Non-luteal Ovarian Tissue Research Articles

Interrelationships among plasma progesterone concentrations, luteal anatomy and function, and placental ontogeny during gestation in a viviparous lizard ( Niveoscincus metallicus: Scincidae)

Plasma progesterone concentrations were measured at six stages of gestation in the viviparous lizard Niveoscincus metallicus. Anatomical and functional parameters of luteal activity were also investigated. The diameter of the corpus luteum (CL) decreased gradually though gestation, as did the diameter of the luteal cells. Major degenerative changes were observed in CLs post-partum. Plasma progesterone concentrations were basal both prior to, and just after, ovulation; a rapid increase occurred in early gestation. Plasma progesterone concentrations remained elevated until late gestation, but fell some 2 weeks before parturition. In vitro production of progesterone was greater in CLs in mid- than in late-gestation, and the addition of prostaglandin F 2α to the incubation medium had no effect on progesterone production. Non-luteal ovarian tissue and adrenals produced progesterone, but at approximately one-tenth the rate of production by CLs. Temporal correlations between the plasma progesterone profile and stages of placental development were also assessed. The rise in plasma progesterone concentrations occurs before differentiation of the chorioallantoic placenta, but progesterone is still high when it degenerates. We conclude that the CLs are the major source of gestational progesterone in N. metallicus.

Glucocorticoids stimulate the accumulation of lipids in the rat corpus luteum.

We investigated the physiological basis for the trophic effect of glucocorticoids in rat corpora lutea in the absence of pituitary gonadotropins. Immature (Day 29) Sprague-Dawley rats were given eCG and hCG to induce the development of corpora lutea and were hypophysectomized on Day 32. Beginning on Day 40, rats received twice-daily s.c. injections of either dexamethasone (dex; 200 microg/rat/day) or vehicle (controls) and then were killed on Day 44. Plasma 20alpha-dihydroprogesterone, a major steroid produced by the corpora lutea, was higher (p </= 0.01) in dex-treated than in control rats (44.5 +/- 2.3 vs. 23.0 +/- 5.6 ng/ml). Dexamethasone treatment increased lipid droplets and lipid in the corpora lutea as revealed by electron microscopy and oil red O staining. Cholesterol esters were higher in corpora lutea of dex-treated rats compared to controls (14.8 +/- 1.1 vs. 2.2 +/- 0.5 microg/mg corpora lutea wet tissue, respectively; p </= 0.05). Another group of hypophysectomized rats was treated with either a high or a lower dosage of corticosterone, both of which caused an elevation to > 2-fold of plasma 20alpha-dihydroprogesterone concentration compared to controls. Glucocorticoid receptor protein (about 92 kDa) was detected in both luteal and nonluteal ovarian tissues in this animal model. These effects of glucocorticoids and the presence of the glucocorticoid receptor raise the possibility of a physiological role for glucocorticoids in the rat corpus luteum.

Mesotocin and Arginine-Vasopressin in the Corpus Luteum of an Australian Marsupial, the Brushtail Possum (Trichosurus vulpecula)

The neuropeptide hormones arginine-vasopressin (AVP) and oxytocin (OT) have been found in the ovarian follicles and corpora lutea (CL) of many eutherian mammals. In ruminants, there is persuasive evidence that luteal OT is involved in luteolysis via stimulation of uterine prostaglandins. However, based on scant evidence, the marsupial ovary has been viewed as being devoid of OT-like and AVP-like peptides. In this study, corpora lutea from the brushtail possum were examined for OT, AVP, and mesotocin (MT) by a combination of reverse phase HPLC, radioimmunoassay, and immunohistochemistry (IHC). Peptides extracted from each of five CL were separated by HPLC and each fraction was assayed for AVP, MT, and OT. Two immunoreactive peaks were found, corresponding to AVP and MT standards. The amount of each peptide was 8.7 ± 2.22 pmol MT/g (mean ± SEM) and 5.7 ± 1.0 pmol AVP/g, respectively. The mean MT/AVP ratio was 1.55 compared to 0.26 for the pituitary, IHC (streptavidin-peroxidase method) of Bouin's-fixed CL showed staining for MT in the cytoplasm of luteal cells which was absent in stromal tissue and nonluteal ovarian tissue. Not all luteal cells were immunopositive and no topographical distribution of stained cells was observed. IHC localization of AVP was not attempted. It was concluded that the CL of the brushtail possum contains low quantities of MT and AVP, which in the case of MT is probably synthesized by the immunochemically staining cells of the CL.

Effects of the ovary, sucking stimulus and season on the pattern of LH and FSH release in the female tammar, Macropus eugenii.

The sequential effects of removal of the corpus luteum, removal of the non-luteal ovary and sucking stimulus and the effects of season of the year on the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH) have been determined in the tammar wallaby, Macropus eugenii. Plasma concentrations of LH and FSH were measured at 15 min intervals for 6 h in eight animals at four successive times in the breeding season (lactational quiescence); (A) while they were intact and lactating, (B) 10 days after removal of the ovary bearing the quiescent corpus luteum, (C) 21 days after bilateral ovariectomy and (D) 21 days after removal of the sucking stimulus, and (E) in the following non-breeding season (seasonal quiescence). Single blood samples were taken twice weekly during lactational quiescence. In the presence of ovarian tissue, basal concentrations of LH were low (0.94 ng mL-1) with pulses of low magnitude (1.3 ng mL-1) and low frequency (1.4 pulses per 6 h). There was no response to luteectomy but all three parameters increased after bilateral ovariectomy. Removal of the sucking stimulus affected the LH pulse frequency but seasonal differences were not evident. The pattern of release of FSH was not pulsatile. There was no response to luteectomy in basal concentrations of FSH but these rose significantly after bilateral ovariectomy (P less than 0.001) in lactational quiescence. There was no effect of removing the sucking stimulus but in seasonal quiescence concentrations were higher. The results indicate that non-luteal ovarian tissue is essential for the negative-feedback effects on LH and FSH secretion, that the pattern of release of LH, but not FSH, is pulsatile, and that there is no marked seasonal change in hypothalamo-hypophysial activity.

Effect of hCG on the 13,14-dihydro-prostaglandin F 2-alpha forming capacity of the ovary after ovulation in PMSG-primed immature female rats

We have examined the change in the ovarian 13,14-dihydro-prostaglandin F 2α (13,14H 2-PGF 2α foorming capacity after the first ovulation induced by injection of pregnant mare serum gonadotropin (PMSG 5 IU, sc) at 26 days of age. After ovulation, the 13,14H 2-PGF 2α forming capacity in the whole ovary (WO) and in non-luteal ovarian tissues (WO-CL) gradually decreased, whereas a rapid decrease of the synthesizing capacity was observed in corpus luteum (CL). The capacity in WO 4 days after ovulation (33 days of age) was markedly stimulated by human chorionic gonadotropin (hCG 10 IU, ip) administration, whereas CL as 33 days of age did not respond to the stimulatory effect of hCG. A single injection of hCG on day 7 after hypophysectomy resulted 12 hrs later in a significant increase in the forming capacity of 13,14H 2-PGF 2α in WO-CL. These results indicate that the 13,14H 2-PGF 2α forming capacity in CL rapidly decreases after the first ovulation and the WO-CL, but not CL, retain the ability to form 13,14H 2-PGF 2α in response to exogenous gonadotropin for a long time.

The nonluteal porcine ovary as a source of angiogenic activity.

Nonluteal ovarian tissue extracts were tested for their ability to stimulate migration and proliferation of cultured bovine capillary endothelial cells. Stimulation of migratory and proliferative activity was found in the 105,000 X g supernatant of homogenates of either whole nonluteal porcine ovaries or isolated theca (follicular walls). Maximal proliferative and migratory activity was obtained with 1-10 micrograms homogenate protein. Neither follicular fluid nor extracts of granulosa cells showed significant activity when tested over a broad concentration range. The proliferative and migratory activities were associated with a heat-labile, nondialyzable, protease-sensitive fraction that was soluble in 40%, but not 60% (NH4)2SO4. The tissue extracts that effectively stimulated growth and migration of capillary endothelial cells in vitro also stimulated the formation of new capillary blood vessels in an angiogenesis assay performed on chick chorioallantoic membranes.

A quantitative relationship between conceptus number and ovarian steroid dehydrogenase activity in pregnant rats.

The effects of a conceptus-derived substance on the activity of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and 20 alpha-HSD in the ovary were studied in the rat. On day 7 of pregnancy (day 1 = insemination), rats were laparotomized and the desired number of conceptuses was aspirated from the uterus; thus, rats carrying one, two, three, four, five to seven or eight to ten conceptuses were prepared. They were autopsied on day 15 and 3 beta-HSD and 20 alpha-HSD activity in the corpus luteum (CL) or non-luteal ovarian tissue ( NLO ) was determined. Conceptus number was directly related to 3 beta-HSD and inversely related to 20 alpha-HSD activity in the CL. The serum progesterone level and CL weight were also directly related to conceptus number. Neither 3 beta-HSD nor 20 alpha-HSD activity in the NLO was affected by conceptus number. These results indicated that 3 beta-HSD and 20 alpha-HSD in the CL are probably regulated by placental hormone secreted in proportion to the number of conceptuses; in the NLO these enzymes may be controlled by a different mechanism.

Luteal adenylyl cyclase does not develop sensitivity to desensitization by human chorionic gonadotropin in the absence of nonluteal ovarian tissue.

There is evidence suggesting that the mere presence of a hormone-responsive adenylyl cyclase system in a tissue may not be sufficient for desensitization to occur since phosphorylation reactions might also be involved. The purpose of this study was to determine if luteal tissue in the absence of other ovarian tissues would desensitize to human CG (hCG). One or both ovaries were removed from rabbits 5 h before hCG-induced ovulation and the periovulatory follicles were transplanted underneath the kidney capsule where they formed ectopic corpus luteum [or corpora lutea (CL)]. Rabbits which were bilaterally ovariectomized received estradiol implants at the time of ovariectomy to maintain control serum estradiol concentrations. On day 7 of pseudopregnancy, the rabbits were injected with saline (control) or with 75 IU hCG and were killed 24 h later at which time ovarian and ectopic CL progesterone content and adenylyl cyclase activity were assessed. As expected, in ovarian CL there was decreased LH-responsive adenylyl cyclase (69% relative to control) and a correspondingly decreased luteal progesterone content (40% relative to control). In the same rabbits, the ectopic CL showed much the same pattern of response as the ovarian CL but perhaps to a slightly lesser extent (decreases relative to control of 59% in adenylyl cyclase response to LH and 29% in progesterone content). However, in rabbits with ectopic CL only, the luteal tissue showed no change either in hormone-responsive adenylyl cyclase activity or in progesterone content. Similarly, binding of radiolabeled hCG to luteal membranes 24 h after hCG was almost totally absent in ovarian CL, was decreased by 50% in ectopic CL with one ovary present, and was unaltered in ectopic CL of bilaterally ovariectomized rabbits. These data suggest that nonluteal ovarian tissue may be required for the induction in CL of the appropriate protein kinases for the proposed phosphorylations involved in adenylyl cyclase desensitization.

In vivo and in vitro ovarian steroidogenesis in the long term hypophysectomized rat.

Ovarian steroidogenesis in the hypophysectomized rat was studied using immature female rats pretreated with 5 IU PMS at 30 days of age and hypophysectomized between 0900–1000 h on either day 32 (before ovulation; group without corpora lutea) or day 33 (the day of ovulation; group with corpora lutea). Serum levels of progesterone (P) and estradiol-17β (E2) in the group with corpora lutea were consistently low, but detectable, from day 5–40 after hypophysectomy, whereas serum 20α-dihydroprogesterone (20α-OHP) and testosterone (T) remained relatively high. However, serum P, 20α-OHP, T, and E2 in the animals without corpora lutea were significantly less on days 5–20, suggesting that these hormones were primarily secreted from corpora lutea but not nonluteal ovarian tissues. The steroidogenic capacity of the corpora lutea and nonluteal ovary at different times after hypophysectomy was assessed by incubation for 2 h in Krebs-Ringer bicarbonate. Five to 40 days after hypophysectomy, the corpora lutea in vitro pr...

Peripheral blood and ovarian levels of sex steroids in the lactating rat.

Changes in progesterone (P), 20α-dihydroprogesterone (20α-OHP), testosterone (T) and estradiol-17β(E2) in peripheral blood, in corpora lutea (CL) of pregnancy and lactation and non-luteal ovarian tissues (NLO), and serum levels of LH, FSH and prolactin (PRL) were determined by radioimmunoassay in lactating rats nursing 8 pups. CL of pregnancy and lactation and NLO were removed at various days after post-partum ovulation (Day 0 of lactation=day of parturition).Serum E2 remained low until Day 10 of lactation followed by a slight increase from Days 12 to 21. Serum T was unchanged throughout lactation. Low levels of T and E2 in NLO were observed until Day 12, followed by a gradual increase on Day 15 and onward. These changes correlated with low levels of serum LH from Days 2 to 12 and a return to basal levels on Days 15 to 21. Throughout lactation serum FSH remained at basal levels corresponding to diestrous values during the estrous cycle. High levels of serum PRL were observed from Days 4 to 10. Serum levels of P reached maximal values between Days 8 and 10 and decreased after Day 12. Changes in serum 20α-OHP were inversely related to serum P throughout lactation. The CL of pregnancy contained large amounts of 20α-OHP and small amounts of P on Days 1 and 2 followed by an abrupt decline until Day 21. On the other hand, a marked increase in content and concentration of P in the CL of lactation occurred between Days 6 and 12 followed by a gradual decline by Day 21. Content and concentration of 20α-OHP in the CL of lactation increased progressively from Day 1 to 21.These findings indicate that the CL of pregnancy secrete a large amount of 20α-OHP and a small amount of P during the early stages of lactation. Thereafter, the CL of lactation markedly increase their ability to secrete P. High levels of P and PRL during the first half of lactation along with strong suckling stimuli may be involved in the suppression of follicular development, presumably by lowering basal levels of serum LH.

In vivo and in vitro ovarian steroidogenesis in the pregnant rat.

The interrelationship between follicular and luteal function during pregnancy in the rat was examined by in vivo and in vitro methods. Corpora lutea (CL) and nonluteal ovarian tissues (NLO) were removed on Days 2 to 22 (at 2 day intervals) (day sperm-positive = Day 1 of pregnancy), and incubated separately for 2 h to determine the production rate of steroids. Changes in progesterone (P), 20a-dihydroprogesterone (20a-OHP), testosterone (T), and estradiol-1713 (E2) in peripheral blood, CL, and NLO, and levels of LH and FSH in serum and pituitary were measured by radioimmunoassay. A marked decline in the in vitro production rate of E2 and T in NLO occurred between Days 14 and 18 followed by an abrupt increase on Days 20 and 22. These changes correlated with the levels of serum LH between Days 14 and 22. Serum FSH also declined on Day 16 but returned to basal levels by Day 18. Despite the fall in N_LO production of E,, serum E2 started to increase on Day 14 with a progressive rise continuing until term. A marked increase in lutes! content of E2 occurred on Day 16 and continued until Day 22, whereas in vitro production of E2 by CL declined from Day 14 onward. Serum T also began to increase on Day 14 with the peak attained between Days 18 and 20, paralleling the rising E2 levels. In vitro production of luteal T increased on Day 12 with peak values present between Days 16 and 20, paralleling the pattern of serum T. Maximal values of serum P occurred between Days 14 and 16 and decreased after Day 18. In vitro production of luteal P increased abruptly on Day 4, with peak values on Day 10 and a decline by Day 16. There was a second peak in in vitro production of P on Day 22, although serum and luteal levels of P were already low. Changes in serum levels of 20o-OHP and its in vitro production rate were inversely related to changes in P throughout pregnancy. These findings indicate that at the end of pregnancy the CL produce large amounts of P in vitro after functional luteolysis has occurred in vivo. The high levels of P during midpregnancy may be involved in the suppression of follicular maturation, probably by lowering basal levels of serum LH. Furthermore, between Days 14 and 18, secretion of T and E2 represents proportionally more luteal than follicular sources of the hormones in the pregnant rat.

Effect of neutralization of endogenous follicle stimulating hormone (FSH) or luteinizing hormone (LH) on ovarian lipids in the hamster: a histochemical and biochemical evaluation.

The effect of neutralizing FSH or LH on ovarian lipids in the cycling hamster was studied. In the normal cycling hamster on the day of proestrus, histochemical examination revealed the presence of sudanophilic lipids in the granulosa cells of the follicles and in the interstitium. A clear reduction in the intensity of lipid staining was observed on proestrus in the ovary of hamsters treated with FSH antiserum on the previous proestrus. Similar treatment with antiserum to LH, on the other hand, caused an accumulation of lipids in these structures. Estimation of the free and esterified fractions of cholesterol and triglycerides in the nonluteal tissue of the ovary of hamsters on proestrus following treatment with FSH antiserum on the previous proestrus revealed a significant reduction in all 3 lipid components. Even a short term deprivation of FSH caused a similar reduction in these lipids in the ovary. In contrast, treatment with LH antiserum either on the previous proestrus or on the previous day (diestrus-2) resulted in an enhancement in esterified cholesterol and triglycerides, while it caused a reduction in the free cholesterol fraction of the ovary on proestrus.It is suggested that though treatment with antisera to either FSH or LH causes a disruption in follicular maturation, their effect on lipid metabolism is different. A positive role for FSH and LH in maintaining normal sterol and triglyceride levels in the nonluteal ovarian tissue of cycling hamster is indicated.

Measurement of FSH in the ovarian tissue by radioimmunoassay: Correlation to serum FSH levels and follicular development in the hamster

A method is described for monitoring the concentration of endogenous receptor-bound gonadotropin in the ovarian tissue. This involved development of a radioimmunoassay procedure, the validity of which for measuring all of the tissue-bound hormone has been established. The specificity of the method of measurement was indicated by the fact that high levels of FSH could be measured only in target tissue such as follicles, while non-target organs showed little FSH. Using this method, the amount of FSH in the non-luteal ovarian tissue of the hamster at different stages of the estrous cycle was quantitated and compared with serum FSH levels found at these times. No correlation could be found between serum and tissue FSH levels at all times. On the morning of estrus, for example, when the serum level of FSH was high, the ovarian concentration was low, and on the evening of diestrus-2 the ovary exhibited high concentration of FSH, despite the serum FSH concentration being low at this time. The highest concentration of FSH in the ovary during the cycle was found on the evening of proestrus. Although a large amount of this was found in the Graafian follicles, a considerable amount could still be found in the ‘growing’ follicles. Ovarian FSH concentration could be considered to be a reflection of FSH receptor content, since preventing the development of FSH receptors by blocking initiation of follicular development during the cycle resulted in a decrease in the concentration of FSH in the ovary. The high concentration of FSH in the ovary seen on the evening of diestrus-2 was not influenced either by varying the concentration of estrogen or by neutralization of LH. Neutralization of FSH on diestrus-2, on the other hand, caused a drastic reduction in the ovarian LH concentration on the next day (i.e. at proestrus), thus suggesting the importance of FSH in the induction of LH receptors.

In vitro Steroidogenesis in Corpora Lutea and Nonluteal Ovarian Tissues of the Cyclic Hamster

The steroidogenic capacity of the luteal and nonluteal ovarian (NLO) compartments was assessed during the hamster estrous cycle by 2 h in vitro incubations in Kreb’s Ringer bicarbonate. On Day 1 of the estrous cycle (Day I is the day of ovulation), the most striking results obtained from the incubation of NLO and corpora lutea (CL) were the inabilities of these 2 compartments to synthesize significant amounts of progesterone (P) despite serum P levels of 6 ng/ml. In fact, the NLO lost P at a rate of 2.5 ng/mg/h, whereas the CL failed to synthesize significant quantities of P. These results were further substantiated by incubations of intact ovaries (CL + NLO) on Day 1 which revealed a significant net loss of P (0.80 nglmg/h). P levels in NLO (9.0 ng/mg) were higher on Day 1 than on any other day of the cycle and CL on Day 1 contained approximately 14.0 ng P/mg. Also on Day 1, NLO syntheses of androstenedione (A), testosterone (T), estrone (E1) and estradiol (E2) were at baseline levels compared to synthesis on other days of the cycle. The Day 1 results suggest that a major portion of the large quantity of P contained within the ovary prior to incubation was converted to steroids other than those measured. Day 1 CL failed to syn’ thesize significant quantities of P; this poor steroidogenic capability may result from their incomplete luteinization. On Day 2 of the cycle, a significant upswing in production of P and A by NLO and CL was accompanied by increased production rates of E1 and E2 by NLO. However, T production by NLO and CL was unchanged from Day 1. Corpora lutea did not produce estrone or estradiol on any day. Luteal regression which occurred by Day 3 was characterized by a significant decline of P in CL and serum. The production rate of P by CL was also significantly lower on Day 3 than on Day 2. Concomitant with luteal regression was an increase in the production rate of E1 and E, by NLO without changes in NLO production of P and T. These changes were paralleled by increased concentrations of E1 and E2 in serum and NLO. Steroid production on Day 4 was similar to that on Day 3, except that A production was higher on Day 4 than at any other time, however, serum A concentration remained unchanged from Day 3. The results of this study indicate that in vitro, the Day 1 hamster ovary (CL and NLO) exhibits a low level of steroidogenic activity; thereafter, an upswing in steroidogenic activity was observed in both ovarian compartments (CL and NLO) until the demise of the CL on Day 3.

Ability of an Extract of Pig Corpus Luteum to Inhibit Binding of 125l-Labeled Human Chorionic Gonadotropin to Porcine Granulosa Cells

SummaryPorcine corpus luteum tissue contains an inhibitor of binding of iodinated human chorionic gonadotropin to porcine granulosa cells. The inhibitor was present in the 1000, 30,000, and 105,000g supernatants of the corpus luteum but not in those of nonluteal ovarian tissue, granulosa cells, lung, or heart tissue. The inhibitor appeared only after storage in the freezer for from 1.5 to 11 weeks. Freezing heart, lung, or nonluteal tissue for a comparable time period did not lead to an increase in inhibitory activity.

Synthesis of 17β-Estradiol by Isolated Ovarian Tissues of the Pregnant Rat: Aromatization in the Corpus Luteum

Corpora lutea from pregnant rats were incubated to determine their ability to produce 17beta-estradiol and to aromatize testosterone in vitro. Corpora lutea and non-luteal ovarian tissues were removed from rats on days 7, 15, and 22 of pregnancy, and these tissues were immediately frozen or incubated separately in medium 199 at 37 C in an atmosphere of 95% O2-5% CO2 for 4 h. 17Beta-Estradiol in tissue and medium were quantified by a highly specific radioimmunoassay. The estradiol content ivnariably increased in non-luteal tissues during incubation, while it decreased or remained the same in incubated corpora lutea. The synthesis in non-luteal tissues, which was 18 to 400-fold greter. The incubation of corpora lutea (5 to 25 mg of tissue) with testosterone (200 ng) on days 7, 15, and 22 of pregnancy resulted in a mean accumulation of 17beta-estradiol in medium of 2.5 x 103 pg/mg tissue, compared with a mean value of 6 pg/mg for luteal tissue removed from the same ovaries and incubated without testosterone. The incubation of corpora lutea from 15-day pregnant rats with (7alpha-3H)-testosterone resulted in 15% conversion to presumptive (7alpha-3H)17beta-estradiol, which was isolated identically to estradiol isolated for radioimmunoassay. Recrystallization to constant specific activity revealed a high degree of radiochemical purity (75%) of the isolated (3H)estradiol. Rat diaphragm muscle and rabbit corpora lutea did not aromatize testosterone to 17beta-estradiol in amounts detectable by radioirpora lutea in vitro is virtually diol by non-luteal ovarian tissues. However,the corpora lutea show a striking capacity to aromatize testosterone, which might explain the high estradiol content of the rat corpora lutea during pregnancy. The physiological significance of this aromatizing system and of 17beta-estradiol in the corpus luteum is unknown but may be related to the luteotropic action of estradiol in the pregnant rat.

Studies on Luteolysis: Effect of Antiserum to Luteinizing Hormone on Sterols and Steroid Levels in Pregnant Hamsters

The effect of luteinizing hormone antiserum (LH A/S) on sterol and steroid levels in luteal and non-luteal ovarian compartments, and on serum steroid levels of pregnant hamsters, was studied. Injection (ip) of 0.1 ml of LH A/S on day 7 caused termination of pregnancy and morphological regression of the corpus luteum (CL) within 18-20 h of treatment, whereas LH-free non-immune serum had no effect. Within 3 h of administration of LH A/S the luteal progesterone levels fell from a control value of 36.0 +/- 2.4 to 15.6 +/- 3.4 ng/mg, and estrogen from a control value of 20.8 +/- 3.4 to 12.2 +/- 1.5 pg/mg. By 12 h progesterone had dropped to 7.3 +/- 0.3 ng/mg whereas estrogen was undetectable by radioimmunoassay. Serum progesterone fell in 3 h from 5.53 +/- 0.39 to 3.15 +/- 0.26 ng/ml whereas estrogen fell from 172 +/- 26 to 123 +/- 9 pg/ml. The progesterone content of non-luteal ovarian tissue dropped in 3 h from 1.06 +/- 0.01 to 0.47 +/- 0.06 ng/mg and estrogen from 115.0 +/- 1.5 to 11.0 +/- 0.65 pg/mg. Both progesterone and estrogen were undetectable at 24 h. In the CL, free cholesterol concentration did not change significantly after A/S treatment, while esterified cholesterol increased from 2.82 +/- 0.14 to 4.14 +/- 0.25 mug/mg within 6 h and 5.52 +/- 0.17 mug/mg by 12 h. The results suggest that LH plays a critical role in the maintenance of CL of early pregnancy in the hamster and that deprivation of LH, even for periods as short as 3 h, significantly influences steroid production. The accumulation of cholesterol esters following LH-deprivation suggests that loss of cholesteryl esterase activity could be one of the events leading to luteolysis.

The postpartum gonadotrophin surge in the rat depends upon the presence of nonluteal ovarian tissues.

The role of nonluteal ovarian hormones in the surge of luteinizing hormone (LH) which occurs in the hours following parturition was studied in 3 groups of rats. Ectopic corpora lutea were established in rats by autotransplantation of follicles beneath the kidney capsule on the evening of proestrus (Day 0). Group 1 rats had ectopic corpora lutea Group 2 had ectopic corpora lutea and a single ovary from which corpora lutea had been removed and Group 3 had a single intact ovary and were w ithout corpora lutea. All rats carried pregnancies for 22-24 days and the pups were removed after delivery to prevent suckling. Blood samples were obtained by heart puncture at intervals after the onset of delivery. Surges of LH (greater than 1.0 mcg/ml serum) were detected at 4.5-9 hours after delivery in rats in Groups 2 and 3. LH surges were absent in rats in Group 1 as late as 18 hours after delivery. Mean LH concentration was 100 + or -17 ng/ml. Prolactin levels were elevated only in animals that showed an LH surge (except 1). The data suggest th at parturition and associated withdrawal of luteal and placental hormones permit postpartum gonadotropin surge. However the necessary stimulus for the LH surge must be provided by the nonluteal ovarian hormones.

Role of non-luteal ovarian tissues in the maintenance of pregnancy.

ABSTRACT The maintenance of pregnancy by daily injections of progesterone from the time of nidation to term has been studied in rats following removal of the ovaries, removal of the active corpora lutea or pharmacological suppression of the corpora lutea with ergocornine. Progesterone was able to maintain normal embryogenesis following ergocornine or removal of corpora lutea but not in ovariectomized rats. This suggests that the non-luteal tissues of the ovary secrete hormones essential for the maintenance of gestation. Other observations include a high pre-implantation loss of embryos and an increase in the average conceptus weight not correlated with the litter size following removal of corpora lutea or of the ovaries. It is concluded that pregnancy is maintained by the combined activities of luteal and non-luteal ovarian tissues.

Secretion of the prenidation estrogen surge by the nonluteal ovarian tissues.

Two methods have been used to suppress the secretion of the corpora lutea of pregnancy in pregnant rats, surgical extirpation and ergocornine injection. These treatments were applied before nidation. Ovum implantation occurred at the normal time. It is concluded that the surge of estrogen secretion which determines the time of nidation is secreted from the nonluteal tissues of the ovary, probably the follicles. (Endocrinology 85: 177, 1969)