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Title: Role of gamma-glutamyltransferase in putrescine uptake by rat type II pneumocytes
Authors: van Klaveren, R J ×
Hoet, Peter
Demedts, Maurice
Nemery, Benoit #
Issue Date: Sep-1995
Publisher: Pergamon-elsevier science ltd
Series Title: Biochemical Pharmacology vol:50 issue:7 pages:981-9
Abstract: Putrescine uptake in type II pneumocytes is a carrier-mediated active process. Our hypothesis was that oligoamines might be taken up into the cell at least in part by gamma-glutamyltransferase (gamma-GT). This was investigated in rat type II pneumocytes 24 hr after their isolation. Preexposure to 125 microM L-buthionine-[SR]-sulfoximine (BSO) or 100 microM diethylmaleate (DEM), both of which affect intracellular glutathione (GSH) only, were found to decrease GSH by 85% (p < 0.05) and 62%, respectively (p < 0.05), without change in [3H]-putrescine uptake. Preexposure to 20 microM N-ethylmaleimide (NEM), which affects intra- and extracellular GSH, decreased intracellular GSH by 79% (p = 0.015) and putrescine uptake by 39% (p = 0.03). Selective extracellular GSH depletion by 10 microM copper-o-phenanthroline complex (CuP) led to a decrease in putrescine uptake of 41% (p = 0.001), while intracellular GSH remained unchanged. Specific inhibition of gamma-GT by 5-20 mM serine-borate or 5 mM acivicin gave similar degrees of putrescine uptake inhibition (39.5% and 40.5%). The kinetic properties of the putrescine uptake system in the presence of acivicin and serine-borate indicated that the Vmax decreased by 25%, while Km remained unchanged. In experiments with pure gamma-GT, the oligoamines putrescine, spermidine and spermine, and cystamine proved to be acceptor substrates for gamma-GT, all having similar efficiencies (Vmax/Km); methylglyoxal-bis-(guanyl-hydrazone) and paraquat were not accepted. As extracellular GSH is required for gamma-GT, and because its extracellular depletion inhibits putrescine uptake as much as specific inhibition of gamma-GT, we suggest that 30-40% of the putrescine uptake in type II pneumocytes occurs by gamma-GT and that, therefore, at least two systems are involved in the uptake of putrescine.
ISSN: 0006-2952
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Pneumology
Environment and Health - miscellaneous
Occupational, Environmental and Insurance Medicine (-)
× corresponding author
# (joint) last author

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