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G D Hodgen

Publications and source records attributed to G D Hodgen.

At least 19 recordsLinked to original sources
PubMed1998

Screening for antiproliferative actions of mifepristone. Differential endometrial responses of primates versus rats.

This laboratory has previously shown the capability of the antiprogestin, mifepristone, to noncompetitively inhibit estrogen-induced endometrial proliferation in nonhuman primates. In the following study, use of the rat uterine weight bioassay was compared against a primate (Macaca fascicularis) uterine bioassay to identify the noncompetitive/antiproliferative effects of mifepristone. These uterine bioassays were contrasted for reasons of identifying a comparative laboratory rodent model that could substitute for the need to use primate models in the screening of potential antiprogestins, thereby saving time, cost, and primate resources. Results of the primate experiment showed that mifepristone decreased endometrial proliferation in a dose-dependent manner; importantly, this decrease occurred in the presence of sustained physiologic serum 17 beta-estradiol (E2) levels. However, in the rat model, results showed that mifepristone altered uterine wet weight and blotted weight values only in those animals receiving pharmacological doses of E2 (p < 0.05). Based on the results summarized herein, use of this rat uterine weight bioassay as a substitute for primate models is not recommended for screening and identification of "interesting" antiprogestins. Apparently, the endometrial noncompetitive antiestrogenic/antiproliferative effects of mifepristone, observed repeatedly in these laboratory primates, do not operate in the rat uterine tissue.

Animals↗
PubMed1998

Chronic antiprogestin therapy produces a stable atrophic endometrium with decreased fibroblast growth factor: a 1-year primate study on contraception and amenorrhea.

OBJECTIVE: To describe the efficacy of mifepristone in the prevention of menstrual bleeding and ovulation, with similar observations in comparison groups. DESIGN: Prospective experimental study. Thirty-two cynomolgus monkeys were divided equally into four treatment groups (n = 8). Treatment lasted for 1 year. INTERVENTION(S): Group I received GnRH-agonist (GnRH-a) and in-sequence mifepristone, group II received mifepristone only, group III received GnRH-a only, and group IV received vehicle control. MAIN OUTCOME MEASURE(S): Serum estradiol and progesterone, menstrual bleeding, endometrial thickness, and endometrial expression of basic fibroblast growth factor (bFGF) as determined by immunohistochemistry. RESULT(S): Weekly progesterone determinations showed that mifepristone-treated monkeys seldom ovulated (6 ovulations in 8 years), compared with the controls (100 ovulations in 8 years), while maintaining early to midfollicular levels of circulating serum estradiol. The GnRH-a-only group also rarely ovulated, but was chronically and severely hypoestrogenic. The mifepristone-only group showed scant menstrual bleeding (5 days in 8 years) as compared with the menstrual frequency in control animals (422 days in 8 years). Endometrial proliferation, as determined by biopsy, was similarly minimal for both the GnRH-a and mifepristone groups, and statistically less than in control monkeys. Both the mifepristone and GnRH-a treatments suppressed endometrial gland expression of the angiogenesis polypeptide bFGF. CONCLUSION(S): Chronic mifepristone induced anovulation along with virtual amenorrhea, which suggests the worth of this novel hormonal contraceptive.

Amenorrhea↗
PubMed1997

Vascular endothelial growth factor in primate endometrium is regulated by oestrogen-receptor and progesterone-receptor ligands in vivo.

We investigated hormonal regulation of endometrial angiogenesis in menstruating primates. This study was designed to demonstrate: (i) that cell-specific vascular endothelial growth factor (VEGF) production and expression in monkey endometrium are regulated by steroid receptor ligands; and (ii) mifepristone (RU 486) alters VEGF production even in the absence of a progestin agonist. Endometrial VEGF production was compared by computer-assisted immunohistochemical analysis during induced hypoestrogenism and after oestradiol, progestin, or antiprogestin (mifepristone) treatment. VEGF gene expression was estimated by quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) in endometrial samples from castrate cynomolgus monkeys, from intact monkeys in the luteal phase, and from monkeys treated for 20 days with levonorgestrel (LNG) or mifepristone. VEGF staining intensities in glandular epithelium and VEGF mRNA expression were highest in hypoestrogenic monkeys. Progestin treatment induced intense VEGF staining in the stroma. Gene expression of VEGF-189, but not other isoforms, was higher in progesterone- and progestin (LNG)-exposed endometria compared to mifepristone-exposed endometria or endometria from anovulatory cycles (P < 0.04). Mifepristone abolished VEGF staining in glandular epithelium almost completely. We conclude that VEGF protein and VEGF mRNA expression levels in primate endometrium depend on the steroidal milieu. Anti-angiogenic effects of mifepristone via suppression of VEGF production might represent a mechanism for its quelling effects on endometrium.

Animals↗
PubMed1996

Multiple transcription start sites for the GnRH gene in rhesus and cynomolgus monkeys: a non-human primate model for studying GnRH gene regulation.

In humans, transcription of the gonadotropin-releasing hormone (GnRH) gene can be initiated at two transcription start sites to produce different GnRH mRNAs. The upstream transcription start site is used only in reproductive tissues and tumors. To determine if a similar pattern of GnRH gene expression exists in non-human primates, we cloned GnRH cDNA from rhesus monkey hypothalamic RNA using reverse transcriptase-polymerase chain reaction (RT-PCR) and the 5' flanking region of the monkey GnRH gene by PCR. A 96% similarity between monkey and human GnRH cDNA was found with 94% similarity in the upstream promoter region. An upstream transcriptional start site, was identified in cynomolgus monkey testicular mRNA, 504 base pairs upstream from the hypothalamic site, which was different from that identified in the human GnRH gene. Various cynomolgus monkey reproductive tissues were found to utilize this upstream transcriptional start site. In contrast, no evidence was found for the use of upstream transcriptional start sites in rat testis or placenta, suggesting that the reproductive tissue specificity of the upstream transcription start site may be a primate specific feature.

Amino Acid Sequence↗
PubMed1996

Effects of caffeine and dbcAMP on zona pellucida penetration by epididymal spermatozoa of cynomolgus monkeys (Macaca fascicularis).

Spermatozoa mature during epididymal transit, acquiring the abilities to swim progressively, fertilize oocytes, and produce viable offspring. In this study, we investigate the capacity of spermatozoa retrieved from the midcorpus and distal cauda regions of the epididymis of the cynomolgus monkey to penetrate homologous zona pellucida. Successful in vitro fertilization by ejaculated macaque sperm is dependent upon the addition of caffeine and dbcAMP. Therefore, the effect of these cyclic nucleotide mediators was also examined in this study. Results of sperm motion analysis indicate no difference in baseline values (without stimulators) for any motion parameter. With the addition of caffeine and dbcAMP, curvilinear velocity significantly increased only for the distal cauda sperm (P = 0.05). Amplitude of the lateral head displacement was significantly increased for distal cauda sperm (P < 0.01); although elevated above baseline, the increase observed after activation by corpus sperm was significantly lower than that achieved by cauda sperm (P < 0.05). The addition of caffeine and dbcAMP was an absolute requirement for zona penetration by both midcorpus and distal cauda sperm. With activation, zona penetration was significantly decreased for corpus sperm compared to cauda sperm (P < 0.001). These results suggest that cynomolgus monkey sperm reaching the midcorpus region of the epididymis have not completed all of the maturational changes requisite for successful fertilization; this immaturity is evidenced by decreased sperm motion and by impedance at the level of zona penetration.

Animals↗
PubMed1996

Inhibition of ovulation by progestin analogs (agonists vs antagonists): preliminary evidence for different sites and mechanisms of actions.

Continuous administration of the antiprogesterone RU486 inhibits ovulation in women and in monkeys; in this regard RU486 may act as a progestin agonist rather than as an antagonist. We compared the site(s) and mechanism(s) of RU486-induced ovulation inhibition with those of levonorgestrel (LNG). Six regularly menstruating cynomolgus monkeys each received placebo, RU486 (1 mg/kg/d) or LNG (2 g/kg/d) i.m. between days (cd) 2-22 of three separate menstrual cycles. Serum levels of estradiol (E2), progesterone (P4), androstenedione, LH and FSH were analyzed by RIAs in daily blood samples. Basal and GnRH-stimulated (1 and 50 g of GnRH i.v. 2 h apart) secretion of LH and FSH was assessed using serial blood samples collected for 12 h on cd 10. Mean cycle length was prolonged by RU486 and LNG treatments from 32 d to 70 d and 52 d, respectively (p < 0.02). Ovulation was inhibited in five of the six primates during RU486, and in all six during LNG treatment. During RU486 treatment, serum E2 levels were similar to those of the control cycle; despite peaks of E2 secretion, no LH peaks were seen. In contrast, E2 concentrations were profoundly suppressed during LNG treatment (p < 0.005). The reduction in serum E2 was accompanied by lower levels of androstenedione, and suppressed ratio of E2/androstenedione (p < 0.02) suggesting both reduced synthesis and aromatization of androgen precursors during administration of LNG. Consequently, LNG treatment was associated with higher levels of serum FSH and LH (p < 0.001; 1-way ANOVA). Similarly, as during the luteal phase of the menstrual cycle, the amplitude of basal LH-pulses was increased during LNG treatment (p < 0.05), whereas RU486 treatment did not affect basal LH secretion. The GnRH-stimulated release of LH was similar during the placebo, RU486 and LNG cycles; enhanced release of FSH was seen during administration of LNG. Thus, in the present model system, RU486 seems to inhibit ovulation mainly at the level of hypothalamus, possibly by interfering with the steroidal positive feedback signals from the ovary. However, LNG inhibits ovulation differently, most likely via direct progesterone-like effects on folliculogenesis and the hypothalamus. The pituitary does not appear to be the major site of action(s) of RU486 or LNG. Thus, the differential mechanisms of ovulation inhibition by RU486 and LNG seem to result from lesser intraovarian impact of RU486 as well as dissimilar influences on tonic gonadotropin secretory levels. We conclude that when inhibiting ovulation, RU486 does not act as a progestin agonist, but rather, functions through a hypothalamic mechanism(s), which might be unique to RU486 as a progesterone antagonist.

Analysis of Variance↗
PubMed1996

Use of a specific zona pellucida (ZP) protein 3 antiserum as a clinical marker for human ZP integrity and function.

OBJECTIVE: To evaluate binding characteristics of a specific zona pellucida (ZP) protein 3 (ZP3) antiserum to human oocytes in order to determine its usefulness as a clinical marker for human ZP integrity and function and its correlation with IVF outcome. DESIGN: Prospectively designed, blinded, internally controlled study. SETTING: Tertiary care academic center. PATIENTS: Patients undergoing IVF therapy who had either total failed fertilization or partial fertilization were studied. INTERVENTIONS: Metaphase II oocytes showing absence of pronuclear formation were salt stored 48 hours after insemination and bisected into matching hemizonae using micromanipulation. One hemizona was incubated with AS ZP3-6 (an antiserum generated against a synthetic ZP3 peptide derived from an amino acid sequence that is highly conserved in the structure of ZP3), whereas the matching hemizona was incubated with AS ZP3-7, an antiserum detecting exclusively mouse ZP3 (internal, negative control). Antibody binding was visualized using the peroxidase-antiperoxidase method and diaminobenzidine as color reagent. RESULTS: A total of 104 unfertilized oocytes were evaluated. Analysis of variance showed a significant interaction between gamete factor groups (sperm and oocyte) and antiserum factor. Patients with oocyte factor had significantly lower mean staining scores for the AS ZP3-6-treated hemizonae than patients with sperm factor. CONCLUSIONS: These results demonstrate that anomalies of human ZP3 can be identified with AS ZP3-6 and that these ZP abnormalities correlate with fertilization failure during IVF treatment. Thus, this newly developed biomarker may be of clinical significance in the identification of oocyte defects that are associated with fertilization disorders and may help in the decision-making process in the IVF-assisted fertilization setting.

Adult↗
PubMed1996

Ectopic growth of endometrium depends on its structural integrity and proteolytic activity in the cynomolgus monkey (Macaca fascicularis) model of endometriosis.

OBJECTIVE: To identify factors influencing the development of endometrial autografts in a monkey model of endometriosis. DESIGN: Prospective, comparative study. SETTING: Animal research unit. SUBJECTS: Thirty regularly cycling cynomolgus monkeys in three groups of 10 each. INTERVENTIONS: Endometrium was minced and spilled into the cul-de-sac in group 1. In group 2, the tissue additionally was digested enzymatically. In group 3, the tissue was incubated with a protease inhibitor. MAIN OUTCOME MEASURES: Staging laparotomies after 3 weeks and 3 months. RESULTS: In groups 1, 2, and 3, moderate or severe disease was seen in eight, two, and four monkeys, respectively, after 3 weeks and in eight, three, and two monkeys, respectively, at 3 months. CONCLUSIONS: An intact structure leads to ectopic implantation of endometrial fragments in most cases. Conversely, enzymatic digestion of endometrial fragments and treatment with proteinase inhibitor impair ectopic growth. Intrinsic endometrial factors that influence extracellular matrix remodeling may play a role in the pathogenesis of human endometriosis.

Animals↗
PubMed1996

Endometrial effects of RU486 in primates--antiproliferative action despite signs of estrogen action and increased cyclin-B expression.

Continuous antiprogestin administration to hormone replaced, castrate monkeys inhibits estrogen-induced endometrial proliferation through mechanisms which remains unclear. To elucidate the molecular mechanisms of RU486-induced endometrial suppression, we treated six intact female cynomolgus monkeys on cycle days 2-22 sequentially with placebo, RU486 (1 mg/kg/day) and levonorgestrel (LNG) (2 microg/kg/day) intramuscularly (i.m.), with uterine wedge sections and endometrial biopsies collected on day 22 of each cycle. The uterine sections were evaluated for morphology, mitosis and proliferating cell nuclear antigen (PCNA) immunohistochemistry. Changes in the mRNA levels of ER, PR, cyclin-B and tumour suppressor gene p21 were assessed using co-amplification with beta-actin by reverse transcriptase-polymerase chain reaction (RT-PCR). Administration of RU486 uniformly resulted in characteristic suppression of endometrium with few mitosis, dense stroma and simple glands, whereas the effects of LNG were less uniform. Following RU486 administration, the levels of endometrial ER and PR mRNA were comparable to proliferative phase endometrium, and significantly higher than those seen in the secretory endometrium, indicating that some of the biological actions of E2 were not inhibited during RU486 treatment. Despite scarce mitosis, PCNA was readily detectable in all samples. Curiously, in comparison to secretory phase controls, the levels of cyclin-B, but not p21, mRNA were markedly increased following RU486. The effects of LNG on the levels of these mRNA species varied, with mean levels falling between those of the secretory phase controls, and RU486-treated specimens. The increase in cyclin-B mRNA and lack of mitosis suggests that anti-proliferative actions of RU486 in the primate endometrium might be associated with a cell-cycle block at the G2-M interphase. Whether mechanisms similar to these are associated with the beneficial clinical effects of RU486 seen in the treatment of various hormone dependent maladies remains to be determined.

Animals↗
PubMed1996

Non-competitive anti-oestrogenic actions of progesterone antagonists in primate endometrium: enhancement of oestrogen and progesterone receptors with blockade of post-receptor proliferative mechanisms.

Previous studies have shown that the progesterone antagonists (antiprogestins) inhibit oestrogen-dependent endometrial proliferation in ovariectomized monkeys, without having affinity to the oestrogen receptor (ER). This study was designed to investigate the effect of the antiprogestins mifepristone (RU 486) and onapristone (ZK 98,299), on the concentration of ER and progesterone receptor (PR) in the endometrium of long-term ovariectomized cynomolgus monkeys (Macaca fascicularis). In untreated monkeys, tissue preparations bound in total 228 +/- 68 pmol [3H]-oestradiol/g protein (ER), and 119 +/- 42 pmol [3H]-R5020/g protein (PR). These values were not significantly different from the total binding capacities of tissues from monkeys treated with RU 486 alone or primates treated with oestradiol plus progesterone. Treatment with oestradiol alone almost doubled the ER and PR concentrations. Combined treatment with oestradiol and RU 486 enhanced the ER and PR concentrations in a dose-dependent manner: 1 mg/kg body weight (bw) RU 486/kg increased both ER and PR contents about 3-fold. The dose of 5mg/kg bw RU 486 or onapristone increased the ER and PR concentrations almost 6- and 5-fold respectively, compared with the oestradiol-treated controls. Our results demonstrate that RU 486 and onapristone increased the endometrial ER and PR concentrations far beyond the physiological level in ovariectomized, oestradiol-treated monkeys. Whether the over-expression of ER and PR in the presence of antiprogestins is causally related to the antiproliferative impact of antiprogestins in the endometrium (non-competitive anti-oestrogenic effects) or is an independent action in unknown.

Animals↗
PubMed1996

Antiprogestin and/or gonadotropin-releasing hormone agonist for endometriosis treatment and bone maintenance: a 1-year primate study.

The fact that RU 486 curtailed estrogen-induced endometrial proliferation in primates and relieved pelvic pain in women with endometriosis is the reason for continuing research on antiprogestins. Thirty-two adult female cynomolgus monkeys demonstrating menstrual regularity had surgery for the induction of endometriosis. After lesion staging, four treatment groups (n = 8), each of 1-yr duration, were made. Group I received combination/sequential therapy with depot GnRH agonist (GnRH-a) for 3 months, followed by weekly RU 486 for 9 months. Group II received weekly RU 486, group III received monthly GnRH-a, and group IV served as a vehicle control. A staging laparotomy was performed every 3 months to assess the area of peritoneal endometriosis (square centimeters) and the thickness of in situ endometrium. Bone density was measured serially by dual x-ray absorptiometry. Serum was collection weekly. Mean (+/- SE) serum estradiol levels were lower after GnRH-a (77.1 +/- 2.6 pmol/L) than after RU 486 (231 +/- 12 pmol/L) treatment and lower than those in untreated cycling controls (231 +/- 13 pmol/L). GnRH-a produced significant atrophy of endometriotic plaques within 3 months of therapy; this lesion reduction was sustained with RU 486. Both GnRH-a and RU 486 alone produced profound thinning of ectopic and eutopic endometrium throughout 1 yr of continuous therapy. Bone density decreased significantly after 6 months of GnRH-a alone (P < 0.05), without significant changes in the other groups. After RU 486 treatment, there were no significant changes in testosterone, androstenedione, sex hormone-binding globulin, or cortisol. Like GnRH-a, long term antiprogestin therapy produced a reduction in the volume of pelvic endometriotic lesions as well as atrophy of in situ endometrium; however, RU 486 allowed maintenance of tonic ovarian estradiol secretion, suggesting that efficacious endometriosis therapy can be sustained long term without the sequelae of hypoestrogenism, specifically bone density loss.

Animals↗
PubMed1996

Antiproliferative effects of low-dose micronized progesterone.

OBJECTIVE: To study the pharmacodynamic effects of oral micronized P on endometrial maturation. DESIGN: This was a controlled, open, parallel group, pilot study. SETTING: The experiment was performed in an outpatient academic clinical research unit. PATIENTS: Twelve healthy, P-challenged, estrogen-primed, postmenopausal women participated in the study. INTERVENTIONS: Patients were given 300 mg micronized P daily (8:00 A.M.) or twice (8:00 A.M. and 4:00 P.M.) daily from study days 1 through 14 after estrogen priming for 30 days. Blood samples were taken at 0, 0.5, 1, 1.5, 2, 3, 4, 6, and 8 hours after the 8:00 A.M. dose on study day 1 and 14 and again at 8:00 and 9:30 A.M. on days 3 and 5 fasting, days 7 and 9 after a fatty meal, and day 11 after a high fiber meal. Endometrial biopsies were taken on day 1 and 14. MAIN OUTCOME MEASURES: Progesterone concentrations were measured. Endometrial biopsies were studied for effects on histology, glycogen content of glands, ribosomal RNA, and nuclear estrogen receptors in glands, surface epithelium, and stroma. RESULTS: Day 1 and 14 P kinetics were similar for 8 hours. Dose-dependent increases in glandular glycogen, decrease in ribosomal RNA, and decrease in nuclear estrogen receptors were demonstrated. CONCLUSIONS: Oral micronized P can induce antiproliferative changes in the human endometrium at doses lower than those required for transformation of the endometrium to a full secretory state.

Cell Division↗
PubMed1996

The effect of coculture on the postfertilization development of in vitro-matured monkey oocytes.

OBJECTIVE: To determine if the developmental potential of embryos resulting from in vivo- and in vitro-matured monkey oocytes could be increased through the use of a coculture system. DESIGN: Randomized prospective comparison of embryos resulting from either in vitro- or in vivo-matured oocytes cocultured with Vero cells or cultured in medium alone (control). SETTING: Basic research laboratory. MAIN OUTCOME MEASURES: In vitro embryo development to the blastocyst stage and blastocyst hatching. RESULTS: No significant difference in development was noted between coculture and control groups with embryos resulting from in vivo-matured oocytes. However, coculture was found to improve significantly the development of monkey embryos resulting from in vitro-matured oocytes. CONCLUSIONS: These results demonstrate that primate embryos resulting from in vitro-matured and in vitro-fertilized oocytes differ in their culture requirement when compared with embryos resulting from in vivo-matured oocytes.

Animals↗
PubMed1996

Role of hypoestrogenism or sex steroid antagonism in adhesion formation after myometrial surgery in primates.

OBJECTIVE: To determine the contribution of estrogen in the development of pelvic adhesions during myometrial surgery. DESIGN: A randomized, prospective study in the nonhuman primate. SETTING: A primate colony, Department of Obstetrics and Gynecology, Eastern Virginia Medical School. INTERVENTIONS: All primates were assigned prospectively to one of three treatment groups: [1] GnRH analogue (GnRH-a), [2] mifepristone, or [3] vehicle control. After 3 months of treatment, a standard uterine fundal hysterotomy, for full thickness endometrial biopsy, was performed at the time of exploratory laparotomy, with subsequent scoring of utero-omental adhesions to the hysterotomy site at a future staging procedure based upon adhesion area, vascularity, and tenacity. Serum was drawn on the day of surgery for E2 determination. Endometrial height, from the surface interface between the endometrium and myometrium, was used as a bioassay of estrogen activity. RESULTS: The hypoestrogenic (GnRH-a) group and the mifepristone group had significantly fewer utero-omental adhesions compared with the normally cycling control monkeys as measured by a lower adhesion score. Similarly, the endometrial thickness was significantly reduced in the GnRH-a and mifepristone groups (one-third) compared with the cycling controls, demonstrating the effects of either hypoestrogenism or noncompetitive estrogen antagonism. Serum E2 on the day of surgery was predictive of the postoperative adhesion score by both a regression analysis and analysis of covariance. CONCLUSIONS: The actions of E2 seem to have a dramatic effect on the formation of pelvic adhesions after myometrial surgery.

Animals↗
PubMed1995

Activation of the hypothalamo-anterior pituitary corticotropin-releasing hormone, adrenocorticotropin hormone and beta-endorphin systems during the estradiol 17 beta-induced plasma LH surge in the ovariectomized monkey.

The present work describes time-dependent changes in the content of corticotropin-releasing hormone (CRH), adrenocorticotropin (ACTH), and beta-endorphin (beta-EP) in the hypothalamus (HT) and anterior pituitary (AP) and in the concentration of ACTH and beta-EP in the plasma during the 17 beta estradiol (E2) benzoate (E2B)-induced luteinizing hormone (LH) surge in ovariectomized cynomolgus monkeys. Monkeys were euthanized at 0, 30, 48, 72, and 96 hr post-E2B. HT and AP were rapidly dissected, extracted in 2 N acetic acid containing 1 mM phenylmethane sulfonyl fluoride at 4 degrees C, and centrifuged at 18,000g for 30 min. Peptide concentrations were measured in the supernatant by specific radioimmunoassays (RIAs). In the HT, there were significant (P < 0.05) decreases in ACTH and beta-EP content by 30 hr post-E2B and a significant (P < 0.05) decrease in HT CRH content 48 hr post-E2B. Thereafter, CRH, ACTH, and beta-EP content increased up to 72 hr post-E2B. In the AP, there was an almost linear decrease in the CRH content through 48 hr post-E2B followed by a marked 20-fold (P < 0.01) increase in the AP CRH content at 72 hr post-E2B, which corresponds to the time of the descending arm of the LH surge. The patterns of ACTH and beta-EP content were very similar in the AP, while that of CRH differed markedly. In contrast, in the HT CRH, ACTH, and beta-EP profiles were very similar. Significant (P < 0.05) increases in circulating levels of ACTH, beta-EP, and cortisol were evident at 30 hr (all 3 hormones), 48 hr (beta-EP and cortisol), and 72 hr (cortisol) post-E2B, which corresponds with the time of decreased hypothalamic content of CRH, ACTH, and beta-EP. These results suggest that there maybe a marked activation of the hypothalamo-anterior pituitary-adrenal axis during the negative and positive feedback phases of the E2B-induced LH surge in the ovariectomized monkey.

Adrenocorticotropic Hormone↗
PubMed1995

Mechanism for species-specific induction of Leydig cell tumors in rats by lansoprazole.

Lansoprazole is a substituted benzimidazole which inhibits gastric acid secretion by inhibiting the hydrogen-potassium ATPase (proton pump) in the parietal cell. The finding of Leydig cell hyperplasia and Leydig cell tumors in 2-year oral studies in Sprague-Dawley rats but not in CD-1 mice prompted investigative studies to determine the mechanism for the Leydig cell changes. hCG challenge studies in Sprague-Dawley rats revealed decreased testosterone responsiveness in rats treated orally for 1 or 2 weeks with lansoprazole. After 4 weeks of daily oral treatment increases in serum LH and decreases in serum testosterone were detected within a few hours after dosing. In a study where 9-month-old male F344 rats were given testosterone supplementation via Silastic implants and then treated with lansoprazole for 6 months, a high incidence of Leydig cell tumors was seen in lansoprazole-treated, unsupplemented rats, whereas no Leydig cell tumors were seen in testosterone supplemented rats. This implied that reduction of the normal feedback inhibition at the level of the hypothalamus and/or pituitary due to reduced testosterone levels, thus giving rise to elevated levels of LH, was involved in the induction of Leydig cell tumors by lansoprazole. In vitro studies with Leydig cells from rats using various stimulators and precursors of testosterone biosynthesis demonstrated that the most sensitive site for inhibition of testosterone synthesis by lansoprazole is the transport of cholesterol to the cholesterol side chain cleavage enzyme. The IC50s for inhibition of LH or hCG-stimulated testosterone synthesis in Leydig cells from rats, mice, and monkeys were 11-12, 8, and 24.7 micrograms/ml, respectively. In vitro studies with metabolites of lansoprazole revealed that three metabolites were more potent inhibitors of testosterone synthesis than the parent drug, two of them being at least 10 times more potent. These metabolites are present in rats at substantial levels but are undetectable in humans. The lack of induction of Leydig cell tumors in mice, lower sensitivity of primate Leydig cells, and the absence of testosterone synthesis-inhibiting metabolites in man suggest that Leydig cell tumors found in rats represent a species-specific sensitivity and does not imply a risk for clinical use in man.

2-Pyridinylmethylsulfinylbenzimidazoles↗
PubMed1995

Estrogen and progesterone receptor mRNA are expressed in distinct pattern in male primate reproductive organs.

PURPOSE: The role(s) of estrogens (E) and progesterone (P) in male reproductive physiology remain unclear. Estrogens are used in the treatment of prostatic cancer. Progestins have been used to control excessive sexual behavior in men, and proposed as a male contraceptive. Previous immunohistochemical studies have shown that E receptors (ER) are present in the reproductive tract of male nonhuman primates. METHOD: We examined the expression pattern of ER and progesterone receptor (PR) mRNA in adult primate male reproductive tract. mRNA was extracted from male pituitary, testis, prostate and different regions of the epididymis of three intact adult cynomolgous monkeys. Ovarian, myometrial and spleen mRNA were used as controls. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to amplify ER and PR mRNA; beta-actin mRNA was used as a reference. Primers for ER, PR and beta-actin were designed using the most conserved areas in the corresponding human cDNA sequences, and the identity of the PCR products was verified using Southern hybridization. Semiquantitative analysis of ER and PR mRNA content in different parts of the male reproductive tract was carried out by spiking the PCR reaction with 33P-dCTP, and amplifying the samples for 20 cycles with the beta-actin primers, whereas 30 cycles were used for ER and PR. RESULTS: The results are expressed as cpm ratios of ER or PR/beta-actin. All the male reproductive organs studied revealed a strong signal for ER and PR mRNA. The results of the semiquantitative analysis indicate that the expression of both ER and PR was highest in testis (mean +/- SE 6.4 +/- 1.3 and 0.5 +/- 0.1, respectively). The mean figures for prostate were 0.5 and 0.4, respectively. The mean content of ER and PR in the different areas of epididymis was 0.5 and 0.1, respectively. The epididymal ER mRNA was highest in the corpus region (ER/beta-actin 0.7), the ratio being 0.4 for the caput and cauda regions. The expression pattern of PR mRNA was different, and the caput of epididymis being the most intense (0.2). Surprisingly, the pituitary content of ER and PR mRNA was close to that seen in the ovary, the mean +/- SE values being 7.6 +/- 0.5 and 1.3 +/- 0.1, respectively. CONCLUSIONS: We, therefore, conclude that male monkey reproductive tract contains mRNA for ER and PR, and there appears to be regional variation in their expression. Thus the role(s) of Es and P in male reproductive physiology, specifically in sperm maturation, warrants further investigations.

Actins↗