Cyclic Changes in Utero-Ovarian Blood Flow and Ovarian Hormone Secretion in the Hamster: Effects of Adrenocorticotropin, Luteinizing Hormone, and Follicle-Stimulating Hormone*

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Abstract
These experiments were designed to determine utero-ovarian vein blood flow and ovarian secretion rates and the ability of ACTH, LH, or FSH to modify these parameters in the cyclic hamster. Hamsters were anesthetized with pentobarbital, and polyethylene cannulae were introduced into the utero-ovarian and femoral veins. Five-minute blood samples were collected from the utero-ovarian vein for 50 min. After the second blood sample, ACTH (10 μg/100 g BW), LH (2.5 μg/100 g BW), or FSH (10 μg/ 100 g BW) was injected via the femoral vein. Based on the second 5-min control sample, the pattern of ovarian blood flow and steroid secretion rates during the cycle can be reconstructed. On day 3, utero-ovarian blood flow decreased compared to the day 2 level, but it increased again on day 4. Secretion of estradiol (E2) was low on day 1 (estrus); it increased gradually during the following days and reached a peak on day 4 (proestrus) between 1400–1500 h; thereafter E2 rapidly decreased. The pattern of testosterone (T) secretion paralleled E2 secretion. On days 1 and 2, progesterone (P) secretion was high; it diminished on day 3. There was a further decrease in P on day 4 at 1000 h, but after 1430 h, P increased very rapidly to an even higher level than that found on day 1 or 2. ACTH increased utero-ovarian blood flow on days 1–3. On the morning of day 4, ACTH stimulated E2 and, after 1430 h, it stimulated P secretion. On day 1, ACTH augmented T and P secretion. LH and FSH on day 1 had a slight effect on E2 and P secretion. On day 2, LH and FSH very significantly stimulated E2 and T and slightly increased P secretion. On day 3 and the morning of day 4, the gonadotropins elevated E2, T, and P secretion but were no longer effective on day 4 after 1430 h. At no time did LH or FSH increase utero-ovarian blood flow. ACTH increased utero-ovarian blood flow and ovarian P secretion in adrenalectomized day 1 hamsters. It is concluded that ACTH may directly stimulate ovarian blood flow and, depending on the stage of the cycle, ACTH may participate in ovarian steroid secretion, but its effects are different from LH or FSH.