mRNA of insulin-like growth factor (IGF) quantification and presence of IGF binding proteins, and receptors for growth hormone, IGF-I and insulin, determined by reverse transcribed polymerase chain reaction, in the liver of growing and mature male cattle
P. Cordano et al., mRNA of insulin-like growth factor (IGF) quantification and presence of IGF binding proteins, and receptors for growth hormone, IGF-I and insulin, determined by reverse transcribed polymerase chain reaction, in the liver of growing and mature male cattle, DOM ANIM EN, 19(3), 2000, pp. 191-208
Plasma insulin-like growth factor-I (IGF-I) concentrations were related to
hepatic levels of IGF-I mRNA measured by competitive reverse transcription
polymerase chain reaction (PCR) (RT-PCR) in neonatal (8 d old) calves, veal
calves, fattened castrated bulls and mature intact bulls. Furthermore, the
presence of mRNAs of IGF-II and of receptors for IGF-I (ICF-IR), growth ho
rmone (GHR) and insulin (IR), as well as mRNAs of IGF binding proteins (IGF
BP-1, -2 and -3) were assessed by RT-PCR. Hepatic ICF-I mRNA levels and pla
sma IGF-I concentrations in veal calves, fattened castrated bulls and in in
tact bulls were 4 to 8 times higher than in 8-d old calves and were 2 to 3
times higher in calves fed colostrum than in calves fed only milk replacer.
Hepatic IGF-I mRNA concentrations were closely correlated (r = 0.92) with
plasma IGF-I concentrations, suggesting that hepatic IGF-I production large
ly determines plasma IGF-I levels. The presence of ICF II, IGF-IR, GHR, IR
and IGFBP-1, -2 and -3 mRNA was confirmed in the liver of 8-d old calves an
d older cattle as well, and among newborn calves their presence was indepen
dent of differences in nutrition. In conclusion, the major hepatic componen
ts of the GH-IGF axis were present in neonatal calves, but the IGF-I expres
sion and therefore also plasma IGF-I levels were relatively low. (C) 2000 E
lsevier Science Inc. All rights reserved.