Cyclooxygenases in Rat Leydig Cells: Effects of Luteinizing Hormone and Aging

Previous studies suggested that increased Leydig cell cyclooxygenase (COX)2 expression may be involved in the reduced testosterone production that characterizes aged Leydig cells. Our objective herein was to further elucidate the relationships among LH stimulation, Leydig cell COX2 and COX1 expression, aging, and testosterone production. Incubation of Leydig cells from young or aged rats with LH or dibutyryl cAMP resulted in increases in both intracellular COX2 protein expression and testosterone production. COX1 expression did not respond to LH or dibutyryl cAMP. Incubation of adult cells with a protein kinase A inhibitor suppressed the stimulatory effects of LH on COX2 and testosterone production. Short-term incubation of Leydig cells with TGF-α or IL-1β also increased COX2 protein levels; IGF-I had no effect. In vivo, LH also was found to stimulate both COX2 and testosterone, but not COX1. As reported previously, COX2 expression was greater in old than in young cells, and old Leydig cells responded to ...