Effects of diethyl maleate (DEM), a glutathione depletor, on prostaglandin synthesis in the isolated perfused spleen of rabbits

Abstract

To investigate the role of glutathione (GSH) on prostaglandin (PG) synthesis, isolated rabbit spleens were perfused with Tyrode's solution with or without the addition of diethyl maleate (DEM) in concentrations up to 1 mM. In the absence of DEM, PG synthesis was stimulated by the Ca²⁺ ionophore A23187 (20 nmole) or arachidonate (0.4 μmole). Prostaglandin (PG) E₂ was a major product, accounting for 60–70% of the total cyclooxygenase products. Small amounts of PGF₂α, 6-keto-PGF₁α, PGD₂ and thromboxane (Tx) B₂ were also produced. When DEM was added to the perfusion medium, GSH content decreased dose-dependently with increasing DEM concentration. Lactate dehydrogenase activity was not detected in the venous effluent, indicating that DEM depleted intrasplenic GSH without causing any lysis of cellular membranes. A23187-induced production of PGs and of Tx was decreased with increasing concentrations of DEM up to 0.5 mM, whereas at 1.0 mM DEM, these products showed a tendency to increase as compared with levels at 0.5 mM DEM. However, this increase was only significant for TxB₂, which returned to levels obtained in the absence of DEM. DEM 1 mM did not cause cell lysis, but it appears to perturb the cell membrane to a degree similar to that which occurs with stimulation of phospholipase A₂. The small but significant increase of TxB₂ with 1.0 mM DEM could be a result of decreased PGE₂ isomerase activity. Perfusion with arachidonate gave virtually identical results: 1.0 mM DEM attenuated the production of all prostanoids except for TxB₂ as compared with untreated controls. These results suggest that GSH contributes to the regulation and/or maintenance of PGs synthesis.