Progesterone, estrogen, and androgen receptors in the corpus luteum of the domestic cat, Iberian lynx (Lynx pardinus) and Eurasian lynx (Lynx lynx).

In contrast to the species studied, the corpus luteum (CL) of Iberian and Eurasian lynx physiologically persists in the ovary for more than 2 years and continues to secrete progesterone. Such persistent CL (perCL) transition into the next cycle and are present in the ovary together with the freshly formed CL (frCL) of a new ovulation. To date, the mechanisms supporting such CL persistence are not known. We analyzed the potential receptivity of feline CL to sex steroids through mRNA measurements of progesterone receptor (PGR), progesterone receptor membrane components (PGRMC) 1 and 2, estrogen receptor (ESR) 1 and ESR2, G protein-coupled estrogen receptor 1 (GPER1), and androgen receptor (AR). All receptors were present in domestic cat CL during pregnancy and the nonpregnant luteal phase, in frCL and perCL of post-mating Iberian lynx and in perCL of pre-mating Eurasian lynx. Mass spectrometry detected the presence of PGRMC1 protein in frCL and perCL of the Iberian lynx. In both domestic cat and lynx CL, PGR, PGRMC1, and ESR1 proteins were localized in luteal cells by immunohistochemistry. The mRNA levels of PGR, PGRMC1, PGRMC2, ESR1, and AR changed significantly throughout the domestic cat luteal phase. This may indicate involvement of these receptors in the processes of formation, maintenance, and regression of feline CL. In Iberian lynx, expression of PGRMC1, PGRCM2, ESR1, GPER1, and AR was significantly higher in perCL compared with frCL, whereas ESR2 was reversed. High mRNA amounts of these receptors in perCL suggest that physiological persistence of lynx CL may be partly regulated by actions of sex steroids through their nuclear and/or membrane receptors.