ldentification of the main IGF binding proteins (IGFBPs) in normal rat tissues

Abstract

We investigated the presence of the main IGF-I binding proteins in rat tissues and the size of the complexes formed in each case. WLB and gel filtration chromatography were used to separate and identify four binding proteins: IGFBP-1 to IGFBP-4. In al1 the tissues studied, the presence of IGFBP-3 was detected, although its concentration seemed to change in each case, being most abundant in liver, kidney and heart, and less in lymphoid organs (spleen and thymus). IGFBP-1 and IGFBP-2 were found in liver and lung and also in heart and skeletal muscle, where their messenger RNAs, had not been previously reported, as is the case of the presence of IGFBP-4, identified in lung in the present study. In conclusion, our results show a typical profile for the IGFBPs, depending on the tissue, although it is not clear yet if they are the result of in situ synthesis or transcapillary transport. A better knowledge of their expression will give insight into their regulatory role on the IGF-I bioavailability in the different tissues.