| 1 Studies on Growth and Developmental Changes of Serum Level of Some Hormones and Expression of Target Genes for Growth Hormone Action in Erhualian pigs and Large White pigsIn order to research the neuroendocrinological and molecular biology mechanism of animal growth and development, purebred male Large White (LW), male and female Erhualian (EHL) pigs with significant differences in growth rate were employed in present study to investigate the developmental changes of serum levels of some hormones and expression of target gene for growth hormone action in the liver and skeletal muscle. The animals were fed according to the breeding standards of USA NRC and Chinese Local Pigs respectively. Four piglets of each breeds or sexes (EHL) were slaughtered at 0, 3, 20, 30, 45, 90, 120 and 180 day respectively for liver, longissimus dorsi (LD) muscle and blood sampling. Serum levels of leptin, insulin, glucagon, T3 and T4 were determined by RIA. The total RNA of liver and LD muscle was extracted and the abundance of liver growth hormone receptor (GHR), insulin-like growth factor 1(IGF-I) and IGF-IR messenger ribonucleic acid (mRNA) was determined by relative quantitative reverse transcription polymerase chain reaction (RT-PCR) with 18S rRNA as internal standard. Results showed as follows:1.1 Developmental changes of body, liver and LD weight gain in EHL and LW pigs. From day 0 to day 180, the body weight (BW), average daily body weight gain (ABWG), liver weight, average daily liver weight gain (DLWG), LD muscle weight, average daily LD weight gain (DLDWG) and rate of LD weight to body weight of male LW at each age were higher than those of male EHL. However, no significant differences of relative liver weight to body weight between male EHL and LW pigs, BW, ABWG, liver weight, LD weight, rate of liver and LD weight to BW, DLWG and DLDWG between male and female EHL pigs were found.1.2 Developmental changes of serum levels of some hormones in EHL and LW pigs. (1) The pattern of developmental changes of serum level of leptin in EHL and LW pigs were similar, which being low before day 30 and high from day 90 to day 180 in both breeds. The serum leptin concentration was higher in male EHL pigs than in male LW pigs (P<0.01), and in female than in male EHL (P<0.01). (2) Similar developmental changes of serum level of T3 or T4 in EHL and LW pigs were also observed. There was higher serum level of T4 (P<0.05) but T3 (P>0.05) in male EHL pigs than in male LW pigs, while both T3 (P>0.05) and T4 (P>0.05) were not markedly different between male and female EHL pigs. (3) The serum insulin concentration in male EHL pigs had a potential increase from day 0 to day120 and then potential decrease, while in male LW it had a potential increase from birth to day 20 and no significant changes thereafter. The serum level of insulin in male LW was lower than that in EHL (P<0.01), while there was no detectable difference of serum glucogan level between breeds (P>0.05)1.3 Developmental changes of hepatic GHR, IGF-I and IGF-IR mRNA abundance in EHL and LW pigs. (1) The pattern of developmental changes of relative abundance of hepatic GHR mRNA in EHL and LW pigs were similar, which increased with age before day 120 and kept high level thereafter. The relative abundance of hepatic GHR mRNA was lower in male EHL than in male LW (P<0.01), but not than in female EHL pigs (P>0.05). (2) The changes of hepatic IGF-I mRNA abundance and the protein level of IGF-I in liver tissue with ages were consistent with that of hepatic GHR mRNA abundance. There was a strong correlation between GHR and IGF-I mRNA level (R=0.70, P<0.01, R=0.58 in LW, P<0.01; R=0.75 in EHL, PO.01), GHR mRNA and IGF-I protein level (R=0.67, P<0.01), IGF-I mRNA and protein level (R=0.78, P<0.01). The ABWG also correlated strongly with hepatic GHR mRNA (R=0.95, PO.01), IGF-I mRNA (R=0.91, PO.01) and IGF-I protein level (R=0.97, PO.01). The IGF-I mRNA (PO.01) and protein level (PO.05) were lower in male EHL pigs than male LW pigs, but not than in female EHL pigs (P>0.
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