Observations on the human corpus luteum: histochemical changes during development and involution

Morphologic studies of the developing, gestational, and involuting corpus luteum show that rapid structural changes occur and that involution is not associated with an appropriate inflammatory response. Histochemical techniques were used to demonstrate several patterns of enzyme activity. The luteunized granulosa cells stained with increasing intensity for lactic dehydrogenase, succinic dehydrogenase, cytochrome oxidase, glucose-6-phosphatase, and 3 beta-hydroxysteroid dehydrogenase, but reactivity for these enzymes dropped markedly with early involution, and staining was never conspicuous in the organizing cavity. Reactions for acid phosphatase, glucosaminidase, galactosidase, glucuronidase, and nonspecific esterase were also present in the developing corpus luteum, but staining decreased more slowly during involution and was prominent in the occasional macrophages in the granulosa and the granulation tissue in the cavity. Staining was moderately intense for all of the enzymes in the corpus luteum of pregnancy. The decrease in activity for these metabolic enzymes confirms the histologic impression of degeneration, but the loss of staining for lysosomal enzymes was more rapid than expected. The latter finding complicates the hypothesis of involution of involution of the corpus luteum as an example of programmed cell death.