Evaluation of adrenocorticotropin regulated glucocorticoid synthesis pathway in adrenal of different breeds of pigs

Variation in the hypothalamic-pituitary-adrenal (HPA) axis has been reported in numerous species and has been implicated in the differences of adrenal response to ACTH observed between different pig breeds; however, few studies have been conducted in indigenous Chinese pig breeds. The present study, we have investigated ACTH regulated adrenal glucocorticoid synthesis pathway in five breeds of pig: four indigenous Chinese pig breeds (Bama, Huanjiang, Lantang and Ningxiang) and an alien breed (Landrace) which were under same conditions. As a result, the ACTH concentrations were significantly greater than others in Lantang and significantly lesser than others in Bama, and they were also significantly lesser in Ningxiang than in Landrace. On the contrary, the cortisol concentrations in Lantang were significantly lesser than those in Bama. According to the opposite pattern on serum concentrations of ACTH and cortisol, Bama, Lantang and Landrace were chosen for further research. The protein contents of MC2R and StAR in adrenal were significantly lesser in Lantang than in Landrace, and the MC2R levels of Bama were also significantly greater than those of Lantang. The StAR protein levels in Bama were greater than those in Lantang as well, and this difference approached significance. Compared with Landrace, the number of mRNA transcripts for StAR, POMC and PC1 in Lantang were significantly lesser than in Landrace. These results indicate Lantang exhibited lower cortisol synthesis capacity under a relatively greater serum ACTH concentration, while Bama and Landrace exhibited just the opposite. These results at least reveals ACTH regulated glucocorticoid synthesis pathway in adrenal of different breeds of pigs, which can provided reference data for further breeding work.