PUTRESCINE UPTAKE IN RAT TYPE-II PNEUMOCYTES CORRELATES WITH GAMMA-GLUTAMYL-TRANSFERASE ACTIVITY

gamma-Glutamyltransferase (gamma GT) is a key enzyme in glutathione me tabolism and it is thought also to play a role in the uptake of polyam ines such as putrescine. The aim of our study was to investigate if ch anges in gamma GT activity would alter total putrescine uptake [P-up(t ot)], as well as more specific uptake via the gamma GT pathway [P-up(g amma GT)]. Forty-eight hours after their isolation, rat type II cells were exposed to 30, 60 or 125 mu M L-buthionine-[SR]-sulfoximine (BSO) for 3 hr; 200 or 800 mu M tertiary-butylhydroperoxide (t-BOOH) for 40 min; 10, 100 or 1000 mu M paraquat (PQ) for 1 hr; and 60 or 85% O-2 f or 48 hr. The gamma GT activity, P-up(tot) and P-up(gamma GT), (assess ed by inhibiting (GT) were measured immediately after the exposure to hyperoxia, or 24 hr after treatment with BSO, t-BOOH or PQ. From previ ous studies, it is known that these experimental conditions increased (BSO, 200 mu M t-BOOH) or decreased (800 mu M t-BOOH, PQ, hyperoxia) g amma GT activity. There was a strong correlation between the changes i n gamma GT activity and the changes in P-up(gamma GT) (r = 0.81, p < 0 .001). These findings support the hypothesis that gamma GT partly regu lates the uptake of putrescine, one of the polyamines required for cel l growth and differentiation. (C) 1997 Elsevier Science Ltd.