Changes in Proliferative Response and Sensitivity of Placental Cells to Epidermal Growth Factor during Pregnancy in the Rabbit

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The regulatory role of epidermal growth factor (EGF) in the rabbit placental growth has been elucidated by investigating the proliferative response and sensitivity of placental cells to EGF during pregnancy. Trophoblastic cells were isolated from rabbit placental tissues from days 11, 17, 23 and 29 of pregnancy. The cells were incubated with a varying concentration of EGF and exposed to 100μM bromodeoxyuridine (BrdU). The BrdU incorporation, evaluated by an enzyme-linked immunosorbent assay (ELISA), was significantly stimulated by EGF on days 11 and 17 when more than 2.5 and 5.0 nM was added, respectively, but not on days 23 and 29 up to 160 nM. Scatchard analysis of the specific 125I-labelled EGF binding to the cells revealed two classes of binding sites. Their dissociation constants (Kd) in both high-and low-affinity binding sites were not significantly different among days of pregnancy. However, the number of binding sites per cell (Bmax) significantly decreased with progress of pregnancy: 4, 154 ± 1, 255 sites/cell (mean ± SEM) to 834 ± 79 in the high-affinity site and 13, 064 ± 5, 983 to 2, 924 ± 785 in the low-affinity site from day 11 to 29. These results suggest that the signal mediated by EGF receptor is a regulatory factor for the rabbit placental growth and that EGF may be involved in the regulation.
日本繁殖生物学会の論文