited. Under the same experimental conditions, ethionine had no significant effect on the biosynthesis of two strains of poliovirus (Mahoney and Lansing) in HeLa cells, whereas in primary monkey kidney cells, it markedly inhibited the biosynthesis of the Lansing strain of poliovirus. HeLa cells partly depleted of their intracellular amino acids did not change the rate of viral biosynthesis. The inhibitory effect of ethionine on cell growth and viral biosynthesis was reversed by addition of an excess of l-methionine.

scholarly journals Modification of vasodilator response in streptozotocin-induced diabetic rat

1999 ◽  
Vol 77 (12) ◽  
pp. 980-985 ◽  
Author(s):  
Jean-François Bouchard ◽  
Éric C Dumont ◽  
Daniel Lamontagne
Keyword(s):  
Diabetes Mellitus ◽  
Adenylyl Cyclase ◽  
Dose Response ◽  
Vascular Reactivity ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Response Curves ◽  
Experimental Conditions ◽  
Isolated Hearts ◽  
Dose Response Curves

Functional dilatory response in streptozotocin-induced diabetic rats was investigated using thoracic aortas, isolated hearts, and mesenteric beds. Dose-response curves to the PGI2 analogue iloprost on phenylephrine-preconstricted rings of diabetic rats and controls were comparable. In contrast, decreased vasodilation in diabetic rats was observed when dose-response curves to iloprost were performed in hearts and on phenylephrine-preconstricted mesenteric beds. Dose-response curves to forskolin, an adenylyl cyclase activator, performed with hearts and phenylephrine-preconstricted aortic rings and isolated mesenteric beds of diabetic rats and controls were comparable. However, a decreased vasodilation to the ATP-sensitive potassium channel (KATP) activator lemakalim was observed in diabetic hearts, but not in aortic rings and mesenteric beds. In conclusion, under our experimental conditions, diabetes mellitus affects the vasodilation to iloprost in both coronary and mesenteric beds, but not in the aorta. In the heart, this modification of vascular reactivity may be due to a decrease in KATP channel mediated response and not to a decreased activity of adenylyl cyclase. At this time, in the isolated mesenteric bed, the mechanism of this modification in vascular reactivity remains unknown.Key words: diabetes mellitus, iloprost, KATP channels, adenylyl cyclase, aorta, coronary circulation, mesenteric bed.

The effects of chronic trimetazidine treatment on mechanical function and fatty acid oxidation in diabetic rat hearts

2007 ◽  
Vol 85 (5) ◽  
pp. 527-535 ◽  
Author(s):  
Arzu Onay-Besikci ◽  
Sahika Guner ◽  
Ebru Arioglu ◽  
Isil Ozakca ◽  
A. Tanju Ozcelikay ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Fatty Acid Oxidation ◽  
Coronary Flow ◽  
Contractile Function ◽  
Inhibitory Effect ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Acid Oxidation ◽  
Mechanical Function ◽  
Oxidation Rates

Clinical and experimental evidence suggest that increased rates of fatty acid oxidation in the myocardium result in impaired contractile function in both normal and diabetic hearts. Glucose utilization is decreased in type 1 diabetes, and fatty acid oxidation dominates for energy production at the expense of an increase in oxygen requirement. The objective of this study was to examine the effect of chronic treatment with trimetazidine (TMZ) on cardiac mechanical function and fatty acid oxidation in streptozocin (STZ)-diabetic rats. Spontaneously beating hearts from male Sprague–Dawley rats were subjected to a 60-minute aerobic perfusion period with a recirculating Krebs–Henseleit solution containing 11 mmol/L glucose, 100 μU/mL insulin, and 0.8 mmol/L palmitate prebound to 3% bovine serum albumin (BSA). Mechanical function of the hearts, as cardiac output × heart rate (in (mL/min)·(beats/min)·10–2), was deteriorated in diabetic (73 ± 4) and TMZ-treated diabetic (61 ± 7) groups compared with control (119 ± 3) and TMZ-treated controls (131 ± 6). TMZ treatment increased coronary flow in TMZ-treated control (23 ± 1 mL/min) hearts compared with untreated controls (18 ± 1 mL/min). The mRNA expression of 3-ketoacyl-CoA thiolase (3-KAT) was increased in diabetic hearts. The inhibitory effect of TMZ on fatty acid oxidation was not detected at 0.8 mmol/L palmitate in the perfusate. Addition of 1 μmol/L TMZ 30 min into the perfusion did not affect fatty acid oxidation rates, cardiac work, or coronary flow. Our results suggest that higher expression of 3-KAT in diabetic rats might require increased concentrations of TMZ for the inhibitory effect on fatty acid oxidation. A detailed kinetic analysis of 3-KAT using different concentrations of fatty acid will determine the fatty acid inhibitory concentration of TMZ in diabetic state where plasma fatty acid levels are increased.

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