Effects of Luteinizing Hormone and Indomethacin on Blood Flow and Steroidogenesis in the Rabbit Ovary

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Abstract
The effects of LH and indomethacin (a prostaglandin synthetase blocker) on ovarian blood flow and steroidogenesis were studied in unanesthetized mature estrous rabbits. Ovarian blood flow was determined by the radionuclide-labeled microsphere technique and plasma progesterone and estradiol 17-β concentrations were measured by specific radioimmunoassays. Ovarian blood flow increased 5-fold as early as 10 min after LH administration (P<0.01). The ovarian hyperemic response to LH was significantly lower in indomethacin-treated rabbits (P<0.05). Rabbits receiving indomethacin had higher ovarian vascular resistance than did untreated rabbits during the control period and at 10 and 30 min after LH administration (P<0.05). A rapid and substantial increase in plasma progesterone, but not estradiol, was observed after LH administration. Ovarian blood flow and peripheral plasma progesterone concentrations were positively correlated (r = 0.69; n = 26; P<0.001) in rabbits without indomethacin treatment. Indomethacin treatment had no effect on resting or post-LH plasma progesterone or estradiol concentrations. These data indicate that indomethacin inhibited the ovarian hyperemic response but not the steroidogenic response to LH. The possible roles of prostaglandins, cyclic AMP and progesterone in mediating LH-induced ovarian hyperemia and steroidogenesis are discussed.
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