Inhibition of the A-23187-stimulated leukotriene and prostaglandin biosynthesis of rat basophil leukemia (RBL-1) cells by nonsteroidal anti-inflammatory drugs, antioxidants, and calcium channel blockers.

Rat basophil leukemia cells (RBL-1), when grown in monolayer, synthesize from endogenous substrates the prostaglandins (PG) E2, F2 alpha, and I2 (measured as 6-keto-PGF1 alpha) and 6-sulfidopeptide-containing leukotrienes (SRS), as well as materials that react serologically with anti-12-hydroxyeicosatetraenoic acid (HETE). The non-steroidal anti-inflammatory drugs indomethacin and aspirin inhibited PGE2 synthesis by RBL-1 cells, which had been stimulated with the calcium ionophore A-23187, in a dose-dependent manner with an IC50 of 0.7 and 7.8 microM respectively. Indomethacin, when used at higher concentrations, also inhibited iSRS synthesis with an IC50 of 230 microM. Benoxaprofen, also a non-steroidal anti-inflammatory drug, inhibited both PGE2 and iSRS production in a dose-dependent manner, but inhibition of the iSRS biosynthesis was three times more effective than inhibition of PGE2 production. The anti-oxidants gossypol, butylated hydroxyanisole (BHA), nordihydroguariatic acid (NDGA), and 3-amino-1-[m-(trifluoromethyl)phenyl]-2-pyrazoline (BW755c) also inhibited iSRS synthesis more effectively than PGE2 biosynthesis. The IC50 values for inhibition of iSRS production were 0.2 microM (gossypol), 0.5 microM (BW755c), 0.6 microM (BHA), and 0.6 microM (NDGA) compared to 2.8 microM (gossypol), 2.0 microM (BW755c), 4.8 microM (BHA) and 2.6 microM (NDGA) for inhibition of PGE2 synthesis. Gossypol, BW755C, BHA, and NDGA, as well as benoxaprofen, inhibited i12-HETE-biosynthesis (IC50 for gossypol, 0.32 microM; and for benoxaprofen, 0.5 microM). Two calcium channel blockers, verapamil and nifedipine, inhibited PGE2, iSRS and i12-HETE synthesis in a dose-dependent manner. The calcium channel blockers inhibited iSRS synthesis ten times more effectively than PGE2 production.