The insulin-like growth factor-II/mannose-6-phosphate receptor is present in fetal bovine tissues throughout gestation

The insulin-like growth factor-II (IGF-II) and the IGF-II/mannose-6-phosphate (M6P) receptor are thought to play an important role in fetal growth and development. We have studied the expression of the IGF-II/M6P receptor in fetal bovine tissues from 5 through 36 weeks' gestation. Tissues from bovine fetuses were extracted in buffer containing 2% Triton-X-100 and 2% sodium dodecyl sulfate (SDS). Aliquots of the protein extracts were analyzed by SDS polyacrylamide gel electrophoresis and the protein bands were transferred onto nitrocellulose. Immunoblotting was performed with anti-bovine IGF-II/M6P receptor antiserum. In a subset of experiments, ligand blotting was carried out with radiolabeled IGF-II and subsequent autoradiography. IGF-II/M6P receptors were expressed in all tissues examined, with the highest amount of receptor being present in fetal lung and liver. Low amounts of receptors were measured in fetal brain. The amount of receptor was developmentally regulated throughout fetal life. The developmental regulation of receptor expression varied among the different tissues. In conclusion, the IGF-II/M6P receptor is present in all fetal bovine tissues examined. The presence of the IGF-II/M6P receptor seems to be developmentally regulated during bovine fetal life. We hypothesize that this receptor exerts important biologic effects during fetal growth and tissue and organ development.