Developmental Changes Of GH Gene Expression In ErHuaLian Pigs And In Comparison With Large White Pigs

Erhualian (EHL) and Large White (LW) pigs with significant difference in growth rate were employed in present study to investigate the developmental changes of GH gene expression in pituitary from birth till 180 day of age by Northern Blot hybridization and relative quantitative RT-PCR. In order to study the role of GH and IGF- 1 in pituitary, the developmental changes of GH receptor (GHR) mRNA and IGF- 1 receptor (IGF- 1 R) mRNA were analyzed by RT-PCR in both breeds, as well as both sexes in EHL pigs. In addition, the serum IGF- 1 levels were measured via RIA and the possible correlation of these parameters with the growth performances was discussed. 1. Establishing methods for mRNA quantification Relative RT-PCR using QuantumRNATM 185 internal Standards for the quantitation of pGH mR.NA was established in present study. Meanwhile Northern Blot was established to validate the veracity and reliability of RT-PCR. The result indicated that RT-PCR was much more sensitive for detecting lowly expressed mRNAs in small tissues and the results obtained from RT-PCR were in good accordance with that obtained from Northern hybridization, indicating high reliability in mRNA quantitation. 2. Developmental changes of pituitary GH mRNA in pigs The pattern of developmental changes of pituitary GH mRNA in EHL and LW male pigs were similar, the peak GH mRNA level was found at day 0. At day 3 the GH mRNA levels declined in both breeds especially in EHL that was -6 9- significant. In accordance with body weight and growth rate, the GH mRNA levels of LW pigs were higher (P<0.01) than that of EHL pigs. Pituitary GH mRNA levels were higher in EHL male pigs than females at day 0 (P<0.01), but lower at day 90 (P<0.05). 3. Developmental changes of pituitary GHR and IGF-1R mRNA in EHL and Large White pigs The expression of pituitary GHR mRNA in pigs was not significantly correlated with the breeds, age and sex, this indicates that the GH might act more at hypothalamus rather than pituitary to regulate its own gene expression and that the pituitary GHR may be more related to autocrine and/or paracrine function of GH. The IGF-1R mRNA peak levels were found at day 0 both in EHL and LW pigs. After birth it subsequently declined till day 20, then rose slowly reaching the second peak at day 90. The developmental patterns of IGF-1R mRNA levels in EHL and LW pigs were similar. The first zenith (day 0) of IGF- 1 R mRNA may be involved in the modulation of pituitary development and the second correlated with the highest growth rate. At day 0 and 180, the pituitary IGF- 1 R mRNA level were higher in male EHL pigs than that of male LW pigs, but the opposite was true at day 30 and 90. As compared with the female EHL pigs, the IGF-1R mRNA levels of EHL male pigs were significantly higher at day 0 and 180 but lower at day 90. 4. A comparative study on serum IGF-1 levels in male EHL and Large White pigs IGF- 1 levels increased progressively from day 0 to day 90 followed by a decline to day 180 in both breeds of pigs, which inosculate the growth rate but is contrary to the pattern of ontogeny of GH mRNA in pituitary. The levels of IGF- 1 in LW male pigs were significantly higher than that of EHL male pigs (P<0.05). This indicates that serum IGF-I directly correlate with growth rate and may also be inv...