Search PubMed⌕ Search

Biomedical subjects

R L Stouffer

Publications and source records attributed to R L Stouffer.

At least 91 records · Page 5Linked to original sources
PubMed1991

Current understanding of the corpus luteum in women and nonhuman primates.

Despite the important advances detailed in this review, our understanding of the factors and mechanisms controlling the function of the corpus luteum in the menstrual cycle is rudimentary. Luteolysis remains a mystery. As the activities and interactions between different cell types in the corpus luteum are defined and the role(s) of endocrine, paracrine, and autocrine factors are elucidated, however, we should begin to understand the "self-destruct" process at the end of the cycle. As cellular and molecular approaches combine with physiologic techniques, new information will be available to address the clinical issues of luteal dysfunction which perplex us all.

Animals↗
PubMed1991

Differential uptake of fluorescent-tagged low density lipoprotein by cells from the primate corpus luteum: isolation and characterization of subtypes of small and large luteal cells.

Three enriched populations of cells [C alpha, non-steroidogenic cells less than or equal to 15 microns in diameter; R1, small (less than or equal to 15 microns) steroidogenic cells; and R3, large (greater than 20 microns) steroidogenic cells] have been isolated from the macque corpus luteum using flow cytometry based on light scatter properties. To determine whether the cell populations differ in their ability to bind and internalize low-density lipoprotein (LDL), collagenase-dispersed cells were prepared from the corpus luteum of rhesus monkeys at midluteal phase of the menstrual cycle. Cells were incubated in Hams F-10 medium containing fluorescent-tagged LDL (DiI-LDL). Optimal labeling occurred at 10 micrograms DiI-LDL/10(6) cells.ml incubated for 20 min at 37 degrees C. Labeled cells were analyzed and sorted by flow cytometry based on light scatter and fluorescence. Only 8.2 +/- 1.0% (n = 10) of C alpha cells exhibited fluorescence intensity greater than the autofluorescence of unlabeled cells. In contrast, 52.3 +/- 3.4% of R1 cells and 83.9 +/- 2.3% of R3 cells were fluorescent. Uptake of DiI-LDL was competitively inhibited when cells were conincubated with either unlabeled monkey or human LDL, but human high-density lipoprotein and very low-density lipoprotein were less effective. Progesterone (P) production by fluorescent [DiI-LDL(+)] R1 luteal cells was increased (P less than 0.001) in the presence of pregnenolone, but not human (h) CG, consistent with earlier results for the R1 population. Surprisingly, basal P production by the nonfluorescent [DiI-LDL(-)] R1 cells was similar to that by fluorescent cells and was stimulated by both hCG (P less than 0.01) and pregnenolone (P less than 0.001). Basal P production by DiI-LDL(+) R3 cells was nearly 10-fold greater than that by DiI-LDL(-) R3 cells. P secretion by both DiI-LDL(+) and (-) R3 cells was stimulated by hCG (P less than 0.01) and pregnenolone (P less than 0.001). DiI-LDL(-) C alpha cells produced barely detectable levels of P, but DiI-LDL(+) C alpha cells secreted P at levels similar to R1 cells. We conclude that: 1) multiparameter (light scatter and fluorescence) cell sorting is a useful method for separating enriched populations of cells from the corpus luteum; and 2) small and large luteal cell populations from the macaque corpus luteum consist of subtypes of steroidogenic cells that differ in lipoprotein uptake and/or gonadotropin sensitivity.

Animals↗
PubMed1991

Titrating luteinizing hormone surge requirements for ovulatory changes in primate follicles. I. Oocyte maturation and corpus luteum function.

The amplitude and duration of the midcycle LH surge required for ovulatory maturation of the follicle and its enclosed oocyte in primates are unknown. To titrate periovulatory LH requirements, female rhesus monkeys received human gonadotropins (FSH with/without LH) for 9 days beginning at menses to promote the development of multiple preovulatory follicles. The next day, animals (n = 4-6/group) received: 1) no ovulatory stimulus; 2) 1000 IU hCG, im; 3) one injection of 100 micrograms GnRH, sc (GnRH-1); 4) three injections of GnRH (GnRH-3) at 3-h intervals (0800, 1100, and 1400 h); or 5) two injections of 50 micrograms GnRH agonist (GnRHa), sc, 8 h apart (0800 and 1700 h) to induce ovulatory maturation. Follicles were aspirated 27 h after the hCG or initial GnRH/GnRHa injection or on days 8 and 10 in animals receiving no ovulatory stimulus. Nuclear maturity of oocytes was evaluated as a marker for reinitiation of meiosis. Estradiol and progesterone levels were determined in daily serum samples by RIA. Levels of LH(-like) bioactivity were measured at selected intervals after hCG injection and within 24 h of GnRH/GnRHa treatment. In all groups, estradiol continuously rose to similar peak levels on day 10. The hCG treatment markedly elevated circulating LH-like bioactivity for up to 3 days. In GnRH-1, bioactive LH increased to 433.1 +/- 170.2 ng/mL (mean +/- SEM; n = 3) within 1-2 h, but then decreased to baseline (4.9 +/- 1.5 ng/mL) within 6 h. GnRH-3 and GnRHa treatment extended the interval of elevated bioactive LH to 8 and 14 h, respectively. There was no difference in the peak levels of LH(-like) bioactivity reached after hCG, GnRH, or GnRHa injection. Functional luteal phases were absent in monkeys receiving no ovulatory stimulus, whereas hCG treatment increased progesterone levels to 101 +/- 9 nmol/L (n = 6) and elicited functional luteal phases of 11.8 +/- 0.4 days. In contrast, only one animal in the GnRH/GnRHa groups (i.e. one GnRH-3 monkey) displayed elevated progesterone levels in the luteal phase. Of the total cohort of oocytes aspirated from follicles, a greater (P less than 0.05) proportion were classified as being in metaphase I or II of meiosis after hCG treatment (86%) compared to no ovulatory stimulus (13%), GnRH-1 (0%), GnRH-3 (43%), and GnRHa (12%). Thus, GnRH elicits a transient LH surge that can be extended by GnRH-3 or GnRHa in stimulated cycles of monkeys.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Titrating luteinizing hormone surge requirements for ovulatory changes in primate follicles. II. Progesterone receptor expression in luteinizing granulosa cells.

The events in granulosa cells that are initiated by the midcycle LH surge during luteinization of the primate follicle are poorly defined. This study was designed 1) to determine whether an ovulatory dose of hCG can induce progesterone receptors (PR) in macaque granulosa cells, and if so, 2) to begin titrating gonadotropin requirements for PR expression and progesterone production by luteinizing granulosa cells. Rhesus monkeys were treated with human FSH and LH for up to 9 days to stimulate the growth of multiple follicles. The next day, animals (n = 4-5/group) received: 1) no ovulatory stimulus; 2) 1000 IU hCG, im; 3) one injection of 100 micrograms GnRH, sc (GnRH-1); 4) three injections of GnRH (GnRH-3) at 3-h intervals (0800, 1100, and 1400 h); or 5) two injections of 50 micrograms GnRH agonist (GnRHa), sc, 8 h apart (0800 and 1700 h). Granulosa cells obtained by follicle aspiration 27 h after the hCG or initial GnRH/GnRHa injection or on days 8 or 10 from animals receiving no ovulatory stimulus were processed for indirect immunocytochemistry using a monoclonal antibody to human PR (JZB39). Specific staining for PR, determined by comparing cells incubated with PR antibody vs. a nonspecific antibody, was undetectable in granulosa cells from monkeys without an ovulatory stimulus. In contrast, the majority (64 +/- 5%) of cells from hCG-treated animals stained intensely for PR. In the GnRH/GnRHa groups, granulosa cells from only one animal (i.e. one GnRH-3 monkey) showed positive staining for PR. During 24-h culture in Ham's F-10 medium containing 10% monkey serum, basal progesterone production by cells from the hCG-treated group (2163 nmol/L.8 x 10(4) cells) was higher than that by cells from the no ovulatory stimulus/GnRH-1/GnRH-3/GnRHa groups (60, 111, 194, and 332 nmol/L, respectively). However, granulosa cells from the hCG-treated group were less responsive to hCG in vitro in terms of enhanced progesterone production (2 times control levels) than cells from the other four groups (up to 30 times control levels). This study provides direct evidence that an ovulatory dose of hCG induces PR expression in granulosa cells of luteinizing follicles during stimulated cycles in rhesus monkeys. However, repeated injections of GnRH/GnRHa that produced surge levels (greater than 100 ng/mL) of endogenous LH for up to 14 h failed to induce PR expression or progesterone production by granulosa cells. Thus, an extended LH surge more typical of that in the normal menstrual cycle (48-50 h) may be necessary for PR expression and luteinization of granulosa cells in primate follicles.

Animals↗
PubMed1990

Maturity at collection and the developmental potential of rhesus monkey oocytes.

The purpose of this study was to evaluate the in vitro fertilizability of rhesus monkey oocytes and the developmental capacity of the resulting embryos as they relate to oocyte maturation at the time of follicular aspiration. Animals were hyperstimulated with human follicle-stimulating hormone (hFSH) and human luteinizing hormone (hLH), with follicular aspiration performed 27 h after administration of an ovulatory stimulus (1000 IU human chorionic gonadotropin [hCG] or 3 x 100 micrograms gonadotropin-releasing hormone [GnRH]). In 7 animals exhibiting a continuously rising pattern of serum estradiol through Day 10 of hyperstimulation, 45 germinal vesicle-intact (GV), 106 metaphase I (MI), and 24 metaphase II (MII) oocytes were collected and cultured in vitro. Upon reaching MII, oocytes were inseminated with 5 x 10(4) motile sperm/ml. Twenty-four percent of GV oocytes cultured in vitro matured to MII with 11 inseminated and none fertilized. Seventy-three percent of MI oocytes matured to MII in vitro with 50% inseminated and 32% fertilized. Oocytes collected at MII stage and inseminated underwent fertilization at a high rate of efficiency (93%). Pronuclear to 8-cell stage embryos were frozen and, upon thawing, 67% (10/15) survived with all blastomeres intact. Frozen-thawed embryos (2- to 6-cell) were transferred to the oviducts of 4 recipients (2 embryos/recipient) during the early luteal phase (1-3 days post LH surge) of natural menstrual cycles. Three twin pregnancies resulted. Thus, a positive correlation exists between the degree of nuclear maturation of rhesus monkey oocytes at collection and their potential for fertilization in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Intraluteal infusions of prostaglandins of the E, D, I, and A series prevent PGF2 alpha-induced, but not spontaneous, luteal regression in rhesus monkeys.

A luteotropic role for prostaglandins (PGs) during the luteal phase of the menstrual cycle of rhesus monkeys was suggested by the observation that intraluteal infusion of a PG synthesis inhibitor caused premature luteolysis. This study was designed to identify PGs that promote luteal function in primates. First, the effects of various PGs on progesterone (P) production by macaque luteal cells were examined in vitro. Collagenase-dispersed luteal cells from midluteal phase of the menstrual cycle (Day 6-7 after the estimated surge of LH, n = 3) were incubated with 0-5,000 ng/ml PGE2, PGD, 6 beta PGI1 (a stable analogue of PGI2), PGA2, or PGF2 alpha alone or with hCG (100 ng/ml). PGE2, PGD2, and 6 beta PGI1 alone stimulated (p less than 0.05) P production to a similar extent (2- to 3-fold over basal) as hCG alone, whereas PGA2 and PGF2 alpha alone had no effect on P production. Stimulation (p less than 0.05) of P synthesis by PGE2, PGD2, and 6 beta PGI1 in combination with hCG was similar to that of hCG alone. Whereas PGA2 inhibited gonadotropin-induced P production (p less than 0.05), that in the presence of PGF2 alpha plus hCG tended (p = 0.05) to remain elevated. Second, the effects of various PGs on P production during chronic infusion into the CL were studied in vivo. Saline with or without 0.1% BSA (n = 12), PGE2 (300 ng/h; n = 4), PGD2 (300 ng/h; n = 4), 6 beta PGI1 (500 ng/h; n = 3), PGA2 (300 ng/h; n = 4), or PGF2 alpha (10 ng/h; n = 8) was infused via osmotic minipump beginning at midluteal phase (Days 5-8 after the estimated LH surge) until menses. In addition, the same dose of PGE, PGD, PGI, or PGA was infused in combination with PGF2 alpha (n = 3-4/group) for 7 days. P levels over 5 days preceding treatment were not different among groups. In 5 of 8 monkeys receiving PGF2 alpha alone, P declined to less than 0.5 ng/ml within 72 h after initiation of infusion and was lower (p less than 0.05) than controls. The length of the luteal phase in PGF2 alpha-infused monkeys was shortened (12.3 +/- 0.9 days; mean +/- SEM, n = 8; p less than 0.05) compared to controls (15.8 +/- 0.5). Intraluteal infusion of PGE, PGD, PGI, or PGA alone did not affect patterns of circulating P or luteal phase length.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Disparate effects of the prostaglandin synthesis inhibitors, meclofenamate, and flurbiprofen on monkey luteal tissue in vitro.

Intraluteal infusion of the prostaglandin (PG) synthesis inhibitor, sodium meclofenamate (Mec) causes premature luteolysis in rhesus monkeys. To evaluate further the actions of PG synthesis inhibitors in primate luteal function, we examined the in vitro effects of Mec and another inhibitor, flurbiprofen (Flur), on PG, cAMP, and progesterone (P) production by macaque luteal tissue obtained at midluteal phase of the menstrual cycle. First, collagenase dispersed luteal cells were incubated with 0-100 microM Mec or Flur, either alone or in the presence of 10 microM arachidonic acid (AA) to assess PGF2 alpha and PGE2 synthesis. Levels of both PGF2 alpha and PGE2 were stimulated (P less than 0.05) by AA (3.3- and 5.8-fold, respectively). Maximal suppression (P less than 0.01) of basal and AA-stimulated PGF2 alpha and PGE2 synthesis was elicited by 1 microM Mec and Flur. Second, adenylate cyclase activity, measured by the conversion of alpha 32P-ATP to alpha 32P-cAMP, was monitored in luteal homogenates exposed to increasing doses of Mec and Flur either alone or with maximal stimulatory doses of hCG, PGE2, or PGI2. Mec elicited a dose-dependent reduction (P less than 0.01) in control activity (incubated with 50 microM GTP), as well as inhibiting hCG- and PG-stimulated activity. The presence of 100 microM Mec suppressed (P less than 0.01) hCG-, PGE2- and PGI2-stimulated activity to control levels, but had no effect on activity stimulated by GMP-P(NH)P or forskolin. In contrast, Flur at any dose did not alter control activity or that stimulated by hormonal or nonhormonal activators. Third, P production by dispersed luteal cells was quantified during exposure to 0, 1, and 100 microM Mec or Flur alone or with maximal stimulatory doses of hCG, PGE2, PGD2, 6 beta PGI1, PGA2, or dibutyryl cAMP (dbcAMP). All hormones and dbcAMP stimulated (P less than 0.01) P synthesis 2-3 fold over basal levels, except PGA2, which had no effect. The presence of 100 microM Mec reduced (P less than 0.01) basal P production by 62% and abolished (P less than 0.05) hCG-, PG-, and dbcAMP-induced stimulation. Conversely, neither 1 microM Mec nor either dose of Flur affected P synthesis in the absence or presence of hormones or dbcAMP. These data indicate that: 1) Mec and Flur are potent inhibitors of PG synthesis in primate luteal cells in vitro and 2) higher doses of Mec suppress PG- and gonadotropin-sensitive adenylate cyclase activity and P production.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1990

The effect of intraluteal infusion of deglycosylated human chorionic gonadotropin on the corpus luteum in rhesus monkeys.

Removal of the carbohydrates from hCG results in an antagonist (degly-hCG) that competitively inhibits hCG/LH-stimulated adenylate cyclase in macaque luteal tissue in vitro, but its effect in vivo is controversial. To examine the effect of degly-hCG on the lifespan and steroidogenic activity of the primate corpus luteum, the antagonist was administered to female rhesus monkeys (n = 7) beginning at the midluteal phase of the menstrual cycle. In a control cycle the saline vehicle was infused via an osmotic minipump directly into the corpus luteum. In a subsequent cycle, one of three dose rates of degly-hCG (0.001, 0.009, and 0.09 nmol/h) was infused into the corpus luteum. Pump implantation and infusion began 5-9 days after the midcycle LH surge and continued for 7 days. Peripheral venous blood was collected daily from day 8 of the cycle until menses, and serum progesterone levels were determined by RIA. Progesterone levels and patterns were similar in animals that received either the saline vehicle or degly-hCG, and the length of the luteal phase in monkeys receiving any dose of degly-hCG (16.4 +/- 0.5 days) was not different from that in animals receiving a control infusion (16.1 +/- 0.9 days). In a corollary study, an intraluteal infusion of degly-hCG (0.009 nmol/h) in the midluteal phase did not prevent stimulation of progesterone levels after im injection of hCG (15 IU/day for 5 days). We conclude that whereas degly-hCG is a useful tool to examine gonadotropin action in vitro, it is not a potent gonadotropin antagonist in vivo.

Adenylyl Cyclases↗
PubMed1990

Are human luteinizing granulosa cells a site of action for progesterone and relaxin?

Specific nuclear staining for progesterone receptor (PR) was detected by immunocytochemistry in human granulosa cells (GCs) obtained from in vitro fertilization protocols. The percent of PR-positive cells (60% to 80%) remained unchanged during 7 days of culture in media containing fetal calf serum, in the absence or presence of human chorionic gonadotropin (hCG) or the progesterone antagonist RU486. Progesterone (P) production by GCs cultured on extracellular matrix from bovine corneal endothelial cells was stimulated by hCG and prostaglandin E2 (PGE2). However, addition of RU486 or human relaxin had no effect on control, hCG-, or PGE2-stimulated P production. Thus, the receptor data are consistent with an autocrine action of P in luteinizing GCs, but initial experiments in cell culture did not define a role for P or relaxin in modulating luteal steroidogenesis.

Cells, Cultured↗
PubMed1989

Comparison of different regimens of human gonadotropins for superovulation of rhesus monkeys: ovulatory response and subsequent luteal function.

This study was designed to identify suitable treatment regimens of human gonadotropin for superovulation of rhesus monkeys. At menses, female monkeys were given one of three regimens: Plan A [days 1 to 6, 60 IU human follicle-stimulating hormone (hFSH); days 7 to 9, 60 IU hFSH/60 IU human luteinizing hormone (hLH)], Plan B [days 1 to 3, 75 IU FSH/20 IU LH; days 4 to 6, 60 IU FSH/20 IU LH; days 7 to 9, 45 IU FSH/45 IU LH], or Plan C [days 1 to 9, 60 IU FSH/60 IU LH]. On day 10, human chorionic gonadotropin (hCG; 1000 IU) was administered. Serum estrogen levels peaked on the day of hCG treatment (day 10) in Plans A and C but earlier (day 8) in Plan B. An oviduct lavage recovered 1 to 3 oocytes in Plan B but 3 to 13 oocytes in the other treatment groups. Peak progesterone levels in the luteal phase were greater (P less than 0.05) in animals receiving Plan A or C than Plan B. Regardless of treatment group, progesterone levels declined abruptly 7 days after ovulation induction; the length of the luteal phase in all groups was significantly less than that of normal menstrual cycles. We conclude that regimens of hFSH and hLH (i.e., Plans A and C), followed by hCG, reliably superovulate rhesus monkeys. However, the premature decline in luteal function around the typical time of implantation may compromise pregnancy initiation and maintenance.

Animals↗
PubMed1989

Isolation and characterization of cell subpopulations from the monkey corpus luteum of the menstrual cycle.

This study was designed to test the hypothesis that the corpus luteum of primate species consists of cell subpopulations that differ in physical characteristics, function, and regulation by endocrine and paracrine factors. The corpus luteum (n = 25) was removed from rhesus monkeys at the mid-luteal phase of the menstrual cycle (Days 7-8 after the surge of luteinizing hormone, LH) and enzymatically dispersed. Freshly dispersed cells were analyzed and sorted on the basis of their forward and 90 degrees light scatter (FLS and 90LS, respectively) properties using an EPICS C flow cytometer. Freshly dispersed and sorted cells were fixed, stained histochemically for the presence of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), and measured to determine their diameters. Freshly dispersed (MIX) and sorted cells from corpora lutea during the early (Days 4-5 after the LH surge; n = 4) and mid-luteal phases of the cycle were incubated in vitro and steroid production was assessed. The size distribution of dispersed cells revealed four peaks that corresponded to small (10-15 microns in diameter) 3 beta-HSD-negative, and small, medium (16-20 microns), and large (greater than 20 microns) 3 beta-HSD-positive cells. Analysis of dispersed cells for FLS and 90LS demonstrated two continua (C alpha and C beta). C alpha contained single cells and cell clusters; 99.7 +/- 0.3% (n = 3) of the cells were less than or equal to 15 microns in diameter and 96.7 +/- 0.3% were 3 beta-HSD-negative. C alpha cells produced low levels of progesterone (0.2 +/- 0.1 ng/ml per 5 x 10(4) cells; n = 3) in vitro under basal conditions. C beta consisted of single cells from 10 microns to 40 microns in diameter and contained the lipid-filled and 3 beta-HSD-positive cells. Two regions (R1 and R3) of C beta were defined and their cells separated. In R1, 96 +/- 2% (n = 3) of the cells had diameters of less than or equal to 15 microns, whereas 82 +/- 4% (n = 3) of those in R3 were greater than or equal to 20 microns. Basal progesterone production by R3 cells from early luteal phase of the cycle was 12 times greater than that by R1 cells (n = 3 per group).(ABSTRACT TRUNCATED AT 400 WORDS)

3-Hydroxysteroid Dehydrogenases↗
PubMed1989

In vitro fertilization and embryo transfer in the rhesus monkey.

Twenty-three rhesus monkeys were subjected to 9 days of ovarian hyperstimulation with sequential exposure to human follicle-stimulating hormone (hFSH) and then human luteinizing hormone (hLH) + hFSH. Six animals (26%) did not exhibit sustained, elevated levels of circulating estradiol, primarily due to the occurrence of a premature surge of endogenous LH (n = 4). Seventeen animals (74%) responded with supraphysiologic levels of circulating estradiol (peak value: means = 4480 pg/ml) and received human chorionic gonadotropin (hCG) on Day 10. Oocytes were collected 26 h later by aspiration of large antral follicles. Oocyte quantity (means = 18/animal) and quality (63% mature) were evaluated by in vitro fertilization (IVF), embryonic development, and embryo transfer to foster mothers. Modified conditions for the successful fertilization of oocytes used a Tyrode's augmented (TALP) medium supplemented with 0.3% bovine serum albumin (BSA). Oocytes were inseminated at the metaphase II stage with ejaculated, washed sperm (50 100 x 10(3)/ml) preexposed at ambient temperature to caffeine and dibutyryl cyclic adenosine 3'5'-monophosphate. Successful fertilization ranged from 26% to 75%. In one experiment, 5 of 11 embryos produced by IVF developed in vitro to hatched blastocysts. Embryo freezing employed a propanediol-based protocol and was applied to early cleavage-stage embryos with 100% (5 of 5) post-thaw survival. Two frozen-thawed embryos were transferred transtubally on 3 occasions into rhesus monkeys during the early luteal phase of spontaneous menstrual cycles. One pregnancy resulted, which proceeded normally to the unassisted delivery of a male offspring 170 days after the LH surge. We conclude that this sequential regimen of human gonadotropins provides a cohort of oocytes from rhesus monkeys that will complete meiotic maturation and fertilize in vitro, with embryonic development proceeding in vitro and in vivo. The production of putative antibodies to human gonadotropins, assessed by the presence of Protein A-precipitated hCG binding components in sera, limits the repeated use of monkeys in the hyperstimulation protocol. Nevertheless, this model system should facilitate further studies on oocyte maturation, fertilization, and early embryogenesis in primates.

Animals↗
PubMed1989

The function and regulation of the primate corpus luteum during the fertile menstrual cycle.

Figure 2 summarizes the changes in endocrine function and the factors which regulate the primate corpus luteum during the fertile menstrual cycle. The classical luteotropic role of LH during the menstrual cycle is superceded by CG at or before the time of implantation. The role of local factors in modulating luteal function is an area of continued research, as some factors are deemed less important (i.e., estrogen, at least prior to luteal rescue) and other possibilities (progesterone, prostaglandins, and relaxin) arise. The role of local factors has not yet been studied in the corpus luteum following its rescue in early pregnancy. Finally, it is apparent that a different type of "shift" precedes the recognized luteal-placental shift in early pregnancy, when the corpus luteum enhances or begins new activities as progesterone secretion declines. These new or augmented activities occur despite apparent desensitization of CG-responsive cAMP-mediated pathways in luteal cells. Although the cellular events promoting these changes are not known, it seems reasonable to propose that the resulting products, including estrogen (as discussed in Dr. Moudgal's chapter) and relaxin are important in early pregnancy. Thus the term "luteal-placental shift" may be a misnomer, as other activities which promote gestation continue within the corpus luteum for a limited time.

Animals↗
PubMed1988

125I-luteinizing hormone (LH) binding to soluble receptors from the primate (Macaca mulatta) corpus luteum: effects of ethanol exposure.

In vitro exposure to alcohols unmasks additional binding sites for gonadotropin in cell/membrane preparations of the corpus luteum of rhesus monkeys. In the current study, we compared the effects of ethanol on gonadotropin receptors solubilized from macaque luteal membranes to those on receptors associated with the lipid bilayer. Treatment with 1% Triton X-100 for 30 min at 4C, followed by precipitation with polyethylene glycol, resulted in recovery of 50% more binding sites for 125I-human luteinizing hormone (hLH) than were available in particulate preparations (p less than 0.05). However, the soluble receptors displayed a 3-fold lower affinity for 125I-hLH (p less than 0.05). Conditions which enhanced LH binding to particulates, i.e., 1-8% ethanol at 25C, decreased specific 125I-hLH binding to soluble receptors. Steady-state LH binding to soluble receptors during incubation at 4C was half of that observed at 25C. The presence of 8% ethanol at 4C restored LH binding to levels observed in the absence of ethanol at 25C. Thus, LH binding sites in the primate corpus luteum can be effectively solubilized with Triton X-100. The different binding characteristics of particulate and soluble receptors, including the response to ethanol exposure, suggest that the lipid environment in the luteal membrane modulates the availability and affinity of gonadotropin receptors.

Animals↗
PubMed1988

Luteal function following ovarian stimulation in rhesus monkeys for in vitro fertilization: atypical response to human chorionic gonadotropin treatment simulating early pregnancy.

This study determined if corpora lutea of hyperstimulated cycles in rhesus monkeys could be "rescued" by the pregnancy signal, chorionic gonadotropin (CG), given at the typical time of implantation. At menses, female monkeys received human follicle-stimulating hormone (hFSH, 60 IU, days 1 to 6) followed by human menopausal gonadotropin (hMG, 60 IU hFSH/60 IU luteinizing hormone [hLH], days 7 to 9). On day 10, human chorionic gonadotropin (hCG) was given to mimic the LH surge. Nine days later, a regimen of daily increasing doses of hCG (15 to 360 IU twice a day) was initiated to simulate rescue of the corpus luteum in early pregnancy. Serum levels of progesterone (P) increased through day 5 of the luteal phase but then declined. Circulating levels of bioactive LH were significantly less on days 7 to 9 of the luteal phase than at this stage in the natural cycle. The hCG regimen extended (P less than 0.05) the luteal phase in five of six animals. The hCG treatment elicited a persistent increase (P less than 0.05) in circulating P levels, rather than a transient rise typical of normal or simulated pregnancy in natural cycles. The authors conclude that (1) corpora lutea of hyperstimulated cycles can respond to CG, but (2) there are differences in luteal function during both the luteal phase and simulated early pregnancy that may be due to inadequate luteal development or the abnormal gonadotropin milieu existing after ovulation or both.

Animals↗
PubMed1988

Adenylate cyclase in the primate corpus luteum during chorionic gonadotropin treatment simulating early pregnancy: homologous versus heterologous desensitization.

Stimulation of the primate corpus luteum by endogenous CG in early pregnancy or by exogenous CG in simulated conditions is transient despite continued exposure to this luteotropic hormone. The transitory response to CG is not due to the down-regulation of gonadotropin receptors. The current studies were designed to determine if the transient response involves a postreceptor lesion at the membrane level, i.e. the loss of CG receptor activation of adenylate cyclase. Nonpregnant female rhesus monkeys received increasing doses of hCG for up to 10 days beginning near the typical time of implantation (9 days post-LH surge) to simulate early pregnancy. Corpora lutea were removed at specific intervals after the onset of hCG treatment, luteal homogenates were prepared, and adenylate cyclase activity was assessed by the conversion of [alpha-32P]ATP to [32P] cAMP. Basal activity of adenylate cyclase was unchanged throughout the in vivo hCG treatment interval. Nonhormonal activators, such as forskolin (100 microM) and 5'-guanylylimidodiphosphate (50 microM) stimulated (P less than 0.05) adenylate cyclase to a similar extent (greater than 10-fold the control level) throughout hCG treatment. On day 0, both gonadotropins (hCG and human LH; 250 nM) and prostaglandins (PGE2 and PGI2; 500 nM) stimulated cAMP production (approximately 3-fold the control level; P less than 0.05). The responses of adenylate cyclase to PGE2 and PGI2 did not diminish throughout the in vivo hCG treatment. In contrast, exposure to hCG for 3 days reduced the sensitivity of adenylate cyclase to gonadotropin. Moreover, adenylate cyclase in luteal tissue after 6-10 days of treatment was insensitive to hCG. The loss of gonadotropin sensitivity of adenylate cyclase by 6 days of hCG treatment correlated with the decline in circulating progesterone levels. These results demonstrate that 1) the gonadotropin-responsive adenylate cyclase of the macaque corpus luteum is also stimulated by paracrine factors, notably PGs of the E and I series; and 2) CG exposure stimulating early pregnancy conditions leads to homologous, not heterologous, desensitization of the adenylate cyclase system. We hypothesize that homologous desensitization of the adenylate cyclase system is an important mechanism leading to the transient response of the primate corpus luteum to CG in early pregnancy.

Adenylyl Cyclases↗