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Ammonia production by IMR-90 fibroblast cultures: effects of ammonia on glutathione, gamma-glutamyl transpeptidase, lysosomal enzymes, and cell division.

Abstract：

:gamma-Glutamyl transpeptidase has multi-catalytic activities. It degrades glutathione and can produce ammonia from glutamine. The present study was designed to examine whether the decreased cell proliferation, cellular glutathione content and concurrent increase in ammonia production in senescent cells in culture are the result of increased gamma-glutamyl transpeptidase activity. We used IMR-90 fibroblast and 3T3 LI preadipocyte cultures. The cellular glutathione content depended upon cell proliferation and cell density. The glutathione content was higher in cells at logarithmic growth, and lower at stationary growth or post confluency; dead cells had no detectable glutathione by the method currently used. The glutathione content was minimal in "old" IMR-90 cells, regardless of cell density. On the other hand, an increase occurred in the unit number of molecules of bound 5-iodoacetoamidofluorescein, an active-site directed stoichiometric inhibitor of transpeptidase. That result corresponded favorably with the increased enzyme activity, suggesting that the number of enzyme molecules per cell was increased. The inhibition of ammonia production of the cultures by inhibition of gamma-glutamyl transpeptidase by 5-iodoacetoamidofluorescein and reversible inhibition of ammonia production by a serine-borate mixture were consistent with our postulate. Addition of NH4Cl (0.1 mM) to IMR-90 cultures caused increased activities of transpeptidase and some of the lysosomal enzymes; concurrently, the amount of cellular glutathione and the number of cell divisions decreased. This suggests that the increased ammonia production presumably resulting from glutaminase activity of the observed increase of transpeptidase may profoundly affect certain cellular functions.

journal_name

J Cell Physiol

journal_title

Journal of cellular physiology

authors

Takahashi S,Nakagawa S,Zeydel M,Bhargava G

doi

10.1002/jcp.1041250114

subject

Has Abstract

pub_date

1985-10-01 00:00:00

pages

107-14

issue

eissn

0021-9541

issn

1097-4652

journal_volume

125

pub_type

杂志文章

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Ammonia production by IMR-90 fibroblast cultures: effects of ammonia on glutathione, gamma-glutamyl transpeptidase, lysosomal enzymes, and cell division.