Plasma immunoreactive endothelin-1 concentration in cord blood of normal term neonates.

Plasma immunoreactive endothelin-1 (ir-ET-1) concentrations in cord blood of 20 term infants were measured by radioimmunoassay. The mean (+/- SEM) ir-ET-1 concentration was 1.04 +/- 0.29 pg/mL. There was no relationship between ir-ET-1 concentrations and race, sex, mode of delivery, and prenatal characteristics, such as cocaine exposure. The current methodologies were reviewed in an effort to explain the differences in ET-1 concentrations reported in various studies.