Secretion of prostanoids by platelets and monocytes in normal and hypertensive pregnancies

OBJECTIVES: Secretory products of immune cells may induce or potentiate coagulation disturbances and vasoconstriction, both central features of pregnancy-induced hypertension. Women with chronic essential hypertension are at high risk of superimposed pregnancy-induced hypertension. The aim of our study was to compare secretory rates of prostanoids (active in coagulation and vascular reactivity) by peripheral blood monocytes and platelets from nonpregnant controls and from women in the third trimester of pregnancy, normals and those with either pregnancy-induced hypertension or uncomplicated chronic essential hypertension.

STUDY DESIGN: From 100 ml blood, peripheral blood monocytes and platelets were isolated; their relative rates of in vitro production of prostacyclin, prostaglandin E2, and thromboxane were measured, and responses to stimulation by arachidonic acid or the calcium ionophore A23187 were compared among the four groups of subjects.

RESULTS: Basal peripheral blood monocyte secretory levels of prostanoids were low in all groups, with responses to both stimuli. Cells from women with chronic essential hypertension had a relatively exaggerated rise in thromboxane secretion (and to a lesser extent, prostacyclin) in response to the stimuli used, with a similar but less marked trend for those with pregnancy-induced hypertension. Platelets from women with chronic essential hypertension had particularly high basal secretory levels of thromboxane, with little further response to stimulation by arachidonic acid or A23187.

CONCLUSIONS: Our work demonstrates clearly for the first time that peripheral blood monocytes from pregnant women secrete low levels of vasoactive prostanoids and respond to the stimuli used in a manner similar to that of nonpregnant women, and that cells from pregnant women with hypertension have a tendency to increased reactivity that is most marked in those with chronic essential hypertension. Platelets from women with chronic essential hypertension secrete near-maximal amounts of thromboxane in the absence of exogenous stimuli, indicating a degree of prior activation.