Ontogeny of IGFs and IGFBPs mRNA levels and tissue concentrations in liver, kidney and skeletal muscle of pig.

As far as we know, there is no available information about ontogenic changes of tissue concentrations of IGF-I and II and IGFBPs in large mammals. Serum, liver and kidney levels of IGFs and IGFBPs were examined in fetuses at 90 and 110 days of gestation and in pigs at 1d, 3 wk, 3 mo and 6 mo of age. Ontogeny of mRNA levels of IGFs, IGF type I and type II receptors (IGFI-R and IGFII-R), IGFBP-1 and -3 (IGFBPs) and growth hormone receptor (GHR) were also examined by Northern blot analysis in liver, kidney and skeletal muscle of pig. Serum IGF-I, IGF-II and IGFBP-3 concentrations were low during the fetal life and increased after birth. The highest level of IGF-II mRNA was found in fetuses for all studied tissues. In the liver, IGF-I mRNA level and its protein content peaked at 3 wk of age. The highest IGF-II concentration was found at 1d and 3 wk of age. The IGFII-R mRNA remained at a constant level during the whole development period. The most abundant IGFBP-1 mRNA and its protein content were found at birth. The level of IGFBP-2 was high during fetal and early postnatal life. The IGFBP-3 content was relatively low in fetuses and reached the highest level after 3 wk of age. In the kidney, IGFs, IGFBP-3, IGFI-R and IGFII-R as well as GHR mRNA levels were relatively high during the fetal and early postnatal life. The IGFs concentrations were the highest in newborns. In the skeletal muscle, IGFs, IGFBP-3 and IGFI-R mRNA levels decreased with advancing age. During the postnatal life, the high IGFs concentrations in the liver and the kidney correspond to fast growth periods of these organs.