Regulation of phenobarbital-induced ferrochelatase mRNA activity by dibutyryl cAMP and glucose in normal and diabetic rat hepatocytes

1992 ◽  
Vol 70 (1) ◽  
pp. 26-33 ◽  
Author(s):  
Eduardo T. Cánepa ◽  
Marcelo Páez Pereda ◽  
Elena B. C. Llambías ◽  
Moïses Grinstein
Keyword(s):  
Experimental Evidence ◽  
Rat Hepatocytes ◽  
Diabetic Rat ◽  
Dibutyryl Camp ◽  
Glucose Effect ◽  
Normal Cells ◽  
Camp Content ◽  
Normal Rat ◽  
Increased Activity

The induction of ferrochelatase activity by phenobarbital and its potentiation by dibutyryl cAMP assayed in normal rat hepatocytes are associated with increased activity of ferrochelatase mRNA. Glucose inhibits this stimulatory effect. This inhibition can be reversed with increasing concentrations of dibutyryl cAMP. The inducing effect exerted by phenobarbital on the activity of ferrochelatase mRNA in diabetic hepatocytes is greater than that observed in normal cells. This enhanced response in diabetic rat hepatocytes is neither potentiated by adding dibutyryl cAMP nor repressed by glucose. The absence of a glucose effect persists even when the endogenous cAMP content is lowered to normal levels. The results obtained in this study are consistent with those reported in other published studies of ferrochelatase activity. This adds more experimental evidence to support the concept that ferrochelatase is inducible. The results obtained suggest that ferrochelatase is more susceptible to induction with phenobarbital in diabetic rat hepatocytes than in normal rat hepatocytes.Key words: ferrochelatase mRNA activity, phenobarbital, cAMP, glucose, diabetic rat hepatocytes.

Glucose inhibits phenobarbital-induced δ-aminolevulinate synthase expression in normal but not in diabetic rat hepatocytes

1996 ◽  
Vol 74 (2) ◽  
pp. 271-281 ◽  
Author(s):  
Cecilia L. Varone ◽  
Eduardo T. Cánepa ◽  
Elena B. C. Llambías ◽  
Moisés Grinstein
Keyword(s):  
Phosphodiesterase Inhibitor ◽  
Rat Hepatocytes ◽  
Inhibitory Effect ◽  
Diabetic Rat ◽  
Glucose Effect ◽  
Camp Content ◽  
Aminolevulinate Synthase ◽  
Abnormal Metabolism ◽  
Normal Rat ◽  
Mrna Half Life

In the present work, we demonstrate the presence of a glucose inhibitory effect on the phenobarbital-mediated induction of the δ-aminolevulinate synthase mRNA in normal rat hepatocytes, consistent with the results obtained with the δ-aminolevulinate synthase activity previously reported. This "glucose effect" can be prevented by adding cAMP, adenylate cyclase activators, or a phosphodiesterase inhibitor. δ-Aminolevulinate synthase mRNA half-life is not modified in the presence of phenobarbital or glucose. When the same experiments are performed using diabetic cells, no glucose effect is observed, even when the endogenous cAMP content is lowered to normal levels. The results obtained in this study suggest that glucose decreases δ-aminolevulinate synthase biosynthesis by acting at a pretranslational step. Assuming that the glucose effect operates by a repression mechanism exerted by metabolites derived from or related to glucose, the present results may reflect a derangement in the formation of these metabolites as a result of the abnormal metabolism operating in the diabetic state.Key words: glucose, δ-aminolevulinate synthase expression, diabetic rat hepatocytes, phenobarbital, cAMP.

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.

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.

Immunoenzymatic demonstration of the simultaneous presence of transferrin, hemopexin and albumin in a same hepatocyte and their ultrastructural localization

1978 ◽  
Vol 36 (2) ◽  
pp. 88-89
Author(s):  
M. Kraemer ◽  
J. Foucrier ◽  
J. Vassy ◽  
M.T. Chalumeau
Keyword(s):  
Plasma Proteins ◽  
Rat Hepatocytes ◽  
Ultrastructural Localization ◽  
Carrier Proteins ◽  
Normal Cells ◽  
Adult Rat ◽  
Adult Rat Hepatocytes ◽  
Monospecific Antisera ◽  
Different Levels

Some authors using immunofluorescent techniques had already suggested that some hepatocytes are able to synthetize several plasma proteins. In vitro studies on normal cells or on cells issued of murine hepatomas raise the same conclusion. These works could be indications of an hepatocyte functionnal non-specialization, meanwhile the authors never give direct topographic proofs suitable with this hypothesis.The use of immunoenzymatic techniques after obtention of monospecific antisera had seemed to us useful to bring forward a better knowledge of this problem. We have studied three carrier proteins (transferrin = Tf, hemopexin = Hx, albumin = Alb) operating at different levels in iron metabolism by demonstrating and localizing the adult rat hepatocytes involved in their synthesis.Immunological, histological and ultrastructural methods have been described in a previous work.

scholarly journals 3-oxo acid coenzyme A-transferase in normal and diabetic rat muscle

1976 ◽  
Vol 158 (2) ◽  
pp. 509-512 ◽  
Author(s):  
A Fenselau ◽  
K Wallis
Keyword(s):  
Skeletal Muscle ◽  
Coenzyme A ◽  
Substrate Inhibition ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Functional Parameters ◽  
Rat Muscle ◽  
Coa Transferase ◽  
Normal Rat ◽  
Streptozotocin Diabetic Rats

The amounts of succinyl-CoA--3-oxo acid CoA-transferase (EC 2.8.3.5) decrease progressively in skeletal muscle in streptozotocin-diabetic rats, reaching after 10 days about 50% of the value in normal rat muscle. Electrofocusing studies indicate the occurrence of partial proteolysis of the enzyme in diabetic muscle. However, several functional parameters relating to acetoacetate utilization, including substrate inhibition, are quite similar for muscle transferase preparations from normal and diseased rats. The development of pathological ketoacidosis is discussed in the light of these observations.

Tolbutamide inhibits glucagon-induced phosphorylation of 6PF-2-K/Fru-2,6-P2ase in rat hepatocytes

1995 ◽  
Vol 268 (3) ◽  
pp. E391-E396
Author(s):  
H. Ayame ◽  
A. Matsutani ◽  
H. Inoue ◽  
T. Kaneko ◽  
K. Kaku
Keyword(s):  
Rat Hepatocytes ◽  
Bifunctional Enzyme ◽  
Dependent Manner ◽  
Enzyme Protein ◽  
Dependent Protein ◽  
Sulfonylurea Drugs ◽  
Dose Dependent ◽  
Increased Activity ◽  
Reduced Activity

In previous studies, we demonstrated that tolbutamide inhibits a phosphorylation of hepatic 6-phosphofructo-2-kinase (6PF-2-K)/fructose-2,6-bisphosphatase (Fru-2,6-P2ase) catalyzed by the adenosine 3',5'-cyclic monophosphate-dependent protein kinase in a reconstruction system using the purified enzyme from the rat liver. In the current study, to assess a role of tolbutamide on hepatic 6PF-2-K/Fru-2,6-P2ase physiologically, we used intact rat hepatocytes and examined effects of tolbutamide on a phosphorylation of the bifunctional enzyme in the presence of glucagon. Glucagon induced a rapid phosphorylation of hepatic 6PF-2-K/Fru-2,6-P2ase accompanied by an inhibition of 6PF-2-K activity and a stimulation of Fru-2,6-P2ase activity in a dose-dependent manner. Tolbutamide inhibited glucagon-induced phosphorylation of the bifunctional enzyme protein in a dose-dependent manner. By adding 2 mM tolbutamide, reduced activity of 6PF-2-K and increased activity of Fru-2,6-P2ase in the presence of 10(-9) M glucagon were partially restored. The present results suggest the possibility that tolbutamide modulates the activity of hepatic 6PF-2-K/Fru-2,6-P2ase through inhibiting a phosphorylation of the enzyme protein. The counterregulatory influence of tolbutamide on the effect of glucagon suggests a possible mechanism for the extrapancreatic effect of sulfonylurea drugs.

Effect of experimental diabetes on rat cardiac cAMP, phosphorylase, and inotropy

1983 ◽  
Vol 244 (6) ◽  
pp. H844-H851 ◽  
Author(s):  
R. V. Vadlamudi ◽  
J. H. McNeill
Keyword(s):  
Experimental Diabetes ◽  
Diabetic Rats ◽  
Diabetic Rat ◽  
Phosphorylase Activity ◽  
Camp Content ◽  
Rat Hearts ◽  
Underlying Causes ◽  
Camp Levels ◽  
Working Rat Heart ◽  
Time Point

The isolated perfused working rat heart was used to study experimental diabetes-induced alterations in the effect of isoproterenol on adenosine 3',5'-cyclic monophosphate (cAMP) content, inotropy, and phosphorylase activity. Experimental diabetes was induced by intravenous injection of either alloxan (40 mg/kg) or streptozotocin (50 mg/kg). There were no changes in either basal cAMP levels or in isoproterenol-induced cAMP levels in hearts from diabetic rats at either 3 days or 100-120 days after induction of diabetes. Maximum changes produced by isoproterenol in positive and negative dP/dt developments of diabetic rat hearts were also not different from control at either time point. However, phosphorylase was activated to a significantly greater extent by isoproterenol in hearts obtained from acute as well as chronic diabetic rats. Chronic diabetic rat hearts exhibited significantly higher total phosphorylase activity. Diabetic rat hearts had slightly but not significantly higher basal phosphorylase a activity. Furthermore, prostaglandin E1 activated phosphorylase in diabetic rat hearts but not in control rat hearts. Acute metabolic derangements and alterations in Ca2+ homeostasis caused by diabetes could be the underlying causes for this phosphorylase response. Thyroid hormone levels were depressed in diabetic rats. However, hypothyroidism is probably not responsible for the alterations in phosphorylase activity.

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.

Bioassay of endothelium-derived relaxing factor in diabetic rat aorta

1992 ◽  
Vol 263 (3) ◽  
pp. H676-H680 ◽  
Author(s):  
G. M. Pieper ◽  
D. A. Mei ◽  
P. Langenstroer ◽  
S. T. O'Rourke
Keyword(s):  
Rat Aorta ◽  
Diabetic Rat ◽  
Arginine Infusion ◽  
Relaxing Factor ◽  
Oxygen Derived Free Radicals ◽  
Donor Segment ◽  
Normal Rat ◽  
Bioassay Technique ◽  
Endothelium Derived Relaxing Factor ◽  
A Site

The bioassay technique was utilized to quantitate endothelium-derived relaxing factor (EDRF) released from perfused donor segments of control and diabetic rat aorta. In the presence of indomethacin, perfusates of donor segments with endothelium were allowed to superfuse recipient detector rings of normal rat aorta without endothelium. Under basal conditions, relaxations of the bioassay rings to perfusates of control and diabetic donor segments were similar. Perfusion of donor segments with acetylcholine produced relaxation of bioassay rings, which was decreased from endothelial perfusion of diabetic donor segments. These relaxations were inhibited by addition of methylene blue to the detector ring or by perfusion of donor segments with nitro-L-arginine. Infusion of superoxide dismutase (SOD) at a site proximal to the donor segment normalized relaxations induced by acetylcholine addition to diabetic donors. In contrast, infusion of SOD distal to the donor had no effect on acetylcholine-stimulated relaxations of detector rings from control donors while attenuating, paradoxically, the relaxations of detector rings from diabetic donors. These results suggest that diabetic rat aortas release similar levels of EDRF in response to acetylcholine, but the action of EDRF arising from diabetic donors is attenuated by enhanced release of oxygen-derived free radicals, which limits EDRF-mediated relaxation of vascular smooth muscle.

HYPOGLYCEMIC DRUGS AND THE DEXTRAN 'ANAPHYLACTOID' INFLAMMATION

1960 ◽  
Vol 38 (1) ◽  
pp. 823-827 ◽  
Author(s):  
V. W. Adamkiewicz ◽  
R. J. Fitko ◽  
A. A. Fortier
Keyword(s):  
Alloxan Diabetes ◽  
Diabetic Rat ◽  
Normal Rat ◽  
Hypoglycemic Drug

Tolbutamide (Orinase) (260 mg/kg s.c), a hypoglycemic drug of the sulphonylurea class, sensitizes the normal rat (135–185 g) towards the 'anaphylactoid' inflammation induced by the administration of dextran (1 ml 6% w/v solution in saline s.c. per rat). However, the drug does not sensitize the alloxan diabetic rat towards this inflammation, nor does it alleviate the classical signs of alloxan diabetes. It is suggested that the sensitization of normal rats towards dextran by tolbutamide is mediated through insulin.

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