Biomedical subjects

C Domenicotti

Publications and source records attributed to C Domenicotti.

25 records · Page 2Linked to original sources

PubMed1994

Impairment of lipoglycoprotein metabolism in rat liver cells induced by 1,2-dichloroethane.

BACKGROUND: 1,2-Dichloroethane (DCE) is a volatile liquid readily absorbed through dermal, digestive, or inhalatory routes. After inhalation or oral administration to rats, death occurs within a narrow range of concentrations (six hour LC50 = 5100 mg/m3). Exposure to single high doses of DCE resulted in adverse effects on the central nervous system, liver, kidneys, adrenals, and lungs. The liver showed fatty changes and hepatocellular necrosis with haemorrhage. These injuries are probably related to changes in several cell functions and constituents. Therefore, it was decided to investigate whether DCE was capable of impairing the secretion of hepatocellular lipoglycoproteins acting both at the level of the Golgi apparatus and endoplasmic reticulum. METHODS: Isolated hepatocytes of Wistar rats were prelabelled with two precursors of lipoglycoproteins 3H-Na-palmitate and 14C-glucosamine, and then exposed to concentrations of DCE from mean (SD) 4.4 (0.03) to 6.5 (0.02) mM for different durations ranging from five to 60 minutes. To measure lipid and sugar bound radioactivity, a preliminary separation of cell homogenate, cytosol, total microsomes, Golgi apparatus, and lipoglycoproteins secreted into cell suspension medium was carried out. RESULTS: After five minutes of exposure, DCE did not induce obvious changes in cell viability or lactic dehydrogenase leakage, but a significant (p < 0.01) depletion of reduced glutathione content was seen (40.10 (4.3) nM/10(6) cells). Furthermore, the cells poisoned by DCE started to show noticeable accumulation of 3H-Na-palmitate in the Golgi apparatus after five minutes (5103 (223) dpm/10(6) cells) and in the microsomes after 15 minutes (85,470 (7190) dpm/10(6) cells). There was a simultaneous significant increase in 14C-glucosamine content in the Golgi apparatus (690 (55) dpm/10(6) cells) and the microsomes (15,975 (2035) dpm/10(6) cells). The specific radioactivity of lipid and sugar moieties incorporated in secreted lipoglycoproteins was already significantly reduced after only five minutes of exposure (480 (57) dpm/10(6) cells for lipids, and 315 (45) dpm/10(6) cells for sugars). CONCLUSIONS: Overall, DCE, like other haloalkanes, produces a block of secretion of hepatocellular lipoglycoproteins as early as five minutes after poisoning. The simultaneous percentage increases into Golgi apparatus and microsomes of lipid and sugar bound radioactivity suggest that lipid retention at the sites of processing of lipoglycoproteins would probably play an important part in the early stages of cellular accumulation of fat after exposure to DCE.

Animals↗

PubMed1993

Modulation of rat liver protein kinase C during "in vivo" CC14-induced oxidative stress.

Rat intoxication with a single dose of the hepatotoxin carbon tetrachloride induces a significant modification of liver protein kinase C total activity which depends on the degree of the intrahepatocyte oxidative unbalance provoked by various concentrations of the haloalkane. Low carbon tetrachloride amounts stimulate total protein kinase C activity, while one order of magnitude higher amounts exert strong enzyme inhibition. The latter effect is due to an early inactivation followed with progress of time by a proteolytic degradation of the enzyme. A pathological recruitment of the calcium-dependent protein kinase C regulatory enzymes calpain and calpastatin appears responsible for protein kinase C loss. The prolonged excess of cytosolic calcium which characterizes the single high dose carbon tetrachloride poisoning also leads to inactivation of calpain II and calpastatin in a time-dependent manner.

Animals↗

PubMed1993

[Changes in lipoglycoprotein metabolism in toxic fatty liver].

BACKGROUND: A number of agents that produce liver injury also cause the accumulation of an abnormal amount of fat, predominantly triglycerides (TGs) in the parenchymal cells. Fatty liver (FL) is the result of an hepatocyte imbalance between the rate of synthesis and output of TGs into the plasma. TGs are not secreted as such, but combined with a glycoprotein moiety, and particularly with the very low density lipoproteins (VLDLs). This fraction is involved in the transport of hepatic TGs to extrahepatic tissues. FL can be induced by either acute or chronic administration of ethanol (EtOH), and/or several haloalkanes (carbon tetrachloride, CCl4; 1.2-dichloroethane, DCE; 1.1.2.2-tetrachloroethane, TTCE), both in laboratory animals and in man. Since the pathogenesis of this disease is a crucial problem, as yet undefined, the purpose of this article is to summarize the studies which have unraveled some of the mechanisms involved in FL, particularly the role played by impaired lipoglycoproteins (LGP) metabolism in rat liver. DISCUSSION: An important element in the pathogenesis of EtOH- and haloalkanes-induced FL is the impairment of hepatic secretion of VLDLs, which occurs soon after poisoning. Various steps of the secretory pathway are probably involved in the expression of such damage. The intoxication of rats with these xenobiotics leads to an early impairment of the hepatocyte system responsible for terminal glycosylation and maturation of LGP at the level of three different subfractions (F1, F2 and F3) of purified Golgi apparatus (GA). The earliest functional change is a block of LGP transit through the GA cisternae and vesicles, both in isolated hepatocyte model and in the whole animal. The glycosylation of LGP is a multistep process which starts in the rough endoplasmic reticulum (RER), and comes to its end in the GA. Dolichols (Dol) are a family of long-chain polyisoprenoid alcohols, present either as neutral free-Dol and dolichyl-phosphate (Dol-P). The latter acts as a glycosyl carrier across the RER membranes in the initial steps of LGP biosynthesis. Nearly all the other reactions occur in GA, where free-Dol have a role either in terminal LGP processing or in their secretion into the blood stream. Several investigations indicated that both EtOH and haloalkanes (CCl4, DCE, and TTCE) may selectively and precociously impair the total microsomes (TM) and GA pool of Dol, particularly in F1. Lipid peroxidation appears to be the fundamental mechanism involved. CONCLUSIONS: Such results, obtained in several works, point out a key role played in FL by selective impairment of MT and GA processes which provide for the synthesis, maturation and release of hepatic LGP.

Animals↗

PubMed1993

Acetaldehyde-induced impairment of protein glycosylation in liver Golgi apparatus.

The effects of acute ethanol intoxication on the glycoprotein metabolism of rat liver Golgi apparatus have been investigated. A marked reduction of the galactosyltransferase and sialyltransferase activities was observed in Golgi membranes 6 h after ethanol administration (6g/Kg body wt) together with the retention of glycoproteins in the hepatocyte. Methylpyrazole, an inhibitor of alcohol dehydrogenase, administrated "in vivo" (10 mg/Kg body wt) prevented the ethanol-induced inhibition of both the transferase activities. Acetaldehyde formed "in vitro" unstable and stable adducts with Golgi membrane proteins and with purified galactosyltransferase. These results suggest that the impairment of glycoprotein metabolism at the level of liver Golgi apparatus may be mediated, at least in part, through the acetaldehyde formation during ethanol oxidation.

Acetaldehyde↗

PubMed1990

Inactivation of hepatocyte protein kinase C by carbon tetrachloride: involvement of drug's metabolic activation and prooxidant effect.

The involvement of CCl4 biotransformation mechanism in decreasing the Protein Kinase C activity has been analyzed in hepatocytes isolated from phenobarbital-pretreated rats. A significant inhibition (55%) and an almost total disappearance (87%) of the enzyme activity were observed at 15 min and at 30 min incubation with CCl4, respectively. Cell preincubation with Trolox or desferrioxamine allowed a marked whilst not complete protection of both cytosolic and particulate Protein Kinase C activity. These results show that the CCl4 reactive metabolites play a primary role in hepatocyte Protein Kinase C impairment and suggest that besides lipid peroxidation other mechanisms -possibly a derangement of Ca2+ homeostasis- may be involved in this process.

Animals↗

PubMed1990

Effects of CCl4 poisoning on metabolism of dolichol in rat liver microsomes and Golgi apparatus.

Carbon tetrachloride (CCl4) poisoning affects glycoprotein processing and maturation at the level of rat liver microsomes and Golgi apparatus. HPLC analysis showed that within 5-60 min after CCl4 administration the levels of total dolichol, free dolichol and dolichyl-phosphate strongly decreased both in total microsomes and in Golgi apparatus. The most marked and early reduction of total dolichol was observed in the secretory membranes of Golgi area already 15 min after CCl4 poisoning. The incubation of CCl4-pretreated isolated hepatocytes with [3H]-mevalonate showed a significant slowing down of the label incorporation into both free-dolichol and dolichyl-phosphate. Moreover, lipid peroxidation might cause alterations in the molecular structure of both free-dolichol and dolichyl-phosphate. A notable prevention of dolichol decrease was observed in animals pretreated with vitamin E. The results suggest that the prooxidant activity of CCl4 is able to affect the metabolism of dolichol either by increasing the oxidative degradation or impairing the biosynthetic pathway.

Animals↗

PubMedDate not supplied

[Toxicity of 4-chloro-2-nitroaniline and 2-chloro-4-nitroaniline to isolated rat hepatocytes].

The toxicity of 4-chloro-2-nitroaniline (4C2NA) and 2-chloro-4-nitroaniline (2C4NA) was investigated on isolated rat hepatocytes following 1-3 hours of exposure to 0.2 and/or 2 mM of these xenobiotics. The higher of the two concentrations appeared to induce a statistically significant loss of cellular viability (p less than 0.01 compared to control), judged by Trypan Blue staining, after 3 hours of incubation with these substances means = 58, SD = 7%; and means = SD = 7%; for 4C2NA and 2C4NA, respectively). Furthermore, both chloronitroanilines produced an hepatocellular and microsomal damage demonstrated by conspicuous changes in LDH and G-6-Pase activities (p less than 0.01). The exposure to 2 mM of both 4C2NA and/or 2C4NA produced a marked depletion of the intracellular pool of GSH after 3 hours (13 mM/10(6) and 10 mM/10(6) cells, respectively; p less than 0.01). Thus it seems possible that 2C4NA may induce a more severe cellular damage than that induced by 4C2NA.

Aniline Compounds↗