Effects of a long-acting analogue of LH releasing hormone on human and rat corpora lutea

Abstract

Dispersed luteal cells were prepared both from samples of human corpora lutea obtained during normal menstrual cycles and from luteinized rat ovaries of animals pretreated with pregnant mare's serum gonadotrophin and human chorionic gonadotrophin (hCG). Addition of the long-acting analogue, D-Ala6-des-Gly10-LH releasing hormone ethylamide (D-Ala6-LHRH), to rat luteal cells caused a small but significant increase in progesterone production. An inhibitory action of the analogue on hCG-stimulated steroidogenesis by rat luteal cells was confirmed. Addition of D-Ala6-LHRH to suspensions of human luteal cells had no effect on either basal or hCG-stimulated progesterone production. Studies on the interaction of 125I-labelled D-Ala6-LHRH with the dispersed cell preparations, while confirming the presence of displaceable binding to rat luteal cells, failed to detect any equivalent binding to human luteal cells. Low levels of displaceable binding observed using homogenates of human corpora lutea are interpreted as being of doubtful physiological significance in view of the negative findings obtained with the intact cell system.