Effects of Ammonia Exposition on Glioma Cells: Changes in Cell Volume and Organic Osmolytes Studied by Diffusion-Weighted and High-Resolution NMR Spectroscopy

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Abstract
NH4Cl (10 mM) caused a sustained increase in the cell volume in immobilized, perfused F98 glioma cells to approx. 125% of control after 3 h, as measured by diffusion-weighted 1H NMR spectroscopy. Concomitantly, the glutamine (Gln) concentration increased by 130%, accompanied by a marked decrease in cytosolic osmolytes, i.e. myo-inositol and taurine, determined from 1H NMR spectra of PCA extracts. Inhibition of Gln synthetase partially prevented the increase in water content. While losses of organic osmolytes are also observed under hypotonic conditions, the rapid cell swelling is followed by the regulatory cell volume decrease (RVD), and is accompanied by decreased cytosolic Gln. We suggest that the rise in intracellular osmolarity, which is attributed to NH4Cl metabolism to Gln, but also to alanine (Ala), is not compensated by the release of other osmolytes, and causes cell swelling without RVD.

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