scholarly journals Inhibition of the low-Km mitochondrial aldehyde dehydrogenase by diethyl maleate and phorone in vivo and in vitro Implications for formaldehyde metabolism

1986 ◽  
Vol 240 (3) ◽  
pp. 821-827 ◽  
Author(s):  
E Dicker ◽  
A I Cederbaum
Keyword(s):  
Aldehyde Dehydrogenase ◽  
Isolated Hepatocytes ◽  
Product Formation ◽  
Formaldehyde Dehydrogenase ◽  
Diethyl Maleate ◽  
Mitochondrial Fractions ◽  
Formaldehyde Oxidation ◽  
Formaldehyde Metabolism

Formaldehyde can be oxidized primarily by two different enzymes, the low-Km mitochondrial aldehyde dehydrogenase and the cytosolic GSH-dependent formaldehyde dehydrogenase. Experiments were carried out to evaluate the effects of diethyl maleate or phorone, agents that deplete GSH from the liver, on the oxidation of formaldehyde. The addition of diethyl maleate or phorone to intact mitochondria or to disrupted mitochondrial fractions produced inhibition of formaldehyde oxidation. The kinetics of inhibition of the low-Km mitochondrial aldehyde dehydrogenase were mixed. Mitochondria isolated from rats treated in vivo with diethyl maleate or phorone had a decreased capacity to oxidize either formaldehyde or acetaldehyde. The activity of the low-Km, but not the high-Km, mitochondrial aldehyde dehydrogenase was also inhibited. The production of CO2 plus formate from 0.2 mM-[14C]formaldehyde by isolated hepatocytes was only slightly inhibited (15-30%) by incubation with diethyl maleate or addition of cyanamide, suggesting oxidation primarily via formaldehyde dehydrogenase. However, the production of CO2 plus formate was increased 2.5-fold when the concentration of [14C]formaldehyde was raised to 1 mM. This increase in product formation at higher formaldehyde concentrations was much more sensitive to inhibition by diethyl maleate or cyanamide, suggesting an important contribution by mitochondrial aldehyde dehydrogenase. Thus diethyl maleate and phorone, besides depleting GSH, can also serve as effective inhibitors in vivo or in vitro of the low-Km mitochondrial aldehyde dehydrogenase. Inhibition of formaldehyde oxidation by these agents could be due to impairment of both enzyme systems known to be capable of oxidizing formaldehyde. It would appear that a critical amount of GSH, e.g. 90%, must be depleted before the activity of formaldehyde dehydrogenase becomes impaired.

Regulation of glucose production in rainbow trout: role of epinephrine in vivo and in isolated hepatocytes

2000 ◽  
Vol 278 (4) ◽  
pp. R956-R963 ◽  
Author(s):  
Jean-Michel Weber ◽  
Deena S. Shanghavi
Keyword(s):  
Rainbow Trout ◽  
Hepatic Glucose Production ◽  
Glucose Production ◽  
Isolated Hepatocytes ◽  
Relative Increase ◽  
Dependent Manner ◽  
Rainbow Trout Oncorhynchus Mykiss

The rate of hepatic glucose production (Ra glucose) of rainbow trout ( Oncorhynchus mykiss) was measured in vivo by continuous infusion of [6-3H]glucose and in vitro on isolated hepatocytes to examine the role of epinephrine (Epi) in its regulation. By elevating Epi concentration and/or blocking β-adrenoreceptors with propranolol (Prop), our goals were to investigate the mechanism for Epi-induced hyperglycemia to determine the possible role played by basal Epi concentration in maintaining resting Ra glucose and to assess indirect effects of Epi in the intact animal. In vivo infusion of Epi caused hyperglycemia (3.75 ± 0.16 to 8.75 ± 0.54 mM) and a twofold increase in Ra glucose (6.57 ± 0.79 to 13.30 ± 1.78 μmol ⋅ kg− 1 ⋅ min− 1, n = 7), whereas Prop infusion decreased Ra from 7.65 ± 0.92 to 4.10 ± 0.56 μmol ⋅ kg− 1 ⋅ min− 1( n = 10). Isolated hepatocytes increased glucose production when treated with Epi, and this response was abolished in the presence of Prop. We conclude that Epi-induced trout hyperglycemia is entirely caused by an increase in Ra glucose, because the decrease in the rate of glucose disappearance normally seen in mammals does not occur in trout. Basal circulating levels of Epi are involved in maintaining resting Ra glucose. Epi stimulates in vitro glucose production in a dose-dependent manner, and its effects are mainly mediated by β-adrenoreceptors. Isolated trout hepatocytes produce glucose at one-half the basal rate measured in vivo, even when diet, temperature, and body size are standardized, and basal circulating Epi is responsible for part of this discrepancy. The relative increase in Ra glucose after Epi stimulation is similar in vivo and in vitro, suggesting that indirect in vivo effects of Epi, such as changes in hepatic blood flow or in other circulating hormones, do not play an important role in the regulation of glucose production in trout.

scholarly journals Differential Regulation of Ferritin Subunits and Iron Transport Proteins: An Effect of Targeted Hepatic X-Irradiation

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Naila Naz ◽  
Shakil Ahmad ◽  
Silke Cameron ◽  
Federico Moriconi ◽  
Margret Rave-Fränk ◽  
...  
Keyword(s):  
Radiation Effects ◽  
Complete Blood Count ◽  
Mrna Level ◽  
Isolated Hepatocytes ◽  
Serum Marker ◽  
Neutrophil Granulocytes ◽  
Early Increase ◽  
Radiation Induced

The current study aimed to investigate radiation-induced regulation of iron proteins including ferritin subunits in rats. Rat livers were selectively irradiatedin vivoat 25 Gy. This dose can be used to model radiation effects to the liver without inducing overt radiation-induced liver disease. Sham-irradiated rats served as controls. Isolated hepatocytes were irradiated at 8 Gy. Ferritin light polypeptide (FTL) was detectable in the serum of sham-irradiated rats with an increase after irradiation. Liver irradiation increased hepatic protein expression of both ferritin subunits. A rather early increase (3 h) was observed for hepatic TfR1 and Fpn-1 followed by a decrease at 12 h. The increase in TfR2 persisted over the observed time. Parallel to the elevation of AST levels, a significant increase (24 h) in hepatic iron content was measured. Complete blood count analysis showed a significant decrease in leukocyte number with an early increase in neutrophil granulocytes and a decrease in lymphocytes.In vitro, a significant increase in ferritin subunits at mRNA level was detected after irradiation which was further induced with a combination treatment of irradiation and acute phase cytokine. Irradiation can directly alter the expression of ferritin subunits and this response can be strongly influenced by radiation-induced proinflammatory cytokines. FTL can be used as a serum marker for early phase radiation-induced liver damage.

scholarly journals Selective labelling and inactivation of creatine kinase isoenzymes by the thyroid hormone derivative N-bromoacetyl-3,3′,5-tri-iodo-l-thyronine

1993 ◽  
Vol 291 (2) ◽  
pp. 463-472 ◽  
Author(s):  
M Wyss ◽  
T Wallimann ◽  
J Köhrle
Keyword(s):  
Creatine Kinase ◽  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Rat Heart ◽  
Covalent Modification ◽  
Regulation Of Transcription ◽  
Selective Labelling ◽  
Mitochondrial Fractions

Besides their well-known regulation of transcription by binding to nuclear receptors, thyroid hormones have been suggested to have direct effects on mitochondria. In a previous study, incubation of rat heart mitochondria with 125I-labelled N-bromoacetyl-3,3′,5-tri-iodo-L-thyronine (BrAcT3), a thyroid hormone derivative with an alkylating side chain, resulted in the selective labelling of a protein doublet around M(r) 45,000 on SDS/polyacrylamide gels [Rasmussen, Köhrle, Rokos and Hesch (1989) FEBS Lett. 255, 385-390]. Now, this protein doublet has been identified as mitochondrial creatine kinase (Mi-CK). Immunoblotting experiments with the cytoplasmic and mitochondrial fractions of rat heart, brain and liver, as well as inactivation studies with the purified chicken CK isoenzymes have further demonstrated that all four CK isoenzymes (Mia-, Mib-, M- and B-CK) are indeed selectively labelled by BrAcT3. However, in contrast with their bromoalkyl derivatives, thyroid hormones themselves did not compete for CK labelling, suggesting that not the thyroid hormone moiety but rather the bromoacetyl-driven alkylation of the highly reactive ‘essential’ thiol group of CK accounts for this selective labelling. Therefore the assumption that CK isoenzymes are thyroid-hormone-binding proteins has to be dismissed. Instead, bromoacetyl-based reagents may allow a very specific covalent modification and inactivation of CK isoenzymes in vitro and in vivo.

Biodegradable Magnesium Implant: In Vivo and In Vitro Convergence

2014 ◽  
Author(s):  
Yeoheung Yun ◽  
Yongseok Jang ◽  
Juan Wang ◽  
Zhongyun Dong ◽  
Vesselin Shanov ◽  
...  
Keyword(s):  
Magnesium Alloys ◽  
Product Formation ◽  
In Vitro Test ◽  
Biodegradable Implant ◽  
Plasma Electrolyte ◽  
Vitro Test ◽  
Plasma Electrolyte Oxidation ◽  
Biodegradable Magnesium

In recent years, magnesium alloys have emerged as possible biodegradable implant material. A fundamental understanding of the nature of magnesium corrosion and the ability to control this process in vivo is critical to advancing the case for clinical use of magnesium based biomaterials. The biodegradation of magnesium is fundamentally linked to studies of its corrosion, which is dependent on the interfacing dynamics between the material and its environment. Thus, it is required to confirm what variable differentiate the corrosion behavior between in vitro and in vivo before optimizing and standardizing of in vitro test. This study was conducted to understand the biodegradation behavior of commercial AZ31 and Mg-Zn-Ca alloys with plasma electrolyte oxidation (PEO) under various biological environments using in vivo and in vitro testing methods mimicking in vivo physiological environment. This study is focused on the effect of Zn element concentration and PEO coating for magnesium alloys, and the correlation between the in vivo and in vitro in terms of corrosion rate, types of corrosion and corrosion product formation.

scholarly journals An in Vitro Model of Post-Exercise Hepatic Gluconeogenesis in the Gulf Toadfish Opsanus Beta

1989 ◽  
Vol 147 (1) ◽  
pp. 393-406 ◽  
Author(s):  
PATRICK J. WALSH
Keyword(s):  
Isolated Hepatocytes ◽  
Blood Parameters ◽  
Strenuous Exercise ◽  
Hepatic Gluconeogenesis ◽  
Post Exercise ◽  
Opsanus Beta ◽  
Stimulation Of ◽  
Gulf Toadfish

During strenuous exercise, fish develop substantial proton and lactate loads. Although acidosis is usually rapidly corrected during recovery (1–2 h), lactate levels often remain elevated for up to 8–12 h. The quantitative role of the liver in clearance of the lactate load during recovery from exercise in fish has received little direct examination. The purposes of this study were (1) to attempt to quantify hepatic contribution to lactate clearance, and (2) to identify factors that regulate hepatic gluconeogenesis during recovery from exercise in fish. Both in vivo and in vitro (isolated hepatocytes) approaches were used. Important blood parameters (pHe, Ccoco2, [lactate], [glucose], [epinephrine] and [norepinephrine]) were measured in the gulf toadfish (Opsanus beta Goode and Bean) during recovery from strenuous exercise, and they conformed to the general patterns for sluggish benthic species noted in earlier studies. When toadfish hepatocytes wereexposed to simulated post-exercise conditions in vitro, gluconeogenesis from lactate was stimulated by over 2.5-fold in ‘0–1 h-’ and ‘l-2h-post-exercise periods’. Variation of the extracellular parameters in controlled combinations indicated that exercise-induced changes in [glucose], [epinephrine], [norepinephrine], Pcoco2 and [HCO3−] had no significant effects on rates of gluconeogenesis.The observed stimulation of gluconeogenesis could be induced independently byeither decreased pH (which lowered Km for lactate) or increased [lactate] (bysimple hyperbolic kinetic effects), but the effects were not additive. Despite thispotentially adaptive stimulation of gluconeogenesis, I estimate, based on observedin vitro rates and in vivo estimates of lactate load, that hepatic gluconeogenesisaccounts for less than 2% of the lactate load clearance in toadfish.

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