Tags

Type your tag names separated by a space and hit enter

Decrease in gamma-glutamyltransferase activity in rat type II cells exposed in vitro to hyperoxia: effects of the 21-aminosteroid U-74389G.
Exp Lung Res. 1997 Jul-Aug; 23(4):347-59.EL

Abstract

Although the effect of hyperoxia on antioxidant enzymes is well known, the effect of subtoxic levels of hyperoxia on gamma-glutamyltransferase (gamma-GT), involved in the degradation and uptake of extracellular GSH for intracellular GSH synthesis, is unknown. The aim of the study was to investigate (1) the effects of in vitro hyperoxia on gamma-GT activity of type II cells and (2) the effects of the lazaroid U-74389G and N-acetylcysteine (NAC) on the hyperoxia-induced changes in gamma-GT and antioxidant enzyme activities. At 48 h after isolation, rat type II cells were exposed for 2 days to air, 60% O2 or 85% O2 with or without 30 microM U-74389G or 100 microM NAC. After the exposure, the cells were harvested and assayed for superoxide dismutase (SOD), glutathione peroxidase (GPx), gamma-GT activity, and GSH levels. In another series of experiments 85% O2-exposed cells, with or without U-74389G, were used for Northern blotting of gamma-GT mRNA. Exposure to 60% O2 decreased gamma-GT and GSH by -47 and -34%, respectively, while SOD and GPx activities remained unchanged. After 85% O2-exposure gamma-GT decreased by -55%, SOD and GPx increased by +55 and +87%, respectively, while GSH decreased by -35%. NAC treatment decreased gamma-GT activity by -42% in the air-exposed cells. After 60% O2, U-74389G led to significantly higher gamma-GT (+117%) and GSH (+26%) while NAC only led to higher GSH (+28%) compared to the oxygen-exposed cells not treated with NAC or U-74389G. After 85% O2 U-74389G increased gamma-GT, SOD, and GSH by +72, +58, and +68%, respectively, while NAC only increased SOD (+49%) and GSH (+26%) compared to the oxygen-exposed cells not treated with NAC or U-74389G. The 85% O2 exposure, with or without U-74389G, had no effect on gamma-GT mRNA levels. The results show that hyperoxia decreases rat type II cell gamma-GT activity in vitro. This effect was not related to an altered regulation at mRNA level and it was not associated with the hyperoxia-induced decrease in intracellular GSH, since restoration of the GSH levels by NAC did not restore gamma-GT activity. The lazaroid U-74389G with vitamin E-like properties effectively prevented the decrease in gamma-GT and GSH, so that direct inactivation of the membrane-bound gamma-GT by hyperoxia is the most likely mechanism.

Authors+Show Affiliations

Laboratory of Pneumology, K.U. Leuven, Belgium.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

9202959

Citation

van Klaveren, R J., et al. "Decrease in Gamma-glutamyltransferase Activity in Rat Type II Cells Exposed in Vitro to Hyperoxia: Effects of the 21-aminosteroid U-74389G." Experimental Lung Research, vol. 23, no. 4, 1997, pp. 347-59.
van Klaveren RJ, Pype JL, Demedts M, et al. Decrease in gamma-glutamyltransferase activity in rat type II cells exposed in vitro to hyperoxia: effects of the 21-aminosteroid U-74389G. Exp Lung Res. 1997;23(4):347-59.
van Klaveren, R. J., Pype, J. L., Demedts, M., & Nemery, B. (1997). Decrease in gamma-glutamyltransferase activity in rat type II cells exposed in vitro to hyperoxia: effects of the 21-aminosteroid U-74389G. Experimental Lung Research, 23(4), 347-59.
van Klaveren RJ, et al. Decrease in Gamma-glutamyltransferase Activity in Rat Type II Cells Exposed in Vitro to Hyperoxia: Effects of the 21-aminosteroid U-74389G. Exp Lung Res. 1997;23(4):347-59. PubMed PMID: 9202959.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Decrease in gamma-glutamyltransferase activity in rat type II cells exposed in vitro to hyperoxia: effects of the 21-aminosteroid U-74389G. AU - van Klaveren,R J, AU - Pype,J L, AU - Demedts,M, AU - Nemery,B, PY - 1997/7/1/pubmed PY - 1997/7/1/medline PY - 1997/7/1/entrez SP - 347 EP - 59 JF - Experimental lung research JO - Exp. Lung Res. VL - 23 IS - 4 N2 - Although the effect of hyperoxia on antioxidant enzymes is well known, the effect of subtoxic levels of hyperoxia on gamma-glutamyltransferase (gamma-GT), involved in the degradation and uptake of extracellular GSH for intracellular GSH synthesis, is unknown. The aim of the study was to investigate (1) the effects of in vitro hyperoxia on gamma-GT activity of type II cells and (2) the effects of the lazaroid U-74389G and N-acetylcysteine (NAC) on the hyperoxia-induced changes in gamma-GT and antioxidant enzyme activities. At 48 h after isolation, rat type II cells were exposed for 2 days to air, 60% O2 or 85% O2 with or without 30 microM U-74389G or 100 microM NAC. After the exposure, the cells were harvested and assayed for superoxide dismutase (SOD), glutathione peroxidase (GPx), gamma-GT activity, and GSH levels. In another series of experiments 85% O2-exposed cells, with or without U-74389G, were used for Northern blotting of gamma-GT mRNA. Exposure to 60% O2 decreased gamma-GT and GSH by -47 and -34%, respectively, while SOD and GPx activities remained unchanged. After 85% O2-exposure gamma-GT decreased by -55%, SOD and GPx increased by +55 and +87%, respectively, while GSH decreased by -35%. NAC treatment decreased gamma-GT activity by -42% in the air-exposed cells. After 60% O2, U-74389G led to significantly higher gamma-GT (+117%) and GSH (+26%) while NAC only led to higher GSH (+28%) compared to the oxygen-exposed cells not treated with NAC or U-74389G. After 85% O2 U-74389G increased gamma-GT, SOD, and GSH by +72, +58, and +68%, respectively, while NAC only increased SOD (+49%) and GSH (+26%) compared to the oxygen-exposed cells not treated with NAC or U-74389G. The 85% O2 exposure, with or without U-74389G, had no effect on gamma-GT mRNA levels. The results show that hyperoxia decreases rat type II cell gamma-GT activity in vitro. This effect was not related to an altered regulation at mRNA level and it was not associated with the hyperoxia-induced decrease in intracellular GSH, since restoration of the GSH levels by NAC did not restore gamma-GT activity. The lazaroid U-74389G with vitamin E-like properties effectively prevented the decrease in gamma-GT and GSH, so that direct inactivation of the membrane-bound gamma-GT by hyperoxia is the most likely mechanism. SN - 0190-2148 UR - https://www.unboundmedicine.com/medline/citation/9202959/Decrease_in_gamma_glutamyltransferase_activity_in_rat_type_II_cells_exposed_in_vitro_to_hyperoxia:_effects_of_the_21_aminosteroid_U_74389G_ L2 - http://www.tandfonline.com/doi/full/10.3109/01902149709039231 DB - PRIME DP - Unbound Medicine ER -