Steroidogenic acute regulatory protein expression in human granulosa cells exposed to ractopamine in vitro

Abstract

Objective To investigate the effects of ractopamine (RAC) on the expression of steroidogenic acute regulatory protein (StAR) in granulosa cells, aiming to illustrate the possible effects of RAC on steroidogenesis of the ovary. Methods Human granulosa cells were cultured in vitro with the additions of 0 μmol/L RAC (control group), 50 μmol/L RAC, 5 μmol/L RAC, 0.5 μmol/L RAC, 50 μmol/L clenbuterol (CLB) and 50 μmol/L propranolol, respectively. After treatment, granulosa cells were harvested at 0 h, 4 h, 12 h, 24 h and 48 h. Protein and mRNA expressions of StAR were measured by Western blotting and real-time RT-PCR, respectively. Results After exposed to RAC, the changing tendency of StAR in mRNA level was similar to its protein level. StAR remained low level under control condition. RAC and CLB increased StAR expressions, and propranolol decreased its expression. StAR reached a peak after exposed to RAC for 4 h (P=0.000), and underwent a sharp decline after 12 h treatment (P=0.003). Thereafter, StAR restored to the basal level at 24 h (P>0.05). After cocultured with RAC for 4 h, 0.5 μmol/L RAC significantly increased StAR expression (P=0.000). The expression of StAR in 5 μmol/L RAC group was intermediate to 0.5 μmol/L RAC group and 50 μmol/L RAC group. Conclusion RAC increased the expression of StAR in granulosa cells, which may enhance steroidgenesis of the ovary and result in the disturbance of steroid hormone homeostasis. Key words: Ractopamine (RAC); Granulosa cells; Steroidogenic acute regulatory protein (StAR)