THE EFFECTS OF ATRIAL-NATRIURETIC-FACTOR AND ANGIOTENSIN-II ON FETAL-PLACENTAL PERFUSION-PRESSURE IN THE EX-VIVO COTYLEDON MODEL

OBJECTIVE: Our purpose was to investigate pressure changes induced by angiotensin II on placental vasculature pretreated with atrial natriuretic factor. STUDY DESIGN: A dual-perfused cotyledon model was used. Two cotyledons from each placenta were perfused. One cotyledon was infused with atrial natriuretic factor for 30 minutes while the other received an equal volume of saline solution. Three atrial natriuretic factor concentrations were studied: 50 pg/ml, 150 pg/ml, and 15 ng/ml. Both cotyledons received injections of angiotensin II, at the following doses: 1 x 10(-11.5), 1 x 10(-11), 1 x 10(-10.5), and 1 x 10(-10) mol. RESULTS: Cotyledons subjected to 50 pg/ml and 150 pg/ml concentrations of atrial natriuretic factor did not differ in pressure responses to angiotensin II, compared with the saline-infused cotyledons (p > 0.05). The 15 ng/ml concentration of atrial natriuretic factor, however, decreased the presser response of angiotensin II (p < 0.034). CONCLUSIONS: Atrial natriuretic factor decreases vasoconstriction caused by angiotensin II. However, this was seen only at a supraphysiologic concentration. No effect was noted at normal fetal concentrations of atrial natriuretic factor.