Role of apical and basolateral secretion in turnover of glutathione in LLC-PK1 cells

Publisher Website
Google Scholar
Abstract
Previous clearance measurements have established that the rapid turnover of renal proximal tubular glutathione is in part due to apical secretion and degradation by gamma-glutamyltranspeptidase, an ectoenzyme that is primarily associated with the brush-border membrane. The relationship between glutathione turnover and secretion was further characterized using confluent cultures of LLC-PK1 cells grown on nitrocellulose supports. The resulting cell layer was impermeable to [3H]inulin and exhibited a polarized expression of gamma-glutamyltranspeptidase. Incubating cells with 5 mM buthionine sulfoximine, an inhibitor of glutathione synthesis, produced an 86% inhibition of [35S]cystine incorporation into intracellular glutathione. Under these conditions, the prominent intracellular pool of glutathione turns over with an apparent half-life of 4 h and a first-order rate constant of 0.17 h-1. This turnover is unaffected by pretreatment with AT-125, an inhibitor of gamma-glutamyltranspeptidase. The rate of accumulation of glutathione in the apical and basolateral medium of cells pretreated with AT-125 was 22 and 34 nmol.mg protein-1.h-1, respectively. The combined secretion was equivalent to the calculated turnover rate of intracellular glutathione (57 nmol.mg protein-1.h-1). Therefore, the combined processes of apical and basolateral secretion can account for the turnover of intracellular glutathione in LLC-PK1 cells.

This publication has 0 references indexed in Scilit: