Ammonium-induced calcium mobilization in 1321N1 astrocytoma cells

Journal Article · Fri Feb 15 04:00:00 EST 2008 · Toxicology and Applied Pharmacology

DOI:https://doi.org/10.1016/j.taap.2007.10.012· OSTI ID:21077919

Hillmann, Petra; Koese, Meryem; Soehl, Kristina ^[1]

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1. Pharmaceutical Sciences Bonn (PSB), Pharmaceutical Chemistry I, Pharmaceutical Institute, University of Bonn, Bonn (Germany)

High blood levels of ammonium/ammonia (NH{sub 4}{sup +}/NH{sub 3}) are associated with severe neurotoxicity as observed in hepatic encephalopathy (HE). Astrocytes are the main targets of ammonium toxicity, while neuronal cells are less vulnerable. In the present study, an astrocytoma cell line 1321N1 and a neuroblastoma glioma hybrid cell line NG108-15 were used as model systems for astrocytes and neuronal cells, respectively. Ammonium salts evoked a transient increase in intracellular calcium concentrations ([Ca{sup 2+}]{sub i}) in astrocytoma (EC{sub 50} = 6.38 mM), but not in NG108-15 cells. The ammonium-induced increase in [Ca{sup 2+}]{sub i} was due to an intracellular effect of NH{sub 4}{sup +}/NH{sub 3} and was independent of extracellular calcium. Acetate completely inhibited the ammonium effect. Ammonium potently reduced calcium signaling by G{sub q} protein-coupled receptors (H{sub 1} and M3) expressed on the cells. Ammonium (5 mM) also significantly inhibited the proliferation of 1321N1 astrocytoma cells. While mRNA for the mammalian ammonium transporters RhBG and RhCG could not be detected in 1321N1 astrocytoma cells, both transporters were expressed in NG108-15 cells. RhBG and RhBC in brain may promote the excretion of NH{sub 3}/NH{sub 4}{sup +} from neuronal cells. Cellular uptake of NH{sub 4}{sup +}/NH{sub 3} was mainly by passive diffusion of NH{sub 3}. Human 1321N1 astrocytoma cells appear to be an excellent, easily accessible human model for studying HE, which can substitute animal studies, while NG108-15 cells may be useful for investigating the role of the recently discovered Rhesus family type ammonium transporters in neuronal cells. Our findings may contribute to the understanding of pathologic ammonium effects in different brain cells, and to the treatment of hyperammonemia.

• OSTI ID: 21077919
• Journal Information: Toxicology and Applied Pharmacology, Journal Name: Toxicology and Applied Pharmacology Journal Issue: 1 Vol. 227; ISSN TXAPA9; ISSN 0041-008X
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
ACETATES
AMMONIA
BLOOD
BRAIN
CALCIUM
CALCIUM IONS
EXCRETION
GLIOMAS
LIVER
RECEPTORS
TOXICITY