Putrescine uptake in rat type II pneumocytes correlates with γ-glutamyltransferase activity

Abstract

γ-Glutamyltransferase (γGT) is a key enzyme in glutathione metabolism and it is thought also to play a role in the uptake of polyamines such as putrescine. The aim of our study was to investigate if changes in γGT activity would alter total putrescine uptake [P up(tot)], as well as more specific uptake via the γGT pathway [P up(γGT)]. Forty-eight hours after their isolation, rat type II cells were exposed to 30, 60 or 125 μM l-buthionine-[SR]-sulfoximine (BSO) for 3 hr; 200 or 800 μM tertiary-butylhydroperoxide (t-BOOH) for 40 min; 10, 100 or 1000 μM paraquat (PQ) for 1 hr; and 60 or 85% O 2 for 48 hr. The γGT activity, P up(tot) and P up(γGT) (assessed by inhibiting γGT) were measured immediately after the exposure to hyperoxia, or 24 hr after treatment with BSO, t-BOOH or PQ. From previous studies, it is known that these experimental conditions increased (BSO, 200 μt-BOOH) or decreased (800 μM t-BOOH, PQ, hyperoxia) γGT activity. There was a strong correlation between the changes in γGT activity and the changes in P up(γGT) (r = 0.81, p < 0.001). These findings support the hypothesis that γGT partly regulates the uptake of putrescine, one of the polyamines required for cell growth and differentiation.