The research, which has implications for humans, marks the first time a link between a specific fetal lung protein and labor has been identified, said Dr. Carole Mendelson, professor of biochemistry and obstetrics and gynecology and senior author of the study. The paper appears in an upcoming issue of the Proceedings of the National Academy of Sciences and is currently available online.

The initiation of term labor is carefully timed to begin only after the embryo is sufficiently mature to survive outside the womb. Previous studies suggested that the signal for labor in humans may arise from the fetus, but the nature of the signal and actual mechanism was unclear, Dr. Mendelson said.

In their study, UT Southwestern researchers found evidence that a substance secreted by the lungs of a developing fetus contains the key signal that initiates labor. The substance, called surfactant, is essential for normal breathing outside the womb.

"We found that a protein within lung surfactant serves as a hormone of labor that signals to the mother's uterus when the fetal lungs are sufficiently mature to withstand the critical transition to air breathing," Dr. Mendelson said.

"No one really understands what causes normal or preterm labor. There may be several chemical pathways that lead to labor, but we think that this surfactant protein, which is also produced by the fetal lung in humans, may be the first hormonal signal for labor," said Dr. Mendelson, who is co-director of the North Texas March of Dimes Birth Defects Center at UT Southwestern.

In humans the signaling protein, called surfactant protein A, or SP-A, also helps immune cells, called macrophages, fight off infections in the lungs of chil
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Contact: Amanda Siegfried
Amanda.siegfried@utsouthwestern.edu
214-648-3404
UT Southwestern Medical Center
22-Mar-2004