Possible Involvement of Lipoxygenase Products in Human Corpora lutea

Abstract

The present study was undertaken to determine the ability of cultured luteal cells from human corpora lutea to secrete progesterone (P₄) and prostaglandins (PGs), and to assess the effects of the products of the lipoxygenase pathway on luteal P₄ production. Luteal cells responded to human chorionic gonadotropin (hCG) with a significant increase (2- to 7-fold) in P₄ production. Arachidonic acid significantly stimulated PGE₂ synthesis by luteal cells in a dose-dependent manner. Both basal PGE₂ production and the responsiveness to arachidonic acid were maintained for 8 days. In contrast, both PGF_2α and 6-keto-PGF_1α production abruptly declined as the culture proceeded. However, the addition of hCG did not further stimulate the accumulation of the 3 PGs assayed. In the subsequent experiment, 5-hydroxyeicosatetraenoic acid (5-HETE) and the reaction products of soybean lipoxidase of arachidonic acid (AA-LIP) were utilized for evaluating the involvement of the lipoxygenase pathway in luteolysis. The addition of 5-HETE dose-dependently inhibited P₄ production by the cultured luteal cells. Although treatment with either arachidonic acid or lipoxidase alone had no effect on P₄ production, AA-LIP significantly reduced P₄ production in the presence or absence of hCG. These results suggest that the products of the lipoxygenase as well as of the cyclo-oxygenase pathway may be important in regulating the life span and function of human corpora lutea.