• Asian-Australasian Journal of Animal Sciences
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• 제27권1호
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• pp.147-154
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• 2014

This review focuses on modulation of growth hormone (GH) and its downstream actions on periparturient dairy cows undergoing physiological and metabolic adaptations. During the periparturient period, cows experience a negative energy balance implicating that the feed intake does not meet the total energy demand for the onset of lactation. To regulate this metabolic condition, key hormones of somatotropic axis such as GH, IGF-I and insulin must coordinate adaptations required for the preservation of metabolic homeostasis. The hepatic GHR1A transcript and GHR protein are reduced at parturition, but recovers on postpartum. However, plasma IGF-I concentration remains low even though hepatic abundance of the GHR and IGF-I mRNA return to pre-calving value. This might be caused by alternation in IGFBPs and ALS genes, which consequently affect the plasma IGF-I stability. Plasma insulin level declines in a parallel manner with the decrease in plasma IGF-I after parturition. Increased GH stimulates the lipolytic effects and hepatic glucose synthesis to meet the energy requirement for mammary lactose synthesis, suggesting that GH antagonizes insulin-dependent glucose uptake and attenuates insulin action to decrease gluconeogenesis.

• Asian-Australasian Journal of Animal Sciences
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• 제21권9호
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• pp.1244-1251
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• 2008

The aim of the present study was to delineate the expression and secretion of insulin-like growth factor (IGF) system components by pig liver cells. Hepatocytes were prepared from 3-wk-old weanling piglets following a two-step collagenase perfusion procedure, after which the cells were incubated for 24 or 48 h at a density of $2{\pm}10^5$ cells per 35-mm dish in 2-ml Williams' medium E. The cells were found to express the genes encoding IGF-I, IGF-binding proteins (IGFBPs)-2 and -3 and acid-labile subunit (ALS) by reverse transcription-polymerase chain reaction (RT-PCR) following the culture. However, IGF-I was localized to hepatocytes by immunohistochemical analysis, whereas IGFBP-3 was localized to endothelial cells, but not to hepatocytes. This indicated that the IGFBP-3 gene expression detected by RT-PCR was likely to have been contributed by unidentified non-parenchymal cells that had not been removed during the hepatocyte preparation. The conditioned culture medium (CCM) of the cells contained immunoreactive IGF-I and IGF-II, with the latter being seven-fold more abundant than the former. The CCM also contained 43-, 40-, 34-, 31-kDa doublet and 26-kDa IGFBPs as examined by Western ligand blotting. The 40-, 34- and 31-kDa doublet IGFBPs were approximately three-fold as abundant as the 43- and 26-kDa IGFBPs. Moreover, the 43- and 40-kDa doublet and the 34-kDa IGFBPs were immunoprecipitable with IGFBP-3 and IGFBP-2 antibodies, respectively. Overall, these results are similar to those known in the rat, which suggests that the IGF system components are likely to be expressed and secreted in pig liver in a manner similar to that in rat liver.