PLATELET-ACTIVATING-FACTOR IN HUMAN ENDOMETRIUM

Platelet-activating factor (PAF) is a phospholipid actively produced b y human endometrium and deeply involved in the processes of ovoimplant ation and labor. We recently found that PAF represents a new autocrine growth factor for a human adenocarcinoma eel line, HEC-1A. Indeed, bi ologically active PAF is synthesized by HEC-1A cells, under progestero ne control. In HEC-1A cells, PAF regulates intracellular calcium conce ntration ([Ca2+]), DNA synthesis and expression of early oncogenes. Al l these effects are blocked by the receptor antagonist L659,989. Howev er, while nanomolar concentrations of PAF mobilize [Ca2+], only microm olar concentrations affect cell growth, suggesting heterogeneity of PA F receptors or signaling. Two distinct populations of PAF receptors ar e present in HEC-1A cells, which bind PAF in nanomolar and micromolar concentrations, respectively. Since HEC-1A cells are producing elevate d concentrations of PAF and micromolar concentrations of the PAF antag onist L659,989 inhibit cell proliferation, an autocrine role for PAF i s suggested in HEC-1A cells.