Induction of the Expressions of Antioxidant Enzymes by Luteinizing Hormone in the Bovine Corpus Luteum

Luteoprotective mechanisms of luteinizing hormone (LH) involved in the maintenance ofbovine corpus luteum (CL) function have not been completely clarified. Since antioxidantenzymes are well documented as antiapoptotic factors in the CL of many mammals, wehypothesized that the luteoprotective action of LH is mediated by stimulating the localproduction and action of antioxidant enzymes. To test the above hypothesis, in the presentstudy, we examined the mechanisms involved in the luteoprotective actions of LH. Culturedbovine luteal cells obtained from the CL at the mid-luteal stage (days 8–12 of the estrouscycle) were treated with LH (10 ng/ml), onapristone (OP; a specific progesterone receptorantagonist, 100 μM) and diethyldithiocarbamate [DETC; an inhibitor of superoxide dismutase(SOD), 100 μM] for 24 h. LH in combination with or without OP significantly increased themRNA and protein expressions of manganese SOD (Mn-SOD) and catalase (CATA) and SODactivity. While LH alone significantly increased the mRNA and proteinexpressions of SOD containing copper and zinc (Cu,Zn-SOD), OP in combination with orwithout LH significantly decreased the mRNA and protein expressions of Cu,Zn-SOD. Inaddition, Cu,Zn-SOD, Mn-SOD and CATA mRNA expressions were higher at the mid luteal phasethan the other luteal phases. LH in combination with DETC significantly decreasedLH-increased cell viability. The overall results suggest that LH increases cell viabilityby LH-increased antioxidant enzymes, resulting in maintenance of CL function during theluteal phase in cattle.