The corpus luteum is a temporary organ that is responsible for progesterone (P4) secretion and is essential for the establishment and maintenance of pregnancy in cattle. Concanavalin A (CONA) is a lectin that was originally extracted from the Jack bean (Canavalia ensiformis) and that interacts with several kinds of cells, including immune cells and luteal cells. The aim of the present study was to evaluate the effects of CONA on the P4 production by bovine steroidogenic luteal cells (LC) in vitro. Luteal cells were collected during the mid-luteal stage (at 10–12 days following ovulation) and processed in the laboratory. Luteal cells were grown for 7 days in a humid atmosphere with 5% CO2, with or without 10% fetal bovine serum (FBS), and were subjected to the following treatments: control: no treatment; CONA (10 μg mL−1); LH (100 μg mL−1); CONA+LH; LH (100 μg mL−1) + prostaglandin F2α (PGF2α; 10 ng mL−1); CONA+LH+PGF2α. Samples of the culture media were collected on Day 1 and Day 7 for P4 quantification. The cells were counted on Day 7 of culture. Differences between treatments were considered statistically significant at P < 0.05. The P4 concentration in the culture media was numerically greater on Day 1 (558.0 ng mL−1) than on Day 7 (25.4 ng mL−1). The P4 concentration in the culture media was numerically greater for treatments with 10% FBS than for the FBS-free treatments, and the presence of CONA decreased LC P4-secreting capacity. This effect required more than 24 h of exposure to CONA to be fully manifested. On Day 1 of culture, CONA had no effect on P4 production of LC cultured in serum-free medium (P > 0.05).The suppressive action of CONA was more pronounced for cultures without FBS. By Day 7 of culture, the effects of CONA on P4 production were readily apparent. In the absence of serum, CONA had a highly significant (P < 0.01) inhibitory effect on basal progesterone production, as well as in the presence of LH or LH + PGF. In the presence of FBS, there was a tendency for decreased P4 in response to CONA in the LH- and the LH + PGF-treated cells (P = 0.090 and 0.085, respectively). The number of the cells present on Day 7 was not affected by the treatments tested (P > 0.05). More studies are required to better understand the effect of CONA on the P4 production of bovine LC.
Financial support from FAPESP is acknowledged: grant no. 2013/00992–3, grant no. 2013/07439–8, and grant no. 2015/01940–2.
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