Epidermal growth factor receptors on isolated human placental syncytiotrophoblast plasma membrane

Receptor sites for mEGF that are specific, saturable and reversible have been demonstrated on isolated syncytiotrophoblast microvillous plasma membrane from term human placentae. Analysis of the binding data indicated the presence of two receptor populations. The high affinity population had 1.7 X 10(13) sites per mg membrane protein with an affinity constant (Ka) of 5.4 X 10(9)/M. The receptors of lower affinity had a Ka of 4.1 X 10(8)/M and 3.1 X 10(13) sites per mg membrane protein.