Localization of insulin-like growth factor (IGF-I) and IGF-I receptor expression in human corpora lutea: Role on estradiol secretion

Objective: To determine whether insulin-like growth factor (IGF-I) and its receptors are expressed by human corpus luteum (CL) and to establish the effect of IGF-I on E(2) biosynthesis in human luteal cell cultures. Design: Middle corpora lutea were obtained from women undergoing surgical sterilization. The tissue was frozen for binding and in situ studies or dispersed for cell cultures. Setting: Procedures were performed at the San Borja-Arriaran Hospital, National Health Service, and Institute of Maternal and Child Research, Faculty of Medicine, University of Chile. Patients: Twelve patients aged 30 to 40 years requesting surgical sterilization in our institution. The laparotomy was scheduled 6 to 8 days after ovulation. Main Outcome Measures: Expression of IGF-I and IGF-I receptor messenger RNAs (mRNAs) by in situ hybridization. Concentration of IGF-I receptor and binding characteristics. Production of E(2) by luteal cells. Results: The binding of IGF-I was detected in middle human CL membranes. In addition, this tissue expressed the mRNAs of IGF-I and its receptor. In culture, IGF-I caused a progressive increase on E(2) production. Conclusion: These data suggest that the IGF-I system is present in middle human CL. The topographic distribution of IGF-I and its receptors and the ability of IGF-I to stimulate E(2) secretion strongly suggest that IGF-I has a role as a paracrine or autocrine regulator of the human luteal function.