ONTOGENY OF INSULIN-LIKE GROWTH-FACTOR-I AND GROWTH-FACTOR-II GENE-EXPRESSION IN OVINE FETAL HEART

OBJECTIVE: Insulin-like growth factors (IGF)-I and -II have been impli cated in growth and differentiation during embryonic and fetal develop ment. To examine the role of the IGFs in growth of the fetal heart, we determined the gene expression of IGF-I and IGF-II in the four cardia c chambers of the ovine fetus from 58 to 146 days' gestation (term = 1 47 days). METHODS: Total RNA was obtained from the cardiac chambers, a nalyzed by Northern blot, and hybridized to ovine specific cDNA probed for IGF-I and IGF-II. The resulting autoradiograms were subjected to light densitometry, and the intensity of the IGF signals was normalize d to the respective 28S ribosomal RNA signals. RESULTS: In the atria a nd ventricles, IGF-I mRNA abundance was very low throughout the gestat ional period studied, whereas IGF-II mRNA levels were higher and readi ly detectable. In the atria, IGF-I mRNA was very low at 60 days' gesta tion and appeared to increase gradually toward term. Abundance of IGF- II mRNA was high at 60 days, increased further until 120 days, and dec reased slightly toward term. In contrast, in the ventricles, IGF-I mRN A increased from 60 to 100 days and then declined moderately at term. Levels of IGF-II mRNA in the ventricles were high at 60 days and decre ased progressively to low levels at term. No difference in IGF-I or IG F-II mRNA levels was noted between the right and left atria or right a nd left ventricles. CONCLUSIONS: These results suggest that developmen tal patterns for IGF-I and IGF-II gene expression exist in the ovine f etal heart, and the patterns differ between the atria and ventricles. Further, these gestational trends differ from those for atrial natriur etic factor (ANF) found in our precious studies, indicating that expre ssion of the ANF gene in the fetal heart may not be associated with ca rdiac growth and differentiation. Copyright (C) 1996 by the Society fo r Gynecologic Investigation.