PERINATAL EXPRESSION OF IGFBPS IN RAT LUNG AND ITS HORMONAL-REGULATION IN FETAL LUNG EXPLANTS

To gain more insight into the regulation of the expression of insulin- like growth factor (IGF) binding proteins (IGFBPs) in the lung, the de velopmental patterns of the abundance of the mRNAs encoding IGFBPs wer e measured in the perinatal rat lung and in explant cultures of fetal rat lung. In hormone-free explant cultures, the levels of the mRNAs en coding IGFBP-2 through -5 changed with a pattern similar to that occur ring in vivo (although in the case of IGFBP-3 to -5 at a faster rate), indicating that the developmental regulation of the expression of the se IGFBPs in perinatal lung is mimicked in the explants. For the IGFBP -6 mRNA level, the pattern in vitro differed from that in vivo. In the explant cultures, dexamethasone decreased the production of IGFBP-3 a nd -4 and decreased the abundance of the mRNAs encoding IGFBP-2 to -5 but increased the abundance of IGFBP-6 mRNA. These observations indica te that glucocorticoids may be involved in the developmental regulatio n of the expression of these components of the IGF system and that the IGF system may be involved in the physiological effects of glucocorti coids on lung development. No appreciable effects of 3,3',5-triiodothy ronine on the expression of the IGFBPs were observed.