OBJECTIVES:To assess the ligand binding characteristics of insulin and insulin-like growth factor I receptors in normal and preeclamptic placentas. DESIGN AND METHODS:This study was done cross sectionally in trophoblast membranes obtained from 10 normotensive and 9 preeclamptic pregnant women. The affinity and number of binding sites of insulin and insulin-like growth factor I receptors were assessed by binding assays and Scatchard plot analysis. RESULTS:Placental and newborn birth weights were significantly (P < 0.001) lower in the preeclamptic group. The K(d) values of placental insulin receptors (IR) were significantly higher in the preeclamptic group than in the normotensive group (1.08 +/- 0.24 x 10(-9) vs. 0.81 +/- 0.13 x 10(-9) M, P < 0.01), without differences in the number of receptors. In contrast, no differences were observed in the affinity and the number of insulin-like growth factor I receptors (IGF-1R) between groups. Placental weight was associated negatively with the K(d) values of IR (P < 0.05) and positively with the number of placental IGF-1R (P < 0.05); while newborn birth weight was associated positively with the number of IGF-1R (P < 0.05). In addition, both systolic and diastolic blood pressure correlated significantly with K(d) values of placental IR (P < 0.01). CONCLUSIONS:These data demonstrate that preeclampsia is associated with low placental IR affinity. In addition, this study suggests an association between the affinity of IR and number of IGF-1R with placental and/or fetal growth. Furthermore, high blood pressure may affect the affinity of placental IR, but not the affinity or number of placental IGF-1 receptors.