Oxygen consumption, carbon dioxide production and progestagen secretion in the intact ovary of the day-16 pregnant rat.

Arterial and venous blood gases were measured in the ovary of the Day-16-pregnant rat by a Van Slyke manometric technique. Concurrent observations of progestagen concentrations were also made to determine rates of hormone secretion. The oxygen consumption was 196.5 +/- 28.4 ml/min per kg ovarian tissue (mean +/- s.e.m., n = 8) which is amongst the highest recorded from any organ. Carbon dioxide production was 149.8 +/- 36.6 ml/min per kg ovarian tissue (n = 5) and the respiratory quotient was 0.756 +/- 0.023 (n = 5), indicating that lipids are the major energy substrate used by the ovary. The rates of progestagen secretion were 2.12 +/- 0.37 and 0.42 +/- 0.10 nmol/min per ovary for progesterone and 20 alpha-dihydroprogesterone, respectively, and were not related to oxygen consumption. Less than 1.5% of the oxygen consumed was used in the essential conversion of cholesterol to pregnenolone, the immediate precursor of progesterone.