Bovine ovarian cells have (pro)renin receptors and prorenin induces resumption of meiosis in vitro.

The discovery of a receptor that binds prorenin and renin in human endothelial and mesangial cells highlights the possible effect of renin-independent prorenin in the resumption of meiosis in oocytes that was postulated in the 1980s.This study aimed to identify the (pro)renin receptor in the ovary and to assess the effect of prorenin on meiotic resumption. The (pro)renin receptor protein was detected in bovine cumulus-oocyte complexes, theca cells, granulosa cells, and in the corpus luteum. Abundant (pro)renin receptor messenger ribonucleic acid (mRNA) was detected in the oocytes and cumulus cells, while prorenin mRNA was identified in the cumulus cells only. Prorenin at concentrations of 10(-10), 10(-9), and 10(-8)M incubated with oocytes co-cultured with follicular hemisections for 15h caused the resumption of oocyte meiosis. Aliskiren, which inhibits free renin and receptor-bound renin/prorenin, at concentrations of 10(-7), 10(-5), and 10(-3)M blocked this effect (P<0.05). To determine the involvement of angiotensin II in prorenin-induced meiosis resumption, cumulus-oocyte complexes and follicular hemisections were treated with prorenin and with angiotensin II or saralasin (angiotensin II antagonist). Prorenin induced the resumption of meiosis independently of angiotensin II. Furthermore, cumulus-oocyte complexes cultured with forskolin (200µM) and treated with prorenin and aliskiren did not exhibit a prorenin-induced resumption of meiosis (P<0.05). Only the oocytes' cyclic adenosine monophosphate levels seemed to be regulated by prorenin and/or forskolin treatment after incubation for 6h. To the best of our knowledge, this is the first study to identify the (pro)renin receptor in ovarian cells and to demonstrate the independent role of prorenin in the resumption of oocyte meiosis in cattle.

The roles of prolactin and testosterone in the development and function of granulosa lutein tissue in the rat.

The luteotropic roles of prolactin and testosterone (or estradiol formed in luteal tissue) were investigated in hypophysectomized rats with homografts of granulosa lutein tissue. Using this approach, we could determine the effects of prolactin independently of estrogen, since granulosa lutein tissue does not produce estrogen de novo under these conditions. Luteinizing granulosa cells were expressed from the ovaries of immature pregnant mare's serum gonadotropin-primed Fischer 344 rats 6 h after injection of human chorionic gonadotropin. The cells were transplanted beneath the kidney capsule of adult, hypophysectomized, ovariectomized Fischer 344 recipients, which were treated with hormones daily for 12 or 14 days. In rats without treatment (no hormones, n = 3) and in rats treated with only testosterone (Silastic capsule, n = 6), only small amounts of luteal tissue (less than 5 mg/rat) were found and serum progesterone remained at low concentrations (10 ng or less) throughout the experiment. In contrast, in rats treated either with ovine prolactin (300 micrograms/day, n = 10) or with the combination of prolactin and testosterone (n = 12), serum progesterone increased to 43 ng/ml by Day 8. Beyond Day 8, serum progesterone continued to rise in rats treated with the combination of prolactin and testosterone to reach a mean value of 87 ng/ml by Day 14, and mean homograft wet weight was 49 mg/rat; in rats treated with only prolactin, serum progesterone decreased to 25 ng/ml by Day 14 and homograft wet weight was lower (24 mg/rat). Prolactin and testosterone together stimulated more homograft aromatase activity in vivo than did prolactin alone, but the in vitro production of progesterone was not different.(ABSTRACT TRUNCATED AT 250 WORDS)

Control of gonadotrophin secretion in the female tammar wallaby (macropus eugenii).

A heterologous radioimmunoassay for tammar wallaby FSH, using an ovine FSH antiserum and a human FSH tracer, is described. With this assay concentrations of FSH in plasma of intact female tammars are not detectable except rarely at the time of oestrus. However the assay has proved useful in studies of the control of gonadotrophin secretion in intact male and in ovariectomized tammars. In the female tammar, concentrations of LH and FSH in plasma rose within a few days of bilateral ovariectomy. Ovariectomized tammars respond to a luteinizing hormone releasing hormone stimulus (10 microgram, i.v.) with a prompt release of LH, peak levels of 16.9 +/- 1.4 ng NIH-LH-S19/ml plasma (n = 12) being reached within 25 min of injection. Concentrations of LH and FSH in plasma were reduced to preoperative values in ovariectomized tammars when lutein tissue developed in ovarian cortex grafts autotransplanted under the pouch skin. Ovarian interstitial tissue was not necessary for this effect. After lutectomy during quiescence, the female tammar ovulates again in about 14 days. Injections of progesterone (700 microgram/kg per day, i.m.) for 7 days after the operation did not delay this response, but follicular development and ovulation appeared to be retarded in animals given oestradiol-17 beta (5 microgram/kg per day, i.m.) with or without progesterone.

Effect of corpora lutea grafted under renal capsule on pregnancy in the rabbit.

Implantation of the blastocyst and maintenance of pregnancy were examined by autografting corpora lutea under renal capsule in rabbits. Implantation of the blastocyst did not occur when the corpora lutea were autografted because of small amounts of lutein tissue, low secretory activity of lutein cells, and the period required for functional activity of grafts. Autografts of 4-day-old corpora lutea were capable of maintaining pregnancy after 15 days post coitum, when follicles and interstitial tissue remained intact. Pregnancy was maintained in a limited number of fetuses when 6-day-old corpora lutea were autografted in ovariectomized estradiol-treated does.