Gonadotropin uptake in genetic and irradiation models of ovarian tumorigenesis

Genetic and irradiation models of ovarian tumorigenesis were investigated for evidence that elevated gonadotropins have a role in tumorigenesis. Wx/Wv mice lack oocytes at birth, develop complex mesothelial adenomas by 6 mo, and additional ovarian tumor types later. Uptake of iodinated human chorionic gonadotropin (125I-hCG) was measured in mice aged 1 to 30 mo, and uptake iodinated human follicle-stimulating hormone (125I-hFSH) was measured in mice aged 1 to 12 mo. Gonadotropin uptake by Wx/Wv ovaries in vivo declined quickly and was undetectable by 6 mo. Irradiated ovaries rapidly lost oocytes and follicular structures, formed mesothelial adenomas by 5 mo, and later formed additional types of ovarian tumors. In the irradiation model, 125I-hCG uptake also declined quickly and was undetectable by 3 mo of age. Neither the surface nor the tubular epithelium of the mesothelial adenoma were consistently labeled by 125I-hCG in autoradiography studies with either model. Although these data do not exclude an acute role for gonadotropins in initiation of preneoplastic events, they do indicate that ovarian cells do not require chronic gonadotropin stimulation during subsequent tumorigenesis. These findings are discussed in relation to additional models of ovarian tumorigenesis.     

Gonadotropin control of inhibin secretion and the relationship to follicle type and number in the hpg mouse

Inhibin is secreted in two distinct heterodimeric forms, A and B, but the mechanism for the differential control of these two forms is unclear. To evaluate the relationship between secretion of inhibin forms and folliculogenesis, the effects of gonadotropins on inhibin concentrations were studied in parallel with stereological enumeration of ovarian follicle types in gonadotropin-deficient hypogonadal (hpg) female mice treated with recombinant human FSH (10 IU/day), hCG (1 IU/day), or both for 20 days. Treatment with FSH alone significantly increased blood concentrations of both inhibin A and inhibin B, whereas hCG alone had no effect on either inhibin. The combination of FSH and hCG further increased the concentration of inhibin A but had no effect on the concentration of inhibin B beyond that of FSH. The number of primordial follicles per ovary was significantly reduced in FSH-treated hpg mice, but was not affected by hCG treatment. Antral follicles were absent in the untreated hpg mice, present following treatment with FSH, and were present in only limited numbers following hCG treatment alone. Preovulatory follicles were observed only in the wild-type and combined FSH and hCG treatment groups. These results demonstrate that secretion of both inhibins is associated with the presence of antral follicles. Inhibin A secretion is increased by the presence of preovulatory follicles, whereas the concentration of inhibin B is not affected. The observed effects of gonadotropins on inhibin A and B secretion may be explained by corresponding gonadotropin effects on follicle development.     

Ovarian tumorigenesis in mice transgenic for murine inhibin alpha subunit promoter-driven Simian Virus 40 T-antigen: ontogeny, functional characteristics, and endocrine effects

We previously reported formation of ovarian granulosa cell tumors with 100% penetration in a transgenic mouse model with murine inhibin alpha subunit promoter-driven (inhalpha)/Simian Virus 40 T-antigen (Tag). The tumor-bearing inhalpha/Tag mice showed highly elevated serum levels of immunoreactive inhibin. To investigate the onset of tumorigenesis and related endocrine consequences, 6-8 female mice of two inhalpha/Tag lines and their mating control littermates were killed monthly between 1 and 6 mo of age. We also investigated tumorigenesis-related fertility aspects of these two mouse lines. The ontogeny and progression of tumors could be monitored in both inhalpha/Tag lines by alterations of ovarian weights and serum hormone levels. Serum progesterone levels increased in both inhalpha/Tag lines in an age-dependent manner as ovarian tumorigenesis progressed, and a reciprocal decrease occurred in serum LH and FSH. Neither serum estradiol (E(2)) nor uterine weights were significantly altered during tumorigenesis, suggesting that the ovarian tumors represented late stages of granulosa cell differentiation. In conclusion, the present findings show in the inhalpha/Tag TG mice a relation between endocrine consequences of granulosa cell tumorigenesis, and a connection of onset of tumor formation with aberrant steroidogenesis and gonadotropin secretion. These findings indicate that tumors are endocrinologically active and able to exert enhanced negative feedback effects on pituitary function. The tumors provide a good model for endocrinologically active hormone-dependent tumors.     

LH- and FSH-secreting pituitary adenoma in a postmenopausal woman.

Gonadotropin secreting pituitary adenomas have been reported with increasing frequency in men, but they are still rarely recognized in women. We report a 52-year-old postmenopausal woman with LH- and FSH-secreting pituitary adenoma. She had increased LH (37.0 +/- 13.7 IU/l) (mean +/- SD) and FSH (109.9 +/- 26.7 IU/l) but these concentrations were within normal ranges in 80 postmenopausal women (LH: 29.7 +/- 18.3 IU/l, FSH: 104.0 +/- 43.9 IU/l). The administration of GnRH and conjugated estrogen resulted in normal response of LH and FSH. No abnormal response of gonadotropin to TRH and bromocriptine was observed. After transsphenoidal adenomectomy both LH and FSH decreased (LH: 11.1 +/- 4.2 IU/l, FSH: 37.0 +/- 9.6 IU/l). An immunocytochemical study revealed that the adenoma cells synthesize both LH and FSH. The rarity of gonadotropin secreting pituitary adenomas in women could be the result of greater difficulty in recognition due to an increase in serum gonadotropin in postmenopausal women.     

Phosphodiesterase regulation is critical for the differentiation and pattern of gene expression in granulosa cells of the ovarian follicle

Feedback regulations are integral components of the cAMP signaling required for most cellular processes, including gene expression and cell differentiation. Here, we provide evidence that one of these feedback regulations involving the cyclic nucleotide phosphodiesterase PDE4D plays a critical role in cAMP signaling during the differentiation of granulosa cells of the ovarian follicle. Gonadotropins induce PDE4D mRNA and increase the cAMP hydrolyzing activity in granulosa cells, demonstrating that a feedback regulation of cAMP is operating in granulosa cells in vivo. Inactivation of the PDE4D by homologous recombination is associated with an altered pattern of cAMP accumulation induced by the gonadotropin LH/human chorionic gonadotropin (hCG), impaired female fertility, and a markedly decreased ovulation rate. In spite of a disruption of the cAMP response, LH/hCG induced P450 side chain cleavage expression and steroidogenesis in a manner similar to wild-type controls. Morphological examination of the ovary of PDE4D-/- mice indicated luteinization of antral follicles with entrapped oocytes. Consistent with the morphological finding of unruptured follicles, LH/hCG induction of genes involved in ovulation, including cyclooxygenase-2, progesterone receptor, and the downstream genes, is markedly decreased in the PDE4D-/- ovaries. These data demonstrate that PDE4D regulation plays a critical role in gonadotropin mechanism of action and suggest that the intensity and duration of the cAMP signal defines the pattern of gene expression during the differentiation of granulosa cells.     

Regulated expression of sterol carrier protein 2 in the ovary: a key role for cyclic AMP.

Sterol carrier protein 2 (SCP2) is believed to play an important role in the intracellular movement of cholesterol in steroidogenic cells. We examined the distribution of SCP2 gene expression in the rat ovary and the role of gonadotropins and cyclic AMP in the regulation of SCP2 mRNA levels. In situ hybridization revealed that the most steroidogenically active ovarian compartments (e.g., corpora lutea and theca cells) contain significant amounts of SCP2 mRNA whereas granulosa cells have modest levels. Gonadotropins, which promote follicular growth and luteinization, increased the ovarian content of SCP2 mRNA as assessed by Northern blotting along with increases in cytochrome P450scc mRNA. Using steroidogenic transformed rat granulosa cells (Grs-21), a cyclic AMP analogue (8-Br-cAMP) was found to increase SCP2 mRNA and protein levels within 24 h of treatment. P450scc mRNA was also induced whereas actin mRNA levels were not affected. The 8-Br-cAMP stimulation of SCP2 mRNA accumulation was completely inhibited by actinomycin D and cycloheximide. The cyclic AMP analogue also increased SCP2 mRNA levels in a non-steroid hormone producing transformed rat granulosa cell line Gs-8. We conclude that SCP2 gene expression in the ovary is correlated with the state of differentiation of granulosa cells. Gonadotropic hormones which stimulate luteinization of the cells increase SCP2 gene expression. These actions of gonadotropins appear to be mediated at least in part by cyclic AMP through a mechanism requiring ongoing RNA and protein synthesis. However, SCP2 gene expression is not obligatorily coupled to steroidogenic activity, as cyclic AMP analogues can increase SCP2 mRNA in a line of transformed ovarian granulosa cells incapable of synthesizing hormones.     

Regulation of tropomyosin expression in the maturing ovary and in primary granulosa cell cultures

Granulosa cell differentiation in vitro in response to gonadotropins is characterized by major changes in cell shape, cell aggregation, and the organization of microfilaments. These changes are associated with enhanced steroidogenesis in maturing granulosa-lutein cells. Since nonmuscle tropomyosin isoforms were implicated in stabilizing actin filaments, we studied the organization and expression of tropomyosin in differentiating primary cultures of rat granulosa cells and during ovarian folliculogenesis and luteinization. In unstimulated primary granulosa cell cultures tropomyosin was found mainly along stress fibers. In differentiating cells tropomyosin staining was diffuse with sometimes a subcortical organization. The changes in tropomyosin organization were accompanied by a pronounced decrease in the synthesis, translation in vitro, and mRNA levels of all the rat nonmuscle tropomyosin isoforms, with a greater reduction in the higher molecular weight isoforms than in the smaller isoforms. Similar results were obtained whether cells were stimulated to differentiate with gonadotropins, with cAMP, by culturing cells on an extracellular matrix, or by treatment with cytochalasin B. The effect of cytochalasin B was reversible; upon removal of the drug tropomyosin synthesis increased to near control levels, while that of proteins associated with luteinization decreased drastically. RNA isolated from ovaries with follicles at the preantral, preovulatory stage and from corpora lutea contained decreased tropomyosin mRNA levels during ovarian luteinization when the level of RNA for a key steroidogenic enzyme, cytochrome P-450 cholesterol side chain cleavage (P-450 scc), increased. The results suggest a physiological relevance for the low level of tropomyosin expression in the mechanisms which bring about the morphological and biochemical development and maturation of granulosa cells.     

Cell-specific expression and regulation of soluble guanylyl cyclase alpha 1 and beta 1 subunits in the rat ovary

Soluble guanylyl cyclase (sGC) is activated by nitric oxide (NO) and carbon monoxide, resulting in cGMP production. Recent studies indicate that NO and cGMP influence ovarian functions. However, little information is available regarding the ovarian expression of sGC. The present study examined sGC alpha(1) and beta(1) subunit protein levels in the ovary during postnatal development, gonadotropin-induced follicle growth, ovulation, and luteinization as well as in cultured rat granulosa cells. In postnatal rats, sGC alpha(1) subunit immunoreactivity was high in granulosa cells of primordial and primary follicles on Day 5 but low in granulosa cells of larger follicles on Days 10 and 19. Theca cells of developing follicles, but not stromal cells, also demonstrated moderate sGC alpha(1) immunoreactivity. In gonadotropin- treated immature rats, intense sGC alpha(1) subunit staining was similarly observed in granulosa cells of primordial and primary follicles, but such staining was low in granulosa cells of small antral follicles and undetectable in granulosa cells of large antral and preovulatory follicles. Following ovulation, corpora lutea expressed moderate sGC alpha(1) immunoreactivity. Similar ovarian localization and expression patterns were seen for sGC beta(1), indicating regulated coexpression of sGC subunits. Immunoblot analysis revealed no change in total ovarian sGC alpha(1) and beta(1) subunit protein levels during gonadotropin treatment. Similarly, no effect of FSH on sGC subunit protein levels was apparent in cultured granulosa cells. These findings indicate regulated, cell- specific patterns of sGC expression in the ovary and are consistent with roles for cGMP in modulating ovarian functions.     

Mechanisms of regulation of rat ovarian 7,12-dimethylbenz[a]anthracene hydroxylase

The mechanisms of regulation of ovarian 7,12-dimethylbenz[a]anthracene (DMBA) hydroxylase were investigated with respect to hormonal requirements and effects of the antiestrogen tamoxifen and known inducers of cytochrome P-450. The DMBA hydroxylase is increased endogenously about 3-fold in the proestrus phase as compared to the metestrus/diestrus phases (M. Bengtsson and J. Rydstrom, Science, 219 (1983) 1437-1438). A similar effect was caused by the gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) whereas pregnant mare's serum gonadotropin (PMSG) brought about a 3-7-fold increase, suggesting that the estrus cycle-dependence of the DMBA hydroxylase was due directly or indirectly to gonadotropins. In contrast, differentiation of granulosa/theca cells to corpus luteum cells after ovulation, caused by administration of human chorionic gonadotropin (hCG), led to a marked decrease in activity. The activity was not specific for DMBA since substitution of this hydrocarbon for benzo[a]pyrene (BP) as substrate gave similar results. A possible role of estrogens in this context was investigated by the administration of tamoxifen simultaneous with gonadotropin treatment, which caused a partial inhibition of the hydroxylase activity. Both estradiol and 3-methyl-cholanthrene (MC) increased DMBA hydroxylase but the effects of these agents were not additive. In contrast, the effects of estradiol and MC were partially additive to that of gonadotropin. On the basis of these results, it is proposed that the rat ovary contains one or several aryl hydrocarbon hydroxylases located in the granulosa/theca cells which are regulated by estrogens, MC and beta-naphthoflavone (BNF) and that the role of gonadotropins is to proliferate granulosa/theca cells.     

Expression of link protein during mouse follicular development.

To gain insight into the role of link protein in ovarian follicle development, we used immunohistochemistry to determine the patterns of link protein expression in mouse ovary in response to gonadotropin stimulation. Polyclonal antibodies were raised against link protein purified from bovine cartilage. Stimulation of immature mice with gonadotropins increased link protein expression in the granulosa layer of large preovulatory follicles. The number and intensity of immunostained cells increased over 2 hr after hCG injection. Cumulus cells stained link protein mainly in the extracellular matrix, whereas mural granulosa cells showed marked deposits of link protein in the cytoplasm. Link protein expression persisted in luteinized granulosa cells after ovulation and in corpora lutea. Link protein staining was also present in the theca cells and oocytes, which was a consistent finding regardless of gonadotropin treatment. The staining intensity was negated by treatment with hyaluronidase, suggesting that the link protein is bound to hyaluronic acid. On Western blotting, a reacting protein species of about 42 kD was seen in the gonadotropin-treated ovarian extract. The precise cellular distribution of link protein in mouse ovary was determined for the first time by an immunohistochemical method in this study. (J Histochem Cytochem 47:1433-1442, 1999)     

Development of antral follicles in cryopreserved cat ovarian tissue transplanted to immunodeficient mice

Ovarian cortex cryopreservation and xenotransplantation into immunodeficient mice represents a potential means for female germplasm conservation and an immediate model for investigation of folliculogenesis. The objectives of this study were to: (1) assess follicle survival after cryopreservation and transplantation of cat ovarian tissue into non-obese diabetic severely combined immunodeficient (NOD SCID) mice; and (2) evaluate the effects of gonadotropin treatments on follicular development in the transplanted tissue. Slices from the cat ovarian cortex were frozen and after thawing, transplanted under each kidney capsule of castrated male NOD SCID mice (eight xenografts in four mice). Sixty-two days after surgery, mice were randomly assigned (two per group) to gonadotropin-treated (eCG and hCG 88 h later) or control (saline-treated) groups. Twenty-four hours after the last injection, ovarian tissue was recovered and processed for histology. Fresh ovarian tissue from the same original source was similarly processed. Follicles were counted, measured, and classified as primordial, primary, secondary, or antral. Immunoreactive proliferating cell nuclear antigen (PCNA) stain was used to assess follicle viability. Microscopic examination revealed no evidence of necrosis or fibrosis. The grafts were well-vascularized, with follicles at all stages of development. Numbers of follicles in the transplanted tissue were markedly reduced compared to fresh tissue, with approximately 10% of follicles surviving freezing and transplantation procedures. Growing follicles positive for PCNA were found in all xenografts. Gonadotropin treatment did not alter the proportion of resting to growing follicles or mean follicle diameter by comparison with controls from untreated mice. By contrast, luteinization, but not ovulation, of antral follicles was observed only in grafts from treated mice. In summary, frozen-thawed cat ovarian cortex tissue not only survived xenotransplantation, it also contained follicles able to grow to antral stages. Exogenous gonadotropin treatment in this model resulted in luteinization of antral follicles but enhancement of follicular growth and ovulation did not occur.     

Gonadotropin-dependent expression of sterol 14-demethylase P450 (CYP51) in rat ovaries and its contribution to the production of a meiosis-activating steroid.

Immunohistochemical analysis showed that sterol 14-demethylase P450 (CYP51) is expressed in mature follicles and corpus lutea of rat ovaries. In follicles, CYP51 is expressed in granulosa and theca cells but not in oocytes. The ovarian CYP51 activity of hypophysectomized rats is very low and induced by pregnant mares' serum gonadotropin (PMSG) treatment together with ovarian growth. The expression of CYP51 first increases in growing follicles and then appears in the corpus lutea after luteinization. The former event may be due to the follicular-stimulating hormone action of PMSG, and the latter may be caused by the luteinizing hormone effect of PMSG. Sterol analysis indicated that the product of the CYP51-mediated lanosterol 14-demethylation, 4,4-dimethylcholesta-8,14,24-trienol, which has been identified as a meiosis-activating steroid (MAS) in mammals [Byskov et al. (1995) Nature 374, 559-562], accumulates (about 10 pmol/mg of ovary) in mature rat ovaries, and the content is enough to activate the resumption of meiosis. These lines of evidence suggest that the expression of ovarian CYP51 is dependent on gonadotropins, and ovarian CYP51 activity is enough for accumulating MAS. Serum insulin does not affect the ovarian CYP51 level, although it is essential for hepatic CYP51 expression. These findings indicate that expression of CYP51 is regulated differently among organs.     

Evidence for a pituitary site of gonadal steroid stimulation of GnRH receptors in female mice

Treatment of GnRH-deficient (hpg) female mice with oestradiol-17 beta (E2) for 7 days increased GnRH receptors from 4.1 +/- 0.4 fmol/pituitary (control) to 7.2 +/- 0.7 fmol/pituitary (GnRH-treated), and consistently increased pituitary FSH content. Treatment of hpg female mice with E2 plus progesterone (P) for 14 days stimulated GnRH receptors more than did E2 alone, although values still remained lower than those of normal intact female mice. In contrast, GnRH treatment of intact hpg female mice alone, or combined with E2 + P, increased GnRH receptors to values similar to those of intact normal female mice. In contrast, the receptor rise after GnRH treatment alone of ovariectomized hpg mice was significantly less than in intact hpg mice similarly treated. However, the combination of GnRH + E2 + P treatment of ovariectomized hpg mice increased GnRH receptors to normal intact female values, indicating the synergistic actions of these hormones on GnRH receptor up-regulation at the pituitary. Oestradiol treatment of ovariectomized normal female mice prevented the receptor fall after ovariectomy, and when combined with exogenous GnRH further increased receptors to values identical to those of intact female mice receiving GnRH alone. Ovariectomy of hpg mice had no effect on GnRH receptor, serum or pituitary LH and FSH values. There was no change in serum LH concentration after GnRH treatment of hpg female mice, but serum FSH increased and this was accentuated by ovariectomy, indicating that in intact mice an ovarian factor(s) normally inhibits GnRH-stimulated FSH release. This factor did not appear to be an ovarian steroid since serum FSH was not suppressed in intact or ovariectomized GnRH-treated hpg mice concurrently receiving E2 + P treatment. These results suggest that: (1) gonadal steroids alone have a major direct stimulatory action on the pituitary to increase GnRH receptors; (2) the oestrogen-induced increase in GnRH receptors is enhanced in the presence of GnRH; (3) steroids exert inhibitory feedback on gonadotrophin secretion that is mediated at some cellular regulatory locus other than the GnRH-receptor complex.     

Insulin like growth factor 1 and regulation of ovarian function in mammals

Various growth factors have been proposed to play endocrine and/or paracrine role in mammalian ovarian follicular development. The insulin like growth factor 1 (IGF-1) is one such factor. More and more reports now support the existence of an intra-ovarian IGF system including receptors and binding proteins. The role of IGF-1 in ovary is to amplify gonadotropin hormone action in terms of increased steroidogenesis by ovarian granulosa cell and granulosa cell proliferation. The synthesis and proteolysis of insulin like growth factor binding proteins, under the control of follicle stimulating hormone, regulate the intra-follicular availability of IGF-1, which further determines the sensitivity of granulosa cells to gonadotropins. Besides gonadotropins, IGF-1 has been implicated in somatotropin hormone action in the ovarian function. Exact mechanism of IGF-1 action in the ovarian follicles needs to be worked out to elucidate whether or not IGF-1 is indispensable in addition to know endocrine factors like gonadotropic and ovarian steroid hormones. This will pave the way for better understanding of control(s) which ensure final development of dominant follicle(s) and atresia of other follicles of the cohort.     

Characterization of ovarian function in granulocyte-macrophage colony-stimulating factor-deficient mice

During the estrous cycle and early pregnancy, lymphohemopoietic cytokines and chemokines contribute to the regulation of ovarian function by orchestrating the recruitment and activation of leukocytes associated with the ovulatory follicle and corpus luteum. The purpose of this study was to investigate the physiological role of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the ovary, utilizing mice genetically deficient in GM-CSF. Our results show that the mean duration of the estrous cycle in GM-CSF-deficient (GM-/-) mice was extended by 1.5 days (mean +/- SE, 4.9 +/- 0.3 vs. 6.5 +/- 0.5 days for GM+/+ and GM-/- mice, respectively). Similar ovulation rates were observed in immature superovulated mice (31.8 +/- 7.7 vs. 28.9 +/- 6.4 oocytes per mouse) and adult naturally cycling mice (10.4 +/- 0.8 vs. 10.3 +/- 0.8 oocytes per mouse). Furthermore, comparable numbers of oocytes were released from GM+/+ and GM-/- ovaries in an in vitro perfusion model. However, ovaries in pregnant GM-/- mice were found to comprise fewer cells and synthesize less progesterone (141.6 +/- 10.3 vs. 116.5 +/- 6 nM plasma), although the duration of pseudopregnancy was unaltered by GM-CSF deficiency (11.0 +/- 0.2 vs. 11.0 +/- 0.5 days). Immunohistochemical staining of leukocytes in the ovary during the periovulatory period indicated that the size and composition of ovarian leukocyte populations were unaltered in the absence of GM-CSF. However, an effect of GM-CSF deficiency on the activation phenotype of ovarian leukocytes was indicated by a 57% increase in mean secretion of nitric oxide in in vitro-perfused GM-/- ovaries, and diminished major histocompability complex (MHC) class II (Ia) expression in ovarian macrophages and/or dendritic cells (30.5 +/- 7. 2% vs. 9.1 +/- 1.8% positive stain in GM+/+ and GM-/- ovaries, respectively). Furthermore, ovarian macrophages and neutrophils were diminished in number after parturition, with significantly decreased CD11b+ (Mac-1) staining in the stromal region of postpartum GM-/- ovaries (6.7 +/- 0.6 vs. 3.6 +/- 0.7% positive stain). In summary, GM-CSF does not appear to be essential for ovarian function but may play a role in fine-tuning the activation status and adhesive properties of ovarian myeloid leukocytes. Aberrant activation of these cells appears to compromise the luteinization process and the steroidogenic capacity of the corpus luteum during early pregnancy in GM-CSF-deficient mice.     

Tachykinins in the normal and gonadotropin-stimulated ovary of the mouse

In this investigation, substance P (SP) and neurokinin A (NKA) concentrations have been determined in the ovary of control prepubertal mice, and prepubertal mice injected with pregnant mare serum (PMS) gonadotropin, an equine gonadotropin with predominant FSH action, or with PMS followed by human chorionic gonadotropin (hCG), which produces heavily luteinized ovaries after the stimulation with PMS. Control animals were injected with saline. The ovaries of animals treated with gonadotropins were heavier than the control ovaries, the combination of PMS plus hCG produced significantly heavier ovaries than PMS alone. The concentrations of SP and NKA in the ovaries of the animals treated with PMS or PMS/hCG were significantly lower than in control ovaries. No significant differences in ovarian tachykinin concentrations were observed between PMS and PMS/hCG-treated animals. The total ovarian content of SP was lower in PMS-injected animals as compared with the controls. The total ovarian content of NKA was not significantly different in the three groups of animals studied. These results show that ovaries stimulated with gonadotropins have lower concentrations of tachykinins than normal ovaries at the same age. It is therefore evident that gonadotropins can affect tachykinin stores in the ovaries of mice.     

Pituitary and gonadal function in hypogonadotrophic hypogonadal (hpg) mice bearing hypothalamic implants

GnRH receptor values are 30-50% of normal in pituitaries of hpg male mice, and testicular LH receptors only 8% of normal (160.4 +/- 17.6 and 2013 +/- 208.1 fmol/testis respectively). In male hpg mice bearing fetal preoptic area (POA) hypothalamic implants for 10 days there was no change in pituitary GnRH receptors, pituitary gonadotrophin content, or seminal vesicle weight. However, testicular weights and LH receptors were doubled in 4/10 mice and 2 had increased serum FSH levels. Between 26 and 40 days after implantation pituitary GnRH receptors and pituitary LH increased to normal male levels, although at 40 days serum and pituitary FSH concentrations had reached only 50% of normal values. Testicular and seminal vesicle weights increased more than 10-fold by 40 days after implantation and LH receptors to 70% of normal. In hpg female mice bearing hypothalamic implants for 30-256 days pituitary gonadotrophin concentrations were normal, even though GnRH receptors reached only 60% of normal values (6.18 +/- 0.4 and 9.8 +/- 0.4 fmol/pituitary respectively). Serum FSH was substantially increased from values of less than 30 ng/ml in hpg mice to within the normal female range in hypothalamic implant recipients. Ovarian and uterine weights increased after hypothalamic grafting from only 4-5% to over 74% of normal values. LH receptors increased from 6.5 +/- 1.3 fmol/ovary for hpg mice to 566.9 +/- 39.2 fmol/ovary for implant recipients. Vaginal opening occurred about 23 days after implantation and these animals displayed prolonged periods of oestrus.(ABSTRACT TRUNCATED AT 250 WORDS)