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F L Martin

Publications and source records attributed to F L Martin.

28 records · Page 2Linked to original sources
PubMed1998

Comparison of paracetamol-induced hepatotoxicity in the rat in vivo with progression of cell injury in vitro in rat liver slices.

The flux in rat hepatic ratio of adenosine triphosphate levels to adenosine diphosphate levels (ATP/ADP) during the onset and progression of paracetamol-induced cell injury both in vivo and in vitro were investigated and compared. Leakage of lactate dehydrogenase (LDH) and potassium (K+), and mg water/mg dry weight quantified cell injury. ATP and ADP levels were determined using the luciferin-luciferase bioluminescence assay. For in vitro studies, liver slices obtained from phenobarbitone-induced rats were exposed to 10 mM paracetamol for 120 min (T0-T120) and, then incubated without paracetamol up to a further 240 min (T120-T360). For in vivo studies, groups of four phenobarbitone-induced rats received i.p. injections of 800 mg/kg paracetamol. ATP/ADP ratios fall upon exposure to paracetamol both in vitro and in vivo. However, unlike the in vitro situation where the fall in ATP/ADP ratios precedes and accompanies the progression of cell injury, the in vivo fall in ATP/ADP ratios is shown to occur as cell injury measurements begin to recover to control levels. However, despite these differences classic paracetamol-induced centrilobular necrosis is observed to occur both in vitro and in vivo. This study demonstrates that the liver slice model is a simple and useful technique to investigate the underlying mechanisms of paracetamol-induced cell injury.

Acetaminophen↗
PubMed1997

DNA damage in breast epithelial cells: detection by the single-cell gel (comet) assay and induction by human mammary lipid extracts.

The presence of DNA damage in primary cultures of human mammary epithelial cells (HMECs), and the ability of extracts of human mammary lipid to cause such damage, has been investigated. Lipid extracts, prepared by a solid-phase procedure, and HMECs were obtained from breast tissue removed from healthy women (ages 18-50 years) who were resident in the UK and undergoing elective reduction mammoplasties. DNA single strand breaks (SSBs) were detected using the single-cell gel assay (comet assay) with alkaline electrophoresis (pH 12.3) and quantified by measuring comet tail length (CTL) (microm). Untreated HMECs and HMECs incubated (30 min, 37 degrees C) with a mammary lipid extract, with or without DNA-repair inhibitors hydroxyurea (HU) and cytosine arabinoside (ara-C), were examined. Ionizing radiation was used as a positive control. An active lipid extract gave a linear dose-response over the range 2.0-12.2 g equivalents. When MCL-5 cells, a line of metabolically-competent human lymphoblastoid cells, were used to compare the DNA-damaging properties of lipid extracts from six different donors, significant interindividual variations (median CTLs were 15.0, 53.5, 32.5, <4.0, <4.0 and 77.5 microm respectively) were observed. In eight subjects, the donors' HMECs were examined both before and after treatment with extracts of that donor's own lipid. Pre-existing DNA damage was detected in untreated HMECs from some donors (median CTLs 22.0-37.5 microm) that was not present in others (median CTLs 4.0-11.5 microm), and increases in CTL could be induced by incubation with the matching lipid extract (8 g equivalent) in more than half (five out of eight) the subjects examined (median CTL up to 111.0 microm). There was a tendency for the most active lipid extracts to be those obtained from donors whose HMECs also contained the most pre-existing DNA SSBs. The results of this pilot study may prove to be significant in relation to the initiation of breast cancer.

Adult↗
PubMed1996

Genotoxicity of human mammary lipid.

We tested the proposition that human mammary lipid contains mutagenic/genotoxic agents that could cause DNA damage in adjacent epithelial cells. Lipid samples from breast tissue surgically removed from 40 women undergoing elective reduction mammoplasty were extracted by a solid-phase procedure. Mutagenicity was observed in Salmonella typhimurium TA98 and TA1538 in 16 of 40 (40%) extracts assayed with rat-liver S9, but not in its absence. No mutagenicity was seen in S. typhimurium TA100 or Escherichia coli WP2uvrA(pKM101). Bacterial mutagenicity correlated with micronucleus-forming activity in a metabolically competent mammalian cell line (MCL-5). This genotoxic activity merits further investigation in relation to the etiology of breast cancer.

Adipose Tissue↗
PubMed1996

Comparison of protection by fructose against paracetamol injury with protection by glucose and fructose-1,6-diphosphate.

We have compared the protective effect of fructose in normal Ringer solution during the onset and progression of cell injury induced by paracetamol in rat liver slices with the protective effect of glucose and fructose-1,6-diphosphate. Liver slices obtained from phenobarbitone-induced and non-induced rats were used in a model in vitro system. Slices were exposed to 10 mM paracetamol for 120 min and then incubated without paracetamol in the presence or absence of protective agents for a further 240 min. Cell injury was quantified by measuring leakage of lactate dehydrogenase (LDH) and potassium (K+). Adenosinetriphosphate (ATP) levels were measured using the luciferin-luciferase bioluminescence assay. Addition of higher concentrations of glucose (10-50 mM) to Ringer solution were not found to result in protection at the end of incubation in paracetamol-treated slices obtained from phenobarbitone-induced rats. Neither did sucrose nor mannitol protect. However, exclusion of glucose from Ringer solution resulted in cell injury in paracetamol-treated slices obtained from non-induced rats. Methionine, a known antidote for paracetamol poisoning, failed to protect in this instances but fructose did protect. This suggests that the presence of a glycolytic substrate plays a crucial role in cell protection. Further evidence for this is the finding that iodoacetate, an inhibitor of glycolysis, not only increase cell injury in paracetamol-treated slices but also reverses fructose protection. Fructose-1,6-diphosphate was found to protect against the onset and progression of cell injury in paracetamol-treated slices obtained from phenobarbitone induced rats. This protective agent is found to maintain high ATP levels and cell viability in paracetamol-treated slices at a time when paracetamol-treated slices show a profound loss of ATP levels and a significant increase in cell injury as measured by leakage of LDH and K+.

Acetaminophen↗
PubMed1996

Cell protection by fructose is independent of adenosine triphosphate (ATP) levels in paracetamol injury to rat liver slices.

Fructose protects cells against several types of injury but the mechanism of protection is uncertain. We have used paracetamol injury in rat liver slices as a model system to investigate the role of ATP levels in protection by fructose. Fructose depletes ATP levels in a concentration-dependent fashion in liver slices obtained from non-induced rats. Liver slices recover their ATP levels in the presence of fructose concentrations up to 10 mM. However, in the presence of of 20mM fructose, ATP levels are depleted for the duration of 240 min incubation. Adenine at 100 microM reverses the ATP depletion induced by 20 mM fructose in slices over 240 min incubation. Liver slices obtained from phenobarbitone induced rats were exposed to 10 mM paracetamol for 120 min and, then, incubated without paracetamol, with or without fructose for another 240 min. Introduction of 10 mM or 20 mM fructose in the second stage of incubation prevents paracetamol-induced injury. Fructose at 20 mM induces a rapid and marked depletion in slice ATP levels and these remain low throughout the second 240 min incubation period. Fructose at 10 mM maintains high ATP levels, even in paracetamol-treated slices. There is a profound protective effect against paracetamol-induced injury by either concentration. This suggests that protection is not dependent on high or on low ATP levels. Incubation of paracetamol-treated slices in the presence of 20 mM fructose plus 100 microM adenine in the second 240 min incubation period still results in the same level of protection as with 20 or 10 mM fructose along while reversing the ATP depletion observed with 20 mM fructose.

Acetaminophen↗
PubMed1995

Adenosine triphosphate (ATP) levels in paracetamol-induced cell injury in the rat in vivo and in vitro.

We have investigated the relationship between ATP levels and the onset and progression of cell injury induced by paracetamol overdose both in vivo and in vitro. Liver slices obtained from phenobarbitone-induced and non-induced rats were used in a model in vitro system. Slices were exposed to paracetamol (2-10 mM), for 120 min and then incubated without paracetamol for a further 240 min. ATP levels are reduced upon exposure to paracetamol in liver slices from both phenobarbitone-induced and non-induced rats. Cell injury, as quantified by measuring leakage of lactate dehydrogenase (LDH) and potassium (K+), does not become apparent until 240 min, some 120 min after exposure to paracetamol had ended. This irreversible cell injury is not observed in liver slices from non-induced rats. For in vivo studies rats were phenobarbitone-induced and received i.p. injections of 800 mg/kg body weight paracetamol. Hepatic ATP levels were measured and are found to drop sharply by 3 h post-injection. Development of irreversible hepatic cell injury was assessed by measuring serum enzyme (ALT) activity. ALT levels do not rise until 12 h have elapsed. Paracetamol in overdose gives rise to ATP depletion in liver cells, that is early, independent of paracetamol metabolism and probably spread throughout the lobule. In contrast cell injury is found late and only in our phenobarbitone-induced rats. No cell injury is observed in liver slices from non-induced rats. This suggests that while the level of ATP depletion which is observed may be a necessary part of cell injury by paracetamol, it is not a sufficient cause.

Acetaminophen↗