Exogenous action of 5-lipoxygenase by its metabolites on luteinizing hormone release in rat pituitary cells

Abstract

The stimulatory effect of exogenously administered potato 5-lipoxygenase (0.1–0.3 U/2 ml) on luteinizing hormone (LH) release was demonstrated in rat anterior pituitary cells in a superfusion system. Nordihydroguaiaretic acid (NDGA), an inhibitor of 5-lipoxygenase, abolished the effect of the enzyme on LH secretion. The secretory effect on LH after 5-lipoxygenase administration was biphasic and dependent on Ca 2+ indicating that 5-lipoxygenase affects LH release through its oxygenation reaction. Another series of experiments demonstrated that activation of 5-lipoxygenase, expressed as production of leukotriene (LT) B 4 and C 4 (728 ± 127 pg/10 6 cells and 178 ± 23 pg/10 6 cells, respectively) occurs in rat pituitary cells after addition of Ca 2+ ionophore A23187. However, LTB 4 and LTC 4 were not formed by pituitary cells that had previously been desensitized by gonadotropin-releasing hormone (GnRH), the physiological ligand of LH release. These results are consistent with a role of 5-lipoxygenase metabolites in the mechanism of GnRH-induced LH secretion.