Figure 1: The pap smear shows that the control rat is in the diestrus (full of small leukocytes) stage (A). Hematoxylin-eosin staining reveals that the ovaries of the control animal have a number of marginal cysts (B). Normal follicular activity is prominently observed in the shortest period (3 days) with L-arginine treatment at a low dose (5 mg/kg), and the number of cysts is reduced (C). Higher doses (D: 25 mg/kg, E: 50 mg/kg) have no significant effect on cyst reduction, even in short periods. (Other periods are not shown due to lack of significant responses). C: Cyst; GF: Graafian follicle. Scale bar is 50 μm.