Increase in gamma-glutamyltransferase by glutathione depletion in rat type II pneumocytes.
The purpose of our study was to investigate the effect of oxidative stress or intracellular glutathione (GSH) depletion on gamma-glutamyltransferase (gamma-GT) activity in cultured type II pneumocytes. Twenty-four hours after isolation, primary cultures of rat type II pneumocytes were preincubated with one of four compounds: 15, 30, 60, 125, 250 microM L-buthionine-[SR]-sulfoximine (BSO) for 3 h; 100, 200, 400, 800 microM tertiary-butylhydroperoxide (t-BOOH) for 45 min; 10, 25, 50, 100 microM menadione for 15 min; 100, 1000 microM paraquat for 1 h. GSH levels, H2O2 and O2.- generation were measured immediately after the incubation, gamma-GT activity and GSH levels also up to 24 h or 48 h later. Exposure to BSO led to a persistent GSH depletion without increase in H2O2 or O2.- production, together with a dose and time-dependent increase (doubling) of gamma-GT activity with a nonsignificant increase in gamma-GT mRNA expression 24 h after exposure to BSO. Exposure to 100 microM menadione, which increased H2O2 production, decreased gamma-GT activity. t-BOOH or paraquat did not give rise to a measurable increase in H2O2 or O2.-. Paraquat did not affect initial GSH levels, but increased GSH and decreased gamma-GT activity 24 h later. t-BOOH (400 and 800 microM) initially decreased GSH, and tended to increase GSH 24 h later, 100 and 200 microM increased gamma-GT activity 24 h later, but 800 microM decreased it. Restoration of intracellular GSH levels by addition of GSH to the culture medium completely prevented the increase in gamma-GT activity by BSO, while the addition of catalase or DMTU had no effect. We conclude that at least two effects are operating upon gamma-GT activity: GSH depletion seems to increase gamma-GT activity, while exposure to compounds generating oxidative stress correlates with a decrease in gamma-GT activity.
van Klaveren
R J
RJ
Laboratory of Pneumology, K.U. Leuven, Belgium.
Hoet
P H
PH
Pype
J L
JL
Demedts
M
M
Nemery
B
B
D000818:Animals; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008168:Lung / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D018384:Oxidative Stress; D010269:Paraquat / Q000008:administration & dosage / Q000494:pharmacology; D010545:Peroxides / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism; D014812:Vitamin K / Q000008:administration & dosage / Q000494:pharmacology; D005723:gamma-Glutamyltransferase / Q000378:metabolism*; D020122:tert-Butylhydroperoxide
D010545:Peroxides; D017382:Reactive Oxygen Species; D013481:Superoxides; D014812:Vitamin K; D019328:Buthionine Sulfoximine; D020122:tert-Butylhydroperoxide; D006861:Hydrogen Peroxide; D005723:gamma-Glutamyltransferase; D005978:Glutathione; D010269:Paraquat