TRANSFORMING GROWTH FACTOR-ALPHA AND EPIDERMAL GROWTH-FACTOR MESSENGER-RIBONUCLEIC-ACID AND PROTEIN-LEVELS IN HUMAN PLACENTAS FROM EARLY, MID, AND LATE GESTATION

OBJECTIVE: Human placenta expresses receptors for transforming growth factor-alpha and epidermal growth factor throughout pregnancy. Experiments were performed to determine whether epidermal growth factor or transforming growth factor-alpha might be synthesized by placental cells and act through an autocrine mechanism to influence functioning of placental cells in vivo. STUDY DESIGN: Human placentas from early, mid, and late gestations were analyzed for transforming growth factor-alpha and epidermal growth factor messenger ribonucleic acid and proteins. Polyadenylic acid-positive ribonucleic acid was isolated from placentas from 10, 11, 13, 21, 32, 38, 39, and 40 weeks of gestation and analyzed by Northern analysis for hybridization with complementary deoxyribonucleic acid probes specific for epidermal growth factor or transforming growth factor-alpha. Levels of immunoreactive epidermal growth factor and transforming growth factor-alpha were measured by specific radioimmunoassays in pools of placentas from early, mid, and late gestations, and levels of epidermal growth factor and transforming growth factor-alpha receptor-active protein were measured by radioreceptor assay. RESULTS: All placentas had a strong transforming growth factor-alpha hybridization band at 4.5 kb and a weak epidermal growth factor hybridization band at 5.2 kb. High levels of transforming growth factor-alpha immunoreactive protein (90 to 180 ng/mg protein) and low levels of immunoreactive epidermal growth factor (3 to 9 pg/mg protein) were detected in pools of placentas from early, mid, and late gestations. High levels of epidermal growth factor and transforming growth factor-alpha receptor-active protein (250 ng/mg protein) were also detected. CONCLUSION: Human placentas contain relatively high levels of immunoreactive and receptor-active transforming growth factor-alpha, as well as transforming growth factor-alpha messenger ribonucleic acid, throughout gestation. This finding suggests that transforming growth factor-alpha may act by an autocrine system to influence human placental cell function in vivo.