EFFECT OF GLUTATHIONE ON ENDOTHELIAL PROSTACYCLIN SYNTHESIS AFTER ANOXIA

We previously observed decreased prostacyclin (PGI2) formation after r eoxygenation of anoxic endothelium. In the present study, the effects of glutathione on endothelial prostaglandin (PG) H synthase activity a fter reoxygenation were explored. Intracellular glutathione content de creased 70% after 24 h of anoxia; reoxygenation did not produce any ad ditional decrease in glutathione content. Intracellular glutathione wa s maintained in the reduced state by the endothelium even during the o xidant stress caused by reoxygenation or the addition of peroxide. Glu tathione depletion produced by DL-buthionine-(S,R)-sulfoximine (BSO), 1,3-bis(chloroethyl)1-nitrosourea (BCNU), or incubation in a sulfhydry l-free medium resulted in increased sensitivity of PGH synthase to the effects of added H2O2. However, glutathione depletion resulting from BSO or culture in sulfhydryl-free medium during anoxia did not increas e the sensitivity of PGH synthase to reoxygenation. In addition, anoxi a did not make the endothelium more sensitive to H2O2. Glutathione per oxidase and glutathione reductase activities were preserved after anox ia-reoxygenation. When glutathione reductase was inhibited with BCNU d uring reoxygenation, PGI2 release was decreased further. These finding s demonstrate that, although anoxia decreases endothelial glutathione content, the endothelium is able to utilize its remaining glutathione to protect against additional oxidant stress because glutathione perox idase and glutathione reductase retain their activity.