An enzymologic study of corpora lutea in early pregnant rats treated with abortifacient agents.

Luteal metabolism was investigated in corpora lutea of early pregnant rats treated with four abortifacient agents. In corpora lutea of rats treated with prostaglandin F2alpha or of rats 1 day postpartum, glucose-6-phosphate dehydrogenase (G6PDH) activity increased 140 to 170% and 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD) was activated to significantly high levels, whereas malic enzyme activity decreased to 29% of control values. In aminoglutethimide-treated rats, the activities of G6PDH and malic enzyme decreased, while 20alpha-HSD activity was maintained at a very low level. With the increased dose, complete abortion was observed. In corpora lutea of these aborted rats, 20alpha-HSD was activated moderately and G6PDH values were slightly higher than control values, whereas malic enzyme activity fell to lower levels. All rats treated with clomiphene citrate aborted within 63 hours after the last injection. The activities of G6PDH, malic enzyme, and ATP citrate lyase in these corpora lutea decreased to 66, 68, and 72% of control levels, respectively; 20alpha-HSD activity was maintained at a very low level, and activities of 3beta-hydroxysteroid dehydrogenase, 6-phosphogluconate dehydrogenase, and pyruvate kinase were not appreciably altered. These findings indicated that, at the beginning of luteolysis and fetal resorption, the activities of steroidogenic enzymes decreased and 20alpha-HSD was not yet activated. Therefore, we could gauge the early changes of luteolysis by measuring the activities of G6PDH, MALIC ENZYME, AND ATP citrate lyase as well as 20alpha-HSD.