Influence of oxygen tension and substrates on basal and luteinizing hormone stimulated progesterone production and energy metabolism by isolated corpora lutea of adult pseudopregnant rats.

The effect of substrate reduction on in vitro progesterone production by isolated corpora lutea of pseudopregnant rats was studied. Pseudopregnancy was induced by mating adult females with vasectomized males. The rats were killed at different luteal ages and the corpora lutea of pseudopregnancy were identified, dissected free and incubated for 3 h. Six-day-old corpora lutea were incubated in the presence of different oxygen tensions as well as different glucose and amino acid concentrations and basal as well as luteinizing hormone (LH)-stimulated progesterone production was studied. When the oxygen tension was reduced, both basal and LH-stimulated progesterone production was decreased. At 6 and 0 kPa, the stimulatory effect of LH on progesterone production was abolished. Lowering the oxygen tension decreased the levels of adenosine-5'-triphosphate (ATP) in the tissue and increased lactic acid accumulation in the medium. Omitting both glucose and amino acids while maintaining oxygen tension at 100 kPa abolished the stimulatory effect of LH on progesterone production and decreased the levels of ATP. The present study shows that the corpus luteum in vitro is dependent on a high oxygen tension for maintenance of its progesterone production and LH responsiveness. It is suggested that the amount of ATP available is critical to the degree of LH response. Hypoxia increased luteal glycolysis, but this could only marginally compensate for a low oxygen tension.