Study of the Luteinizing Hormone-Induced Increase of Ovarian Blood Flow During the Estrous Cycle in the Rat

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Abstract
CYF rats were anesthetized on various days of the 4-day cycle and blood samples were collected at 5 min intervals from the ovarian vein before and after i.v. administration of 5 .mu.g/100 g body wt of luteinizing hormone (LH). Ovarian venous outflow, blood pressure and hematocrit were continuously recorded; from the blood samples, response (P) and 17.beta.-estradiol (E2) were determined by radioimmunoassay (RIA). Ovarian blood flow and P secretion showed a parallel increase on Day 1 (etrus), on Day 2 and on the afternoon of Day 4 (proestrous). LH increased ovarian blood flow each day of the cycle together with P and E2 secretion; no relationship was seen between the initial value of hormone secretion and the LH-induced increase of ovarian blood flow. Inhibition of hormone seretion by cycloheximide prevented the LH-induced increase of ovarian blood flow; a decrease of ovarian blood flow parallel with the diminution of hormone secretion was observed. Indomethacin pretreatment abolished the hyperemic effect of LH and partially inhibited the LH-induced increase of hormone secretion. Propranolol blocked the LH-induced increase of ovarian blood flow and blunted the effect of LH on hormone secretion. Apparently, in LH-induced hyperemia, cAMP, prostaglandins, and other vasoactive metabolites related during the process of hormone synthesis and also a .beta.-adrenergic mechanism, are involved in the regulation of ovarian blood flow.