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Changes in the ornithine cycle following ionising radiation cause a cytotoxic conditioning of the culture medium of H35 hepatoma cells.

van Rijn J, van den Berg J, Teerlink T, Kruyt FA, Schor DS, Renardel de Lavalette AC, van den Berg TK, Jakobs C, Slotman BJ - Br. J. Cancer (2003)

Bottom Line: A strong decrease in medium arginine is accompanied with parallel increases in ornithine, citrulline and ammonia.Development of cytotoxicity by irradiated cells is completely prevented with the arginase inhibitor L-norvaline, in arginine-deficient medium or when citrulline replaces arginine.These preventive measures result in subtoxic ammonia levels.

View Article: PubMed Central - PubMed

Affiliation: Radiation Oncology, VU Medical Center, Amsterdam, The Netherlands. j.vanrijn@vumc.nl

ABSTRACT
Cultured H35 hepatoma cells release a cytotoxic factor in response to irradiation with X-rays. When the conditioned medium from irradiated cells is given to nonirradiated cells, growth is inhibited and followed by cell death, possibly apoptosis, Analysis of the conditioned medium reveals a dramatic change in the ornithine (urea) cycle components after the irradiation. A strong decrease in medium arginine is accompanied with parallel increases in ornithine, citrulline and ammonia. The high level of ammonia appears to be largely responsible for the observed cytotoxicity. The development of hyperammonia by irradiated cells and the related toxicity depend on the radiation dose and the number of cells seeded thereafter for the medium conditioning. Development of cytotoxicity by irradiated cells is completely prevented with the arginase inhibitor L-norvaline, in arginine-deficient medium or when citrulline replaces arginine. These preventive measures result in subtoxic ammonia levels.

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Related in: MedlinePlus

Effect of ammonium chloride on cell proliferation. Cells were incubated in fresh medium with various amounts of NH4Cl and counted after an incubation of 72 h. Except for the highest two concentrations with values of 0.6 and 0.5, respectively, the cloning efficiency was not affected.
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fig7: Effect of ammonium chloride on cell proliferation. Cells were incubated in fresh medium with various amounts of NH4Cl and counted after an incubation of 72 h. Except for the highest two concentrations with values of 0.6 and 0.5, respectively, the cloning efficiency was not affected.

Mentions: To investigate whether the changes in the ornithine cycle composition of CMX are related to the cytotoxic effect, a number of tests were done. The addition of 2–4 mM arginine to the arginine-depleted CMX does not abrogate its cytotoxicity. Neither ornithine nor citrulline is cytotoxic in normal cultures at concentrations of 1–2 mM (results not shown). However, the increase in ammonia appears to be critical. When H35 cells are exposed to increasing concentrations of ammonium chloride for 72 h, an increasing growth inhibition is noticed from about 2 mM NH4+ (Figure 7Figure 7


Changes in the ornithine cycle following ionising radiation cause a cytotoxic conditioning of the culture medium of H35 hepatoma cells.

van Rijn J, van den Berg J, Teerlink T, Kruyt FA, Schor DS, Renardel de Lavalette AC, van den Berg TK, Jakobs C, Slotman BJ - Br. J. Cancer (2003)

Effect of ammonium chloride on cell proliferation. Cells were incubated in fresh medium with various amounts of NH4Cl and counted after an incubation of 72 h. Except for the highest two concentrations with values of 0.6 and 0.5, respectively, the cloning efficiency was not affected.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2747531&req=5

fig7: Effect of ammonium chloride on cell proliferation. Cells were incubated in fresh medium with various amounts of NH4Cl and counted after an incubation of 72 h. Except for the highest two concentrations with values of 0.6 and 0.5, respectively, the cloning efficiency was not affected.
Mentions: To investigate whether the changes in the ornithine cycle composition of CMX are related to the cytotoxic effect, a number of tests were done. The addition of 2–4 mM arginine to the arginine-depleted CMX does not abrogate its cytotoxicity. Neither ornithine nor citrulline is cytotoxic in normal cultures at concentrations of 1–2 mM (results not shown). However, the increase in ammonia appears to be critical. When H35 cells are exposed to increasing concentrations of ammonium chloride for 72 h, an increasing growth inhibition is noticed from about 2 mM NH4+ (Figure 7Figure 7

Bottom Line: A strong decrease in medium arginine is accompanied with parallel increases in ornithine, citrulline and ammonia.Development of cytotoxicity by irradiated cells is completely prevented with the arginase inhibitor L-norvaline, in arginine-deficient medium or when citrulline replaces arginine.These preventive measures result in subtoxic ammonia levels.

View Article: PubMed Central - PubMed

Affiliation: Radiation Oncology, VU Medical Center, Amsterdam, The Netherlands. j.vanrijn@vumc.nl

ABSTRACT
Cultured H35 hepatoma cells release a cytotoxic factor in response to irradiation with X-rays. When the conditioned medium from irradiated cells is given to nonirradiated cells, growth is inhibited and followed by cell death, possibly apoptosis, Analysis of the conditioned medium reveals a dramatic change in the ornithine (urea) cycle components after the irradiation. A strong decrease in medium arginine is accompanied with parallel increases in ornithine, citrulline and ammonia. The high level of ammonia appears to be largely responsible for the observed cytotoxicity. The development of hyperammonia by irradiated cells and the related toxicity depend on the radiation dose and the number of cells seeded thereafter for the medium conditioning. Development of cytotoxicity by irradiated cells is completely prevented with the arginase inhibitor L-norvaline, in arginine-deficient medium or when citrulline replaces arginine. These preventive measures result in subtoxic ammonia levels.

Show MeSH
Related in: MedlinePlus