Ethylene glycol monomethyl ether (EGME) or
atrazine induces luteal cell
hypertrophy in rats. Our previous study suggested that EGME stimulates both new and old corpora lutea (CL), while
atrazine stimulates new CL.
Bromocriptine (BRC) is known to suppress the luteolysis in rats. This study investigated the light- and electron-microscopic luteal changes induced by EGME,
atrazine, or BRC. Female rats were treated with EGME (300 mg/kg/day), BRC (2 mg/kg/day), EGME and BRC (EGME + BRC), or
atrazine (300 mg/kg/day) for 7 days. Luteal cell
hypertrophy induced by EGME, EGME + BRC, and
atrazine was subclassified into the following two types: CL
hypertrophy, vacuolated type (CL-V) characterized by intracytoplasmic fine vacuoles, and CL
hypertrophy, eosinophilic type (CL-E) characterized by eosinophilic and abundant cytoplasm. The proportions of CL-V and CL-E were different among the treatments. BRC-treated old CL showed lower proportion of endothelial cells and fibroblasts than normal old CL. Ultrastructural observation revealed that the luteal cells of CL-V contained abundant lipid droplets, whereas those of CL-E in EGME and EGME + BRC groups showed uniformly well-developed smooth endoplasmic reticulum. No clear ultrastructural difference was observed between the control CL and
atrazine-treated CL-E. These results indicate that EGME,
atrazine, and BRC have differential luteal morphological effects.