This study was conducted to investigate the effects of dietary restriction and realimentation on energy and nitrogen on liver weight, proliferation and expansion of liver cells and expression levels of growth hormone receptor (GHR), insulin-like growth factor Ⅰ (IGF-Ⅰ) and insulin-like growth factor Ⅱ (IGF-Ⅱ) genes in liver of Mongolian lambs. Eighty lambs with similar body weight were divided into 4 groups: control group, protein-restricted group (PR), energy-restricted group (ER), and protein and energy-restricted group (BR). Lambs in the 4 groups were fed the diets with following nutrient levels during 60 days of restriction period: crude protein (CP was 15.08%, 9.24%, 15.01% and 6.27%, respectively, and accordingly, metabolizable energy (ME) was 10.61, 10.49, 8.36 and 8.10 MJ/kg, respectively. Then, lambs in the 4 groups were fed the same diet (CP) was 12.48% ME was 9.77 MJ/kg) during 90 days of realimentation period. At the end of restriction and realimentation periods, lambs were slaughtered to collect liver tissue for the analysis of liver weight, liver DNA content, and DNA and protein concentrations in liver cells. RT-qPCR were used to detect the expression levels of GHR, IGF-Ⅰ and IGF-Ⅱ genes. The results showed as follows: after 60 days of restriction period, liver weight of lambs in ER (P<0.05) and BR groups (P<0.01) was significantly lower than that in control group; liver cell counts of lambs in PR, ER and BR groups were lower than those in control group, no obvious expansion was found; IGF-Ⅰ gene expression level in PR, ER and BR groups was significantly lower than that in control group (P<0.05). After 90 days of realimentation period, no significant differences were found in liver weight, liver cell counts, liver cell size and the expression levels of GHR, IGF-Ⅰ and IGF-Ⅱ genes among all groups (P>0.05). The results indicate that after adapting restriction on lambs at 3 months of age, the inhibition effects of energy restriction on liver growth are larger than those of protein restriction, and those of restriction on protein and energy are the largest; down-regulation on the expression levels GHR, IGF-Ⅰ and IGF-Ⅱ genes of protein or energy restriction adapted alone was much more than that of restriction both on protein and energy; after dietary realimentaion, the indices of restricted lambs can be restored to the same level as that of unrestricted lambs.
ZHANG Dongmei
,
HOU Xianzhi
,
YANG Jinli
,
GAO Aiwu
,
WANG Hairong
,
KAO Guilan
. Dietary Restriction and Realimentation on Energy and Nitrogen: Effects on Liver Weight, Proliferation and Expansion of Liver Cells and Expression Levels of GHR and IGFs Genes in Liver of Mongolian Lambs[J]. Chinese Journal of Animal Nutrition, 2013
, 25(7)
: 1632
-1640
.
DOI: 10.3969/j.issn.1006-267x.2013.07.030
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