Biomedical subjects

D R Danforth

Publications and source records attributed to D R Danforth.

At least 37 records · Page 2Linked to original sources

PubMed1991

Early folliculogenesis in primate ovaries: testing the role of estrogen.

The purpose of this study was to examine the effect of an exogenous estrogen, diethylstilbestrol (DES), on follicle development in the ovary of a juvenile primate. The immature cynomolgus monkey (12-22 mo) was used as a model since ovaries at this age lack endogenous gonadotropin support but are capable of responding to exogenous hormonal stimulation. In addition, the pituitary gland receives virtually no GnRH stimulation and under these conditions lacks responsiveness to estrogen feedback. Two groups of three monkeys each received DES for 14 days. Members of the second group also were given GnRH antagonist to assure no GnRH action upon the gonadotropes. The left ovary of each monkey was removed just prior to Day 1 of DES treatment and served as the control. The right ovary was removed on Day 14 of treatment. Both ovaries from each monkey were prepared for evaluation by light microscopy. Results indicated that both the number of preantral follicles and the mean number of medium-sized (0.5-1 mm in diameter) developing antral follicles decreased significantly (p less than 0.05) in the DES-treated ovaries with no increase in early-atretic antral follicles. These data suggest that DES, at the amount administered, inhibits the growth of both preantral and medium-sized antral follicles in the primate. Whether these effects are manifest directly at the follicle level or are mediated by other mechanisms remains to be determined.

Animals↗

PubMed1991

Inhibition of pituitary gonadotropin secretion by the gonadotropin-releasing hormone antagonist antide. I. In vitro studies on mechanism of action.

The GnRH antagonist antide is among the most promising "third generation" compounds available for clinical evaluation. In primates, antide manifests prolonged (several weeks) and reversible inhibition of pituitary gonadotropin secretion after a single high dose injection. In the present study, we have examined the effects of antide on pituitary gonadotropin secretion in vitro. Dispersed anterior pituitary cells from adult female rats were plated (48 h; 5 x 10(5) cells/well), washed, and exposed to increasing concentrations of antide for up to 48 h. Media were removed, and cells were washed twice and then incubated with GnRH (1 x 10(-8) M) plus antide for 4 h. Media and cell lysates were assayed for LH/FSH by RIA. Antide had no effect on basal LH/FSH secretion at any dose tested (10(-6)-10(-12) M). In contrast, GnRH-stimulated LH/FSH secretion was inhibited by this GnRH antagonist in a dose- and time-dependent manner. When incubated simultaneously, antide blocked GnRH-stimulated gonadotropin secretion, with a maximal effect at 10(-6) M (ED50, 10(-7) M). Preincubation of pituitary cells with antide for 6-48 h before GnRH exposure shifted the dose-response curve to the left; the maximally effective dose was 10(-8) M; the ED50 was 10(-10) M antide after 48-h preincubation. Intracellular LH/FSH levels increased concomitant with the decrease in secreted gonadotropins. Total LH/FSH levels (secreted plus cell content) remained unchanged. The inhibition of LH secretion by antide was specific for GnRH-stimulated gonadotropin secretion; antide had no effect on K(+)-stimulated LH secretion. Moreover, antide had little or no residual effect on LH secretion; full recovery of GnRH responsiveness in vitro occurred within 4 h after removal of antide. Lineweaver-Burke analysis of antide inhibition of GnRH-stimulated LH secretion indicated that antide is a direct competitor of GnRH at the level of the pituitary GnRH receptor. In summary, antide is a pure antagonist of GnRH stimulation of gonadotropin secretion; no agonistic actions of antide were manifest in vitro. Moreover, antide has no apparent noxious or toxic effect on pituitary cells in culture; the actions of antide are immediately reversible upon removal of antide from pituitary gonadotropes. We conclude that the long term inhibition of gonadotropin secretion by antide in vivo is not due to deleterious effects of this compound at the level of the pituitary gonadotrope.

Animals↗

PubMed1991

Inhibition of pituitary gonadotropin secretion by the gonadotropin-releasing hormone antagonist antide. II. Development of an in vitro bioassay for characterization of pharmacokinetics and pharmacodynamics of antide in circulation.

Previous data from this laboratory revealed a rapid and unexpectedly long inhibition of pituitary gonadotropin secretion in ovariectomized monkeys after a single high dose injection of the GnRH antagonist antide. This extended action of antide may correlate with an extended presence of antide in the peripheral circulation. We have reported on use of a RRA for antide in serum; however, during such a prolonged presence in the body, the possibility of catabolic loss of biological activity remained to be analyzed. In the present study, we have developed an in vitro pituitary cell bioassay for antide to investigate the pharmacokinetics and possible mechanism(s) contributory to its long action. Dispersed anterior pituitary cells from adult female rats were plated (48 h; 5 x 10(5) cells/well), washed, and incubated with 0.024-6 ng antide for 24 h. Media were removed, and cells were washed twice and then incubated with GnRH (1 x 10(-8) M) plus antide standards or serum samples for 4 h. Before antide injection into long term ovariectomized monkeys, peripheral GnRH antagonist levels were undetectable. One day after a single injection (3.0 mg/kg, sc, in 50% propylene glycol-water), the level of antide was 31 +/- 13 ng/ml (n = 3). Thereafter, antide levels declined slowly and were still detectable (greater than 1.4 ng/ml) in two of three monkeys 31 days after injection. After iv administration (3.0 mg/kg; n = 2), peripheral antide levels followed a similar pharmacokinetic profile and declined slowly. Detectable antide concentrations were still present 36 days after single iv injection in both monkeys. The circulating half-lives of antide were 1.7 and 14.5 days for the first and second phases, respectively. Peripheral LH levels were suppressed to the limits of detectability within 1 day and slowly recovered to pretreatment levels within 30 +/- 5 days after sc or iv antide treatment. The ratio of bioactive antide to antide levels measured by RRA was similar throughout the study (chi = 1.24 +/- 0.09; range, 0.40-2.22), although there was a trend toward an increased B/R ratio at the end of the study. In summary, we have developed an in vitro bioassay using cultured rat pituitary cells to measure biologically active antide concentrations in peripheral circulation after sc and iv treatments. The prolonged action of antide on pituitary gonadotropin secretion in vivo is apparently due to the continued presence of biologically active antide in circulation after a single injection.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1991

Suppression of ovarian estradiol secretion by a single injection of antide in cynomolgus monkeys during the early follicular phase: immediate, sustained, and reversible actions.

We examined the effects of the GnRH antagonist antide on ovarian estrogen secretion after a single administration in intact cycling cynomolgus monkeys (n = 5/group) during the early follicular phase. Antide treatment on menstrual cycle day 2 resulted in a dose-dependent increase in menstrual cycle lengths (mean +/- SEM) to 38 +/- 3, 49 +/- 8, and 96 +/- 15 days for 3.0, 10.0, and 30.0 mg/kg antide, respectively, in association with inhibition of folliculogenesis and suppression of estradiol concentrations to therapeutic levels. Subsequent resumption of apparently normal ovulatory menstrual cycles occurred in all 15 individuals. In addition, all four monkeys from the group treated with 30 mg/kg antide that were available for subsequent matings became pregnant and had normal babies. Thus, no irreversible consequences or adverse effects of antide on reproductive function in these primates was observed. No allergic or other adverse reactions were found locally or systemically in these primates, even at the highest dose of antide. To the extent that this primate model is a paradigm for clinical therapeutics, a single treatment of antide (30 mg/kg) provides sustained inhibition of ovarian estradiol secretion for about 2 months, thus demonstrating the feasibility of using antide for clinical management of steroid-dependent conditions.

Animals↗

PubMed1990

Progesterone and 17 alpha-hydroxyprogesterone. Novel stimulators of calcium influx in human sperm.

Progesterone and 17 alpha-hydroxyprogesterone (but not other steroids such as testosterone, corticosterone, beta-estradiol, estrone, dehydroepiandrosterone, 20 alpha-hydroxypregnen-3-one, androstenedione, and pregnenolone) were shown to cause an immediate increase, in free cytosolic calcium ([Ca2+]i) in both capacitated and noncapacitated human sperm, using the fluorescent indicator fura 2. Significant increases in [Ca2+]i were observed with 10 ng/ml progesterone, while maximum effects were seen with 1 microgram/ml progesterone. Two other steroids 11 beta-hydroxyprogesterone and 5 alpha-pregnane-3,20-dione exhibited significant activity to increase [Ca2+]i. This increase in [Ca2+]i elicited by progesterone was entirely due to Ca2+ influx from the extracellular medium since the increase in [Ca2+]i was blocked by the Ca2+ chelator EGTA (2.5 mM) and the Ca2+ channel antagonist La3+ (0.25 mM) when added to the medium containing 2.5 mM Ca2+. Progesterone also stimulated the uptake of Mn2+ into sperm as measured by the quenching of fura 2 fluorescence. Progesterone has been found in human follicular fluid at levels capable of stimulating increases in [Ca2+]i. The similarities in responses induced by human follicular fluid and progesterone an increase in [Ca2+]i, and hence the acrosome reaction, is progesterone and/or 17 alpha-hydroxyprogesterone. Progesterone (1 microgram/ml) did not increase [Ca2+]i in somatic cells such as adipocytes, hepatocytes, Balb/c 3T3 cells, normal rat kidney, or DDT1 MF-2 cells. The effects of these progestins to increase [Ca2+]i, by activating a receptor-operated calcium channel, is the first report of such an activity in sperm. This phenomena possibly opens up a new field of steroid action in the area of sterility, fertility, and contraception at the level of the sperm.

17-alpha-Hydroxyprogesterone↗

PubMed1990

Single dose long-term suppression of testosterone secretion by a gonadotropin-releasing hormone antagonist (Antide) in male monkeys.

This study was designed to find the minimal single dose of Antide (Nal-Lys GnRH antagonist) that would provide long-term inhibition of serum testosterone levels in adult male monkeys. At 3 mg/kg (sc), Antide blocked testosterone secretion for only a few days. However, when the dose of Antide was raised to 10 mg/kg, some of the males manifested testosterone inhibition lasting more than 60 days, while shorter durations of action were found in others. These preliminary findings increase our interest in studying Antide as a potential male contraceptive agent, when combined with androgen replacement therapy, as well as for therapeutic applications in men having prostatic carcinoma. Importantly, Antide lacks the sometimes deleterious "flare" effect known to occur when GnRH agonists are used to treat these patients.

Animals↗

PubMed1990

Intermittent GnRH antagonist plus progestin contraception conserving tonic ovarian estrogen secretion and reducing progestin exposure.

The present study was designed to evaluate the effectiveness of a once-weekly regimen of GnRH antagonist followed by a progestin as a potential new contraceptive method. On menstrual cycle days 2, 9, 16, and 23 (onset of menses = Day 1) monkeys were divided into two groups: 1) those injected sc with 0.1 mg/kg Nal-Glu GnRH antagonist in saline and those given only vehicle (control). On cycle days 15 to 26, each treated female was administered 25 micrograms norgestimate/day orally. This was continued for three treatment cycles (84 days). Weekly injections of Nal-Glu GnRH antagonist effectively blocked completion of folliculogenesis, ovulation, and corpus luteum function as judged by serum LH, E2, and P levels. Serum progesterone was undetectable (less than 0.1 ng/ml) during the treatment cycles. Importantly, serum estradiol levels during GnRH antagonist plus norgestimate treatments were maintained at 35 +/- 7 pg/ml. Upon the cessation of norgestimate treatment on day 26 in each cycle, menses uniformly began within 2 or 3 days. Regarding recovery, apparently normal and presumably ovulatory menstrual cycles, as judged by timely estradiol elevations, midcycle LH surges, and luteal phase progesterone patterns, were manifest immediately following termination of the final GnRH antagonist plus norgestimate treatment cycle. Endometrial biopsies removed on day 26 of control cycles, and on day 26 of the third treatment cycle revealed appropriate late secretory phase endometrium having tortuous endometrial glands and superficial stromal edema. Histological sections of ovaries removed at the end of the GnRH antagonist plus norgestimate treatment revealed multiple small and medium-sized developing and atretic follicles, having maintained serial ablation of the potentially maturing follicles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

In vivo and in vitro modulation of gonadotropin-releasing hormone metabolism by estradiol and progesterone.

The metabolism of GnRH by membrane-bound and serum-degrading enzymes may play an important role in the regulation of pituitary gonadotropin secretion. We examined GnRH metabolism by pituitary cells in vitro and the metabolism of exogenously administered GnRH in vivo in the presence and absence of estradiol (E2) and progesterone (P4). Ovariectomized cynomolgus monkeys were implanted with E2- and/or P4-filled Silastic capsules to simulate the estrogen and progesterone patterns of the normal menstrual cycle. Peripheral levels of GnRH after a 1-microgram iv injection were highest in the E2-replaced monkeys. Peripheral GnRH levels reached a higher peak and remained in circulation longer in monkeys treated with E2-filled Silastic implants than in those treated with E2 plus P4 or nonsteroid-replaced ovariectomized monkeys. In agreement with the in vivo data, GnRH was rapidly metabolized by acutely dispersed cells isolated from pituitaries removed from nonsteroid-replaced ovariectomized monkeys. Priming with E2 followed by P4 in vivo attenuated the clearance of GnRH in vitro, and E2 treatment alone almost completely blocked the ability of pituitary cells to bind and/or degrade GnRH in vitro. In a parallel study, cells prepared from rat pituitaries removed on the morning of proestrus (when serum E2 is highest) metabolized GnRH in vitro more slowly than pituitary cells removed at estrus, diestrus, or metestrus. In summary, our data suggest that E2 inhibits GnRH metabolism by monkey and rat pituitary cells in vitro and exogenously administered GnRH in vivo. Although the precise mechanism of action of E2 is unknown, inhibition of membrane-bound and serum proteases seems likely. The action of E2 may be to increase GnRH presentation to the pituitary and enhance LH and FSH secretion under conditions where circulating levels of the hormone are elevated, such as at midcycle.

Animals↗

PubMed1990

Extended presence of antide (Nal-Lys GnRH antagonist) in circulation: prolonged duration of gonadotropin inhibition may derive from antide binding to serum proteins.

Previous data from this laboratory revealed a rapid (-12h) and unexpectedly long (-30 days) inhibition of pituitary gonadotropin secretion after a single injection of Antide (Nal-Lys GnRH antagonist) in ovariectomized (OVX) monkeys. Although the apparent mechanism of action of Antide is competitive occupancy of GnRH receptors, the etiology of the prolonged action is unknown. Here, we report development of a radioreceptor assay to measure circulating Antide levels to determine the mechanism(s) of its long duration of action. Five long-term OVX monkeys were injected with Antide (3.0 mg/kg). Blood samples were collected daily for 30 days, and thereafter on alternate days until day 60. Following sc or iv Antide injection, peripheral luteinizing hormone (LH) levels declined from 281 +/- 19 ng/ml to 29 +/- 3 ng/ml within one day (P less than 0.05). LH levels slowly recovered to pretreatment levels within 35 +/- 7 days. Peripheral Antide levels were 16,531 +/- 4,432 ng/ml within 15 minutes following iv injection, and 52 +/- 21 ng/ml at 1 day after sc Antide injection. Interestingly, thereafter clearance of Antide-from the peripheral circulation was very slow, with an apparent t1/2 (second phase) of 6.5 days following iv administration. Detectable Antide levels were present in the peripheral circulation for more than one month in all five monkeys. In a second experiment, incubation of 125I-Tyro Antide with OVX monkey serum resulted in binding of the labelled peptide to serum proteins and reduction of 125I-Tyro Antide binding to pituitary receptors. Following gel permeation chromatography, greater than 70% of the radioactivity was associated with a 66 kDa protein(s). In conclusion, the prolonged duration of gonadotropin inhibition by Antide seems to derive from the long circulatory half-life of this molecule. In turn, this extended action of Antide may be manifest, at least in part, by binding to serum protein(s) that serves as a built-in peripheral depot release mechanism.

Animals↗

PubMed1990

A novel regimen of gonadotropin-releasing hormone (GnRH) antagonist plus pulsatile GnRH: controlled restoration of gonadotropin secretion and ovulation induction.

Using a primate model, we have tested a novel regimen of gonadotropin-releasing hormone (GnRH) antagonist plus pulsatile GnRH for the achievement of controlled restoration of gonadotropin secretion and ovulation induction. As a prelude, ovariectomized cynomolgus monkeys (n = 3) were treated with Antide ([N-Ac-D-Nal(2)1, D-pCl-Phe2, D-Pal(3)3, Lys(Nic)5, D-Lys(Nic)6, Lys(iPr)8, D-Ala10]-GnRH) (3 mg/kg per day) for 6 consecutive days. On the 7th day, pulsatile GnRH therapy was initiated in a 7 day-on: 7 day-off regimen for a total of four exposures. Next, four intact monkeys were given Antide to suppress ovarian function (estradiol less than 10 pg/mL) followed by pulsatile GnRH. In the ovariectomized monkeys, Antide-induced suppression of gonadotropin concentrations was reversed by the pulsatile GnRH so that follicle-stimulating hormone concentrations were completely normalized and luteinizing hormone concentrations were returned to within the lower range (+/- 2 SD) of the pretreatment mean. The abruptness of the onset or loss of gonadotropin secretion was precisely synchronized with the weekly on and off phases of the GnRH pulse regimen. In intact monkeys, ovarian steroid secretions were abruptly subdued and then successfully re-established by pulsatile GnRH in the face of sustained circulating levels of Antide. Thus, we conclude that our primate model of combination therapy, GnRH antagonist plus pulsatile GnRH, establishes the possibility of a new clinical treatment regimen for patients desiring relief from the sequelae of hyperandrogenemia (polycystic ovarian disease) and ovulatory dysfunction.

Animals↗

PubMed1989

Contraceptive potential of RU 486 by ovulation inhibition: I. Pituitary versus ovarian action with blockade of estrogen-induced endometrial proliferation.

In previous studies, RU 486 administration arrested spontaneous folliculogenesis. To investigate the central versus peripheral effects of RU 486 on the ovarian/menstrual cycle, including endometrial proliferation, RU 486 was administered daily (10 mg/kg/day, im) from menstrual cycle day 3 or 7 to day 25 in normal adult cynomolgus monkeys receiving hMG treatment (37.5 IU/day) from days 3-8 (n = 6). RU 486 administration with hMG/hCG therapy did not inhibit ovarian response, as evidenced by steroidogenesis and ovulation. Nine of 23 oocytes retrieved by lavage or follicular aspiration at laparotomy after ovulation induction were morphologically classified as mature preovulatory status. Whereas an endometrial biopsy performed on cycle day 25 in control monkeys revealed an in phase mature secretory endometrium, histologic sections from RU 486 plus hMG/hCG treated females uniformly demonstrated atrophic to weakly proliferative endometrium on cycle day 25, despite serum estradiol levels greater than 300 pg/ml. Three months after the initial 25-day study endometrial biopsies revealed persistent atrophic endometrium, even though repeated ovulation induction with hMG/hCG therapy elevated serum estrogen concentrations. The findings prevailed whether RU 486 treatment began on cycle day 3 or 7. The intermenstrual interval was significantly (P less than 0.01) lengthened by RU 486 treatments (28.5 +/- 2.0, control vs 131.3 +/- 11.5 days, RU 486). In summary, RU 486 consistently blocked ovulation unless hCG was provided and elicited a persistent retardation of early proliferative endometrium when administered daily beginning in early or mid-follicular phase. The normal mitogenic effects of elevated ovarian estrogen secretion on endometrial tissue were quelled, uniformly resulting in amenorrhea. The long-lasting action of RU 486, causing ovulation inhibition and atrophic endometrium, may be due to the depot effect of im injection. In addition, RU 486 did not prevent ovarian steroidogenesis, ovulation or oocyte maturation when an ovulation induction regimen of hMG/hCG was given. These findings show that RU 486 prevented ovulation by diminishing pituitary gonadotropin secretion, rather than by direct effects on ovarian folliculogenesis, and induced amenorrhea by inhibiting estrogen-induced endometrial proliferation.

Animals↗

PubMed1989

Contraceptive potential of RU 486 by ovulation inhibition: II. Suppression of pituitary gonadotropin secretion in vitro.

That the antiprogestin RU 486 delays or inhibits the LH surge, and induces premature luteolysis in monkeys and women concurrent with a reduction in LH/FSH secretion has been reported. Whether this inhibition of gonadotropin release was a result of action at the hypothalamic and/or pituitary level is unknown. Here, we utilized a rat pituitary cell culture system to evaluate direct RU 486 actions on pituitary gonadotropin secretion in vitro. Cell cultures were primed with 10 nM estradiol for 48 h in order to maintain progesterone receptors. Basal and GnRH-induced secretion were evaluated after a 4-hour incubation period. The progesterone antagonist RU 486 inhibited GnRH-induced LH and FSH secretion in a dose-dependent manner, without affecting basal gonadotropin release. This inhibition of gonadotropin secretion was specific and antagonized by addition of progesterone in vitro.

Animals↗

PubMed1989

Contraceptive potential of RU 486 by ovulation inhibition: III. Preliminary observations on once weekly oral administration.

Acute administration of the potent progesterone antagonist RU 486 during the luteal/secretory phase of the menstrual cycle induces premature menses in women and monkeys. Using a variety of regimens, administration of RU 486 during the follicular/proliferative phase causes anovulation and amenorrhea. Single treatment in the late follicular phase blocks the preovulatory LH surge and ovulation; mid-luteal phase administration of RU 486 can cause premature luteolysis. The objective of the present study was to evaluate the contraceptive potential of the antiprogesterone RU 486 during once weekly oral administration in normally cycling cynomolgus monkeys. Oral administration of 25 mg of RU 486 on cycle days 3, 10, 17 and 24 blocked the expected midcycle LH/FSH surges. Interestingly, whereas progesterone remained undetectable throughout the treatment cycle, estradiol levels began to increase during the last two weeks of treatment. In contrast, halving the dose to 12.5 mg did not inhibit apparent ovulation or luteal function, as judged by serum LH, estradiol and progesterone levels. We conclude that at adequate doses, RU 486 effectively blocks ovulation when administered orally in a once weekly regimen. Further studies are warranted to evaluate RU 486 and other progesterone antagonists as potential contraceptive agents.

Animals↗

PubMed1989

"Sunday start" multiphasic oral contraception: ovulation prevention and delayed follicular atresia in primates.

Utilization of the "sunday start" method for oral contraceptive therapy can result in the initiation of oral contraceptive administration as late as day 6 of the ovarian/menstrual cycle. Potentially, "breakthrough" ovulations could occur due to rapid follicular progression, especially if the dominant follicle is overtly established prior to the onset of estrogen-progestin administration. Here, we examined the efficacy of two new oral contraceptive regimens on potential "breakthrough" ovulations in the first cycle of treatment begun on cycle days 1 or 6 in cynomolgus monkeys having normal menstrual cycles. Our endocrine findings show that follicular recruitment, and probably selection of the dominant follicle, had occurred by day 6 of the follicular phase. Both oral contraceptive treatments (Loestrin 5/7/9R, LoDose 5/7/9R, Parke-Davis) were effective in blocking preovulatory-like gonadotropin and estradiol surges as well as luteal phase progesterone elevations, whether treatment was begun on day 1 or day 6 of the menstrual cycle. Despite hormonal evidence of significant maturational progression, oral contraceptive administration successfully blocked the completion of follicular maturation, thereby sustaining contraceptive reliability, even in the initial cycle of treatment using a "sunday start" regimen. Under these conditions, dissolution of the failed dominant follicle within ovarian stroma may be characterized by delayed follicular atresia.

Animals↗

PubMed1989

Probing studies on multiple dose effects of antide (Nal-Lys) GnRH antagonist in ovariectomized monkeys.

This study was designed to extend evaluation of the long-acting effects of a "third generation" Antide (Nal-Lys) GnRH antagonist on gonadotropin secretion in ovariectomized (OVX) monkeys, with special attention to recrudescence of pituitary gonadotropin secretion after multiple dose treatments, as well as pituitary secretory responsiveness to GnRH. The duration of FSH/LH inhibition by Antide was dose-dependent, as well as being much longer than for Nal-Glu GnRHant; however, full recrudescence of gonadotropin secretion, albeit gradual, did occur. The acute LH secretory response to serial iv boluses of GnRH, in the face of GnRHant-induced suppression of gonadotropin secretion, was transiently accelerated and biologically active. Thereafter, the state of FSH/LH inhibition was resumed chronically. Thus, treatment with Antide produced profound long-term inhibition of tonic gonadotropin levels, yet hyper-responsiveness to exogenous GnRH administration was maintained throughout.

Animals↗

PubMed1989

Effects of ovarian tissue reduction on the menstrual cycle: persistent normalcy after near-total oophorectomy.

These experiments were designed to evaluate whether removal of approximately 95% visible ovarian tissue would interrupt the short- or long-term regulation of cyclic ovarian function. On cycle Days 2 4 (onset of menses = Day 1), the entire left ovary and approximately 90% of the right ovary were removed from three cycling cynomolgus monkeys. After approximately 95% ovariectomy, there was an acute elevation of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which lasted 11 +/- 2 days. A midcycle-like gonadotropin surge occurred 20 +/- 3 days following approximately 95% ovariectomy; the next menses occurred 19 +/- 1 days later. Follicular phase patterns of estradiol preceded the midcycle gonadotropin surge, and luteal phase progesterone levels indicated subsequent ovulation. Two of three monkeys resumed normal menstrual cyclicity in the following cycle with follicular phase, luteal phase, and menstrual cycle lengths similar to pretreatment levels. Histological examination of the ovarian remnant removed on Day 21 of the next cycle revealed a morphologically normal corpus luteum and many small follicles. A second group of 6 rhesus monkeys also underwent approximately 95% ovariectomy for long-term evaluation of menstrual cyclicity; typical 28-day menstrual cycle patterns were observed in 4 of the 6 monkeys for 5 mo, with 2 of these 3 animals maintaining regular menstrual cycles for 1 yr. In summary, our data suggest that normal ovarian function, i.e. recruitment, selection, and dominance of the ovulatory follicle, ovulation, and subsequent corpus luteum function, is maintained with only approximately 5% of functional ovarian tissue remaining.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1989

Gonadotropin-releasing hormone infusion interval: importance in pharmacodynamics.

Circulating gonadotropin-releasing hormone (GnRH) levels were measured during and after intravenous infusion intervals ranging from 0.08 minutes to 5 minutes and doses ranging from 1 to 25 micrograms per pulse. In all dose groups (1 vs. 5 vs. 25 micrograms), the peak levels of GnRH decreased from the 0.08 minute to the 5 minute infusion interval. Our results suggest that the infusion interval over which GnRH is administered has profound effects on the amount, duration, and pattern of GnRH measured in the peripheral circulation.

Animals↗

PubMed1988

Characterization of recombinant DNA derived-human luteinizing hormone in vitro and in vivo. Efficacy in ovulation induction and corpus luteum support.

The present data are the first, to our knowledge, to demonstrate the production feasibility of a commercially available medication of pure human luteinizing hormone from recombinant DNA technology (rechLH). The rechLH preparation achieved ovulation induction and corpus luteum support in the primate menstrual cycle. The observations described herein indicate the opportunity for significant improvement in the treatment of infertile women and men who require gonadal stimulation. Recombinant DNA-derived gonadotropin products, rechLH in this case, will have several therapeutic advantages compared with current medications extracted from urine. These advantages include (1) better reliability of an available supply of hormone and (2) improved treatment flexibility in determining the optimal dose ratio of follicle-stimulating hormone and luteinizing hormone or avoidance of the long-acting effects of human chorionic gonadotropin, as the needs of individual patients may dictate.

Animals↗