The aim of this study was to compare the expression levels of adiponectin receptor 1 and adiponectin receptor 2 mRNAs and proteins in porcine ovaries during four stages (days 2 to 3, 10 to 12, 14 to 16, 17 to 19) of the oestrous cycle and to measure adiponectin plasma concentrations during the same phases of the cycle. Higher mRNA expression of adiponectin receptor 1 was detected in porcine granulosa cells than in corpora lutea and theca cells (P < 0.01). In contrast, higher gene expression of adiponectin receptor 2 occurred in newly developed and mature corpora lutea (P < 0.01). The adiponectin receptor 1 protein content was the highest in corpora lutea isolated on days 2 to 3 of the cycle and was the lowest in theca interna cells (P < 0.01). The profile of adiponectin receptor 2 protein was similar to that of adiponectin receptor 1. Adiponectin plasma concentrations were significantly higher throughout the luteal phase than in the follicular phase (P < 0.01). In conclusion, the presence of adiponectin receptor 1 and adiponectin receptor 2 mRNAs and proteins in the porcine ovary suggests that adiponectin may directly affect ovarian functions through its own specific receptors. The expression of both receptors and adiponectin plasma concentration were dependent on hormonal status related to the stage of the cycle.
Key words: Adiponectin receptors, adiponectin, pig, ovary, oestrous cycleAdiponectin is an adipose-secreted 244-amino-acid protein with 30 kDa molecular weight, which circulates in the blood in the form of a trimer (low molecular weight, LMW), a hexamer (middle molecular weight, MMW) or a multimer (high molecular weight, HMW) (Maeda et al., 1996). Adiponectin exerts its effect by binding to two distinct but structurally related 7-transmembrane receptors, adiponectin receptor 1 (AdipoR1) and adiponectin receptor 2 (AdipoR2).