Characterization of mineralocorticoid and glucocorticoid receptors in pigs: Comparison of Meishan and Large White breeds

Corticosteroids receptors were characterized and compared in central and pe ripheral tissues of two pig breeds, the Meishan (MS) and the Large White (L W) pigs, that display differences in the basal activity and stress-induced reactivity of the hypothalamic-pituitary-adrenal (HPA) axis. In vitro kinet ic experiments on kidney and liver cytosols from adrenalectomized pigs allo wed to identify two distinct corticosteroid receptors referred to as minera locorticoid (MR) and glucocorticoid (GR) receptors. The binding specificiti es were determined for kidney and hippocampal MR and for liver and hippocam pal GR. In hippocampus and peripheral tissues, cortisol showed a greater af finity for MR than for GR. As already described in the dog, mouse and human , dexamethasone and progesterone display a moderate affinity for MR. Putati ve differences in corticosteroid receptors binding capacities and affinitie s were investigated by saturation binding studies in specific regions impli cated in the regulation of HPA axis (hippocampus and pituitary). The MS pig s evidenced higher densities of hippocampal MR, while LW pigs had higher de nsities of pituitary GR. Thus, this study suggests that a difference in the MR/GR balance in hippocampus and pituitary could be implicated in the diff erent HPA activity between MS and LW pigs.