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J V Castell

Publications and source records attributed to J V Castell.

115 records · Page 7Linked to original sources
PubMedDate not supplied

Functionality of cultured human hepatocytes from elective samples, cadaveric grafts and hepatectomies.

The major possible sources of human liver for hepatocyte isolation are elective liver biopsies, cadaveric liver grafts and therapeutic liver resections. The suitability in terms of metabolic-competent hepatocyte cultures and risk/benefit of these resources has been comparatively studied. To this end, viability of isolated hepatocytes, yield of isolation procedure, hepatocyte survival during culture and CYP activities were the parameters analysed. The best results were found in hepatocytes prepared from elective biopsies, whereas a marked reduction in viability and functional competence was seen in hepatocytes from hepatectomy samples. Metabolic differences were observed in total CYP oxidative metabolism (7-ethoxycoumarin O-deethylation, total testosterone hydroxylation), as well as in CYP3A4, CYP2C9 or CYP2C19 activities (testosterone oxidations at 6beta-, 16beta- and 17-positions, respectively). Vascular control during the hepatectomy procedure influenced hepatocyte functionality: higher CYP activities were found in hepatocytes isolated from samples obtained under non-ischemic conditions or continuous vascular clamping than in those obtained under intermittent vascular clamping. In addition to cellular functionality, other criteria such as sample availability or ethical aspects should be considered. Elective biopsies have low, but not absent, surgical risk. However, the better functionality and the higher accessibility of elective liver samples in comparison to the other groups suggest this source of liver tissue as the most appropriate for cell harvesting purposes.

Bayes Theorem↗
PubMedDate not supplied

The use of cultured hepatocytes to investigate the metabolism of drugs and mechanisms of drug hepatotoxicity.

Hepatotoxins can be classified as intrinsic when they exert their effects on all individuals in a dose-dependent manner, and as idiosyncratic when their effects are the consequence of an abnormal metabolism of the drug by susceptible individuals (metabolic idiosyncrasy) or of an immune-mediated injury to hepatocytes (allergic hepatitis). Some xenobiotics are electrophilic, and others are biotransformed by the liver into highly reactive metabolites that are usually more toxic than the parent compound. This activation process is the key to many hepatotoxic phenomena. Mitochondria are a frequent target of hepatotoxic drugs, and the alteration of their function has immediate effects on the energy balance of cells (depletion of ATP). Lipid peroxidation, oxidative stress, alteration of Ca(2+) homeostasis, and covalent binding to cell macromolecules are the molecular mechanisms that are frequently involved in the toxicity of xenobiotics. Against these potential hazards, cells have their own defence mechanisms (for example, glutathione, DNA repair, suicide inactivation). Ultimately, toxicity is the balance between bioactivation and detoxification, which determines whether a reactive metabolite elicits a toxic effect. The ultimate goal of in vitro experiments is to generate the type of scientific information needed to identify compounds that are potentially toxic to man. For this purpose, both the design of the experiments and the interpretation of the results are critical.]

Adenosine Triphosphate↗
PubMedDate not supplied

Effects of benorylate and impacina on the metabolism of cultured hepatocytes.

To directly evaluate the effects of benorylate and impacina on liver metabolism, we have adapted the use of cultured adult rat hepatocytes as a biological model. Cells were exposed to sub-toxic levels of the xenobiotic which were incorporated into the culture media. This was followed by the evaluation in treated cultures of some biochemical functions typical of the liver, namely, gluconeogenesis, glycogen metabolism, synthesis of plasma proteins and ureogenesis, and a comparison made with non-treated controls. Benorylate impaired glucose release by hepatocytes to the medium and net accumulation of glycogen was detected. Urea production also diminished (20%) in benorylate-treated cells. Impacina significantly increased the synthesis of albumin and tranferrin when added at therapeutic levels into the culture medium and did not alter other biochemical functions of the hepatocytes.

Animals↗
PubMedDate not supplied

Toxicity of paracetamol in human hepatocytes. Comparison of the protective effects of sulfhydryl compounds acting as glutathione precursors.

The hepatotoxicity of N-acetyl-p-aminophenol (acetaminophen, paracetamol) was investigated in hepatocyte cultures obtained from eight different human liver biopsies. Incubation of hepatocytes with paracetamol resulted in a dose- and time-dependent glutathione depletion. Glutathione decreased linearly for 8 h, reaching a minimum after 12 h of exposure. Cytotoxicity, assessed as loss of cellular protein from plates, was observed only when glutathione decreased below 20% for more than 12 h. However, in one donor, cytotoxicity was observed with even a moderate glutathione decrease. Prestimulation of hepatocytes with 1 mM phenobarbital or 2 microM methylcholanthrene for 48 h did not lead to a significant increase of paracetamol toxicity, although the glutathione levels in 3-methylcholanthrene-treated cells were somewhat lower. Several metabolic precursors were examined in vitro for their ability to increase intracellular glutathione and the results showed the following sequence: N-acetylcysteine greater than thioproline greater than cysteine greater than 2-oxo-4-thiazolidine carboxylic acid greater than methionine. However, only N-acetylcysteine, thioproline, and cysteine substantially increased glutathione levels when 1 mM paracetamol was present in the incubation medium and thus prevented its toxicity. N-acetylcysteine elevated glutathione even after 24 h of preexposure to paracetamol. The fact that cell damage did not correlate with glutathione levels in all human cultures suggests that glutathione depletion may not be the only determinant of paracetamol toxicity in human hepatocytes.

Acetaminophen↗
PubMedDate not supplied

Hepatotoxicity of the opioids morphine, heroin, meperidine, and methadone to cultured human hepatocytes.

Adult human hepatocytes in chemically defined culture conditions were incubated with morphine, heroin, meperidine, and methadone to investigate their potential hepatotoxicity to human liver. Cytotoxic effects were observed at about 100 times the plasma concentrations required to produce analgesia in human nonaddicts. Concentrations of 1 mM morphine, heroin, and meperidine reduced the glycogen content by 50%, while even 0.2 mM methadone produced a depletion of 70% after 24 h of treatment. Concentrations of 0.8 mM morphine and heroin, 0.4 mM meperidine, and 0.005 mM methadone inhibited the albumin synthesis by about 50% after 24 h of pretreatment. Intracellular glutathione was reduced to 50% of that of controls after 2-3 h of incubation with 2 mM morphine and 1 mM heroin, while 1 mM meperidine and 0.2 mM methadone produced a reduction of about 30% after 6 h incubation. The results show that therapeutic doses of the opioids is unlikely to produce irreversible damage to human hepatocytes, but opiate doses during tolerance or abuse may be a cause of liver dysfunction.

Cell Survival↗