Effect Of Transportation On The Expression Of Genes Related To Endogenous Opioid Peptide Function In Hypothalamus And Pituitary Of Growing Pigs

In order to study the regulation mechanism of pig central neuro-endocrinology under the transport stress, twelve healthy Erhualian (EHL, Hal^NN) male growing pigs and twelve healthy Pietrain (PIE, Halⁿⁿ) male growing pigs at the body weight of 19.89±1.58 kg were allocated randomly into the EHL control group, EHL transport group, PIE control group and PIE transport group respectively. The transport groups were subjected to 2 hrs road transportation. 15 min after the transportation, pigs from both control and transport groups were sampled at the same time. Semi-quantitative RT-PCR was used to determine: (1) the abundances of mRNA for proopiomelanocortin (POMC) and mu opioid receptor (MOR) in the different tissues of EHL control group; (2) the affect of 2 hrs transport stress on the genes expression of POMC, prohormone convertase 2 (PC2), MOR and glucocorticoid receptor (GR) in the hypothalamus, POMC, prohormone convertase 1 (PC1), PC2, MOR and GR in the pituitary.1 The distribution of POMC and MOR mRNA in different tissues of pigThe expression of POMC mRNA was determined in pituitary, hippocampus, liver, adrenal gland, hypothalamus, as well as in longissimus dorsi muscle. The abundance of POMC mRNA was shown as the decreasing order in pituitary, hippocampus, liver, adrenal gland, hypothalamus and longissimus dorsi muscle.The expression of MOR mRNA was determined in pituitary, hippocampus, liver, adrenal gland, hypothalamus, as well as in longissimus dorsi muscle. The abundance of MOR mRNA was shown as the decreasing order in hypothalamus, liver, hippocampus, adrenal gland and pituitary, and longissimus dorsi muscle.2 Effect of transport stress on the expression of genes related to EOP function in hypothalamus and pituitary of growing Hal^NN EHL pigsAfter 2 hrs transportation, the hypothalamic POMC mRNA abundances in EHL transport group was 72.36% higher than that in control group (P＜0.01); PC2 mRNA tended to be higher in transport group (P＞0.05); MOR mRNA abundances in transport group was 24.62% higher than that in control group (P＜0.05). However, no significant difference was observed in GR mRNA expression (P＞0.05). These results indicated that 2 hrs transportation made the genes expression changed related to EOP system in the hypothalamus of growing Hal^NN EHL pigs, and the hypothalamic EOP system took part in regulating transport stress response.In the pituitary, GR mRNA in transport group tended to be lower than that in control group (P=0.08). The abundances of POMC, PC1 and MOR mRNA had no significant difference between two groups; but transport stress made the PC2 mRNA significant decrease (P＜0.05), PC2 mRNA abundances in transport group (0.74±0.06) was 19.73% lower than that in control group (0.93±0.04).3 Effect of transport stress on the expression of genes related to EOP function in hypothalamus and pituitary of growing Halⁿⁿ PIE pigsAfter 2 hrs transport stress, the hypothalamic POMC mRNA abundances had no significant difference between two groups (P＞0.05); PC2 mRNA abundances in transport group was significantly higher than that in control group (P＜0.05); MOR mRNA abundances had no significant difference between transport group and control group (P＞0.05), neither in GR mRNA expression (P＞0.05).In the pituitary, GR mRNA in transport group was no significantly different, comparing with that in control group (P＞0.05). The abundances of POMC, PC1 and MOR mRNA had no significant difference between two groups (P＞0.05); but transport stress made the PC2 mRNA significant decrease (P＜0.05), PC2 mRNA abundances in transport group was 48.40% lower than that in control group.These results indicated that (1) the abundance of POMC and MOR mRNA had tissue difference in growing EHL pig; (2) the level of POMC, MOR and GR mRNA were no significantly affected after 2 hrs transport stress, but PC2 mRNA abundance was significantly decreased; (3) 2 hrs transportation made the genes expression changed related to EOP system in the hypothalamus of growing Hal^NN EHL and Hal^NN PIE pigs, and the hypothalamic EOP system took part in regulating transport stress response. (4) the response of hypothalamic EOP system to transportation stress was more sensitive in growing Hal^NN EHL pigs than that in growing Hal^NN PIE pigs, and this may contribute to the reasons of the breeds difference in stress response.