Placental IGF-I in Severe Intrauterine Growth Retardation

IGF-I, which is produced by intrauterine tissues including the placenta, has been implicated as a possible factor in intrauterine growth retardation (IUGR). We hypothesized that placental IGF-I production may be aberrant in pregnancies affected by IUGR. A placental perifusion system was utilized to study the release of IGF-I in placentas from normotensive severe IUGR (birthweight < 5%, (n = 9)) and normal control pregnancies (n = 5). For each placenta, tissues were perifused and samples were collected from hour 5 to hour 10. IGF-I was measured by radioimmunoassay after acid extraction. The cumulative release of total IGF-I from the control placentas from hour 5 to hour 10 of perifusion was 15,417 ± 1,337 pg/g (mean ± SEM), and decreased ∼45% from hour 5 through hour 10 of perifusion. The pattern of IGF-I release, as well as the absolute mass of IGF-I, from six of the nine IUGR placentas was similar to the controls. However, three of the nine IUGR placentas demonstrated a significantly different IGF-I release pattern, i.e., IGF-I release did not decrease throughout the perifusion period. These three placentas also had abnormal absolute production rates of IGF-I, i.e., significantly elevated in one and significantly decreased in two. IGF-I production and release were normal in some IUGR placentas, although in certain cases of IUGR, the placental production and release pattern were aberrant. We conclude that abnormal regulation and production of IGF-I by the placenta may be a factor affecting certain pregnancies complicated by IUGR.