ALTERATION IN IGF-I MESSENGER-RNA CONTENT OF FETAL SWINE TISSUES IN RESPONSE TO MATERNAL DIABETES

Diabetes alters the level of insulin-like growth factor I (IGF-I) mRNA in tissues of postnatal animals, but the impact of maternal diabetes or gestational diabetes on IGF-I mRNA abundance in fetal tissues has n ot been examined; Pregnant pigs were injected with either buffer or al loxan (50 mg/kg) at day 75 of gestation to induce diabetes. Fetal tiss ue samples were collected at clay 105 of gestation, and IGF-I mRNA abu ndance (densitometric units/10 mu g total RNA) were estimated by speci fic ribonuclease protection assay. Fetal glucose and IGF-I concentrati ons were increased 166 and 34%, respectively, by maternal diabetes. Ma ternal diabetes induced an increase in abundance of IGF-I mRNA in feta l skeletal muscle, liver, heart, kidney, and placenta. IGF-I mRNA leve ls were depressed by maternal diabetes in fetal adipose tissue and bra in compared with the respective tissues from fetuses of control pigs. These data indicate that circulating levels of IGF-I and the steady-st ate levels of IGF-I mRNA in fetal tissues can respond to the metabolic and endocrine alterations occurring during maternal diabetes. The lar ge variation in expression and degree of response among fetal tissues indicates that the fetus experiences tissue-specific regulation of IGF -I expression during development.