Placental insulin and insulin-like growth factor I receptors in normal and preeclamptic pregnancies

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 Kd values of placental insulin receptors (IR) were significantly higher in the preeclamptic group than in the normotensive group (1.08 ± 0.24 × 10−9 vs. 0.81 ± 0.13 × 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 Kd 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 Kd 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.