The presence of platelet-activating factor binding sites in human myometrium and their role in uterine contraction

It has recently been suggested that platelet-activating factor is involved in a number of processes associated with reproductive biology. We have demonstrated a critical role for this autacoid in the initiation and maintenance of parturition both in animals and man. In the present investigation, it has been demonstrated that platelet-activating factor affects contraction in strips of human myometrium at concentrations as low as 10⁻¹⁰ mol/L. A platelet-activating factor receptor has been identified and characterized in human myometrium. Platelet-activating factor acts to cause an increase in intracellular Ca²⁺ concentration of isolated myometrial smooth muscle cells in culture and an increase in the phosphorylation of the 20 kd light chain of myosin in a concentration-dependent fashion. The presence of platelet-activating factor receptors in human myometrium, the observed increase in Ca⁺² concentration and phosphorylation of myosin light chain in the presence of platelet-activating factor provide further support for the importance of this autacoid in the initation of parturition.