Biomedical subjects

P J O'Shaughnessy

Publications and source records attributed to P J O'Shaughnessy.

At least 19 recordsLinked to original sources

PubMed2006

The foetal Leydig cell-- differentiation, function and regulation.

The foetal Leydig cell population arises shortly after testicular differentiation at around 12.5 dpc in the mouse and 6 weeks in the human. These cells function, primarily, to produce androgens which are essential for masculinization of the foetus. The origin of the foetal Leydig cells remains uncertain but it has been suggested that adrenocortical cells and foetal Leydig cells may share a common origin in an adreno-genital primordium. Studies in the mouse are beginning to identify factors such as desert hedgehog and platelet-derived growth factor which are required for foetal Leydig cell development. Regulation of foetal Leydig cell function remains uncertain in most species. Unlike the adult population of Leydig cells, the foetal Leydig cells in the mouse do not require luteinizing hormone (LH) to stimulate androgen production. An intact pituitary does appear to be required, however, and adrenocorticotrophic hormone (ACTH) will stimulate foetal Leydig cell function directly suggesting that both LH and ACTH act to maintain Leydig cell function in vivo. In the human LH/hCG is required for foetal Leydig cell function although the cells may also be sensitive to ACTH.

Animals↗

PubMed2005

Neuroendocrine regulation of Leydig cell development.

During development in the mouse, two populations of Leydig cells arise sequentially. The fetal Leydig cell population arises shortly after testicular differentiation and functions primarily to produce androgens that are essential for masculinization of the fetus. The origin of the fetal Leydig stem cells remains uncertain, but it has been suggested that adrenocortical cells and fetal Leydig cells may share a common origin in an adrenogenital primordium. The fetal Leydig cells require an intact pituitary for normal development and are sensitive to both luteinizing hormone (LH) and adrenocorticotrophic hormone (ACTH). Loss of either one of these hormones does not, however, affect fetal androgen production, suggesting that both LH and ACTH may act to maintain fetal Leydig cell function in vivo in a redundant fashion. The adult Leydig cell population starts to develop soon after birth in the mouse. Initial differentiation does not appear to require gonadotropin input, but subsequent development and function are completely dependent upon LH. The adult Leydig cells do not require circulating follicle-stimulating hormone, provided that LH is present, but androgen stimulation, through the androgen receptor, is required for normal Leydig cell development in the mouse. It is likely that the effects of androgen are mediated directly in the Leydig cells or indirectly through the peritubular cells.

Adrenal Cortex↗

PubMed2004

Changes in mouse granulosa cell gene expression during early luteinization.

Changes in gene expression during granulosa cell luteinization have been measured using serial analysis of gene expression (SAGE). Immature normal mice were treated with pregnant mare serum gonadotropin (PMSG) or PMSG followed, 48 h later, by human chorionic gonadotropin (hCG). Granulosa cells were collected from preovulatory follicles after PMSG injection or PMSG/hCG injection and SAGE libraries generated from the isolated mRNA. The combined libraries contained 105,224 tags representing 40,248 unique transcripts. Overall, 715 transcripts showed a significant difference in abundance between the two libraries of which 216 were significantly down-regulated by hCG and 499 were significantly up-regulated. Among transcripts differentially regulated, there were clear and expected changes in genes involved in steroidogenesis as well as clusters of genes involved in modeling of the extracellular matrix, regulation of the cytoskeleton and intra and intercellular signaling. The SAGE libraries described here provide a base for functional investigation of the regulation of granulosa cell luteinization.

Animals↗

PubMed2003

Identification of developmentally regulated genes in the somatic cells of the mouse testis using serial analysis of gene expression.

To identify genes developmentally regulated in the somatic cells of the testis, serial analysis of gene expression (SAGE) has been used to generate gene expression profiles from these cells in the fetal and adult mouse. To avoid germ cell transcripts, a fetal SAGE library was generated from germ cell-free fetal Wv/Wv mice, and an adult SAGE library was generated from adult testes depleted of germ cells with busulfan. The combined SAGE libraries contained 147570 tags identifying 12976 unique transcripts. Of these transcripts, 3607 were present in only the fetal library and 3941 were present in only the adult library. Most of the abundant differentially expressed tags in the adult testis library were from characterized genes, whereas 3' rapid amplification of complementary ends was required to identify most differentially expressed tags in the fetal library. These fetal tags were mostly associated with uncharacterized UniGene clusters. These data provide a comprehensive and quantitative analysis of gene expression in the somatic cells of the fetal and adult testis (including unknown transcripts) and identify genes differentially expressed in these cells during testis development. These differentially regulated genes are likely to provide insight into mechanisms regulating testis function both during development and in the adult animal.

Animals↗

PubMed2003

Differentiation of adult-type Leydig cells occurs in gonadotrophin-deficient mice.

During mammalian testis development distinct generations of fetal and adult Leydig cells arise. Luteinising hormone (LH) is required for normal adult Leydig cell function and for the establishment of normal adult Leydig cell number but its role in the process of adult Leydig cell differentiation has remained uncertain. In this study we have examined adult Leydig cell differentiation in gonadotrophin-releasing hormone (GnRH)-null mice which are deficient in circulating gonadotrophins. Adult Leydig cell differentiation was assessed by measuring expression of mRNA species encoding four specific markers of adult Leydig cell differentiation in the mouse. Each of these markers (3beta-hydroxysteroid dehydrogenase type VI (3betaHSD VI), 17beta-hydroxysteroid dehydrogenase type III (17betaHSD III), prostaglandin D (PGD)-synthetase and oestrogen sulphotransferase (EST)) is expressed only in the adult Leydig cell lineage in the normal adult animal. Real-time PCR studies showed that all four markers are expressed in adult GnRH-null mice. Localisation of 3betaHSD VI and PGD-synthetase expression by in situ hybridisation confirmed that these genes are expressed in the interstitial tissue of the GnRH-null mouse. Treatment of animals with human chorionic gonadotrophin increased expression of 3betaHSD VI and 17betaHSD III within 12 hours further indicating that differentiated, but unstimulated cells already exist in the GnRH-null mouse. Thus, while previous studies have shown that LH is required for adult Leydig cell proliferation and activity, results from the present study show that adult Leydig cell differentiation will take place in animals deficient in LH.

17-Hydroxysteroid Dehydrogenases↗

PubMed2003

Adrenocorticotropic hormone directly stimulates testosterone production by the fetal and neonatal mouse testis.

Adult Leydig cell steroidogenesis is dependent on LH but fetal Leydig cells can function independently of gonadotropin stimulation. To identify factors that may be involved in regulation of fetal Leydig cells expressed sequence tag libraries from fetal and adult testes were compared, and fetal-specific genes identified. The ACTH receptor [melanocortin type 2 receptor (Mc2r)] was identified within this fetal-specific group. Subsequent real-time PCR studies confirmed that Mc2r was expressed in the fetal testis at 100-fold higher levels than in the adult testis. Incubation of fetal or neonatal testes with ACTH in vitro stimulated testosterone production more than 10-fold, although ACTH had no effect on testes from animals aged 20 d or older. The steroidogenic response of fetal and neonatal testes to a maximally stimulating dose of human chorionic gonadotropin was similar to the response shown to ACTH. The ED(50) for ACTH, measured in isolated fetal and neonatal testicular cells, was 5 x 10(-10) M and the lowest dose of ACTH eliciting a response was 2 x 10(-11) M. Circulating ACTH levels in fetal mice were around 8 x 10(-11) M. Neither alpha-MSH nor gamma-MSH had any effect on androgen production in vitro at any age. Fetal testosterone levels were normal in mice that lack circulating ACTH (proopiomelanocortin-null) indicating that ACTH is not essential for fetal Leydig cell function. Results show that both LH and ACTH can regulate testicular steroidogenesis during fetal development in the mouse and suggest that fetal Leydig cells, but not adult Leydig cells, are sensitive to ACTH stimulation.

Adrenocorticotropic Hormone↗

PubMed2002

Changes in Leydig cell gene expression during development in the mouse.

Developmental changes in the expression of 18 Leydig cell-specific mRNA species were measured by real-time polymerase chain reaction to partially characterize the developmental phenotype of the cells in the mouse and to identify markers of adult Leydig cell differentiation. Testicular interstitial webs were isolated from mice between birth and adulthood. Five developmental patterns of gene expression were observed. Group 1 contained mRNA species encoding P450 side chain cleavage (P450(scc)), P450(c17), relaxin-like factor (RLF), glutathione S-transferase 5-5 (GST5-5), StAR protein, LH receptor, and epoxide hydrolase (EH); group 2 contained 3beta-hydroxysteroid dehydrogenase (3beta-HSD) VI, 17beta-hydroxysteroid dehydrogenase (17beta-HSD) III, vascular cell adhesion molecule 1, estrogen sulfotransferase, and prostaglandin D (PGD)-synthetase; group 3 contained patched and thrombospondin 2 (TSP2); group 4 contained 5alpha-reductase 1 and 3alpha-hydroxysteroid dehydrogenase; group 5 contained sulfonylurea receptor 2 and 3beta-HSD I. Group 1 contained genes that were expressed in fetal and adult Leydig cells and which increased in expression around puberty toward a maximum in the adult. Group 2 contained genes expressed only in the adult Leydig cell population. Group 3 contained genes with predominant fetal/neonatal expression in the interstitial tissue. Group 4 contained genes with a peak of expression around puberty, whereas genes in group 5 show little developmental change in expression. Highest mRNA levels in descending order were RLF, P450(c17), EH, 17beta-HSD III, PGD-synthetase, GST5-5, and P450(scc). Results identify five genes expressed in the mouse adult Leydig cell population, but not in the fetal population, and one gene (TSP2) that may be expressed only in the fetal Leydig cell population. The developmental pattern of gene expression suggests that three distinct phases of adult Leydig cell differentiation occur.

17-Hydroxysteroid Dehydrogenases↗

PubMed2001

E. coli nitroreductase/CB1954: in vitro studies into a potential system for feline cancer gene therapy.

Investigations were carried out to identify a suitable prodrug activating system for feline gene therapy with the eventual aim of treating feline thyroid disease and feline neoplasia. The E. coli nitroreductase (NTR)/CB1954 prodrug activating system was evaluated in vitro in feline cells by transient transfection with a nitroreductase expressing construct and subsequent treatment with the prodrug CB1954. The feline cells successfully expressed E. coli nitroreductase, which was able to activate the prodrug CB1954 resulting in cytotoxicity to both transformed and adjacent cells (a bystander effect) in vitro. In the absence of nitroreductase, CB1954 was non-toxic to feline cells. In addition, the nitroreductase gene was expressed in rat thyroid cells under the control of the cell type specific feline thyroglobulin promoter. This paper demonstrates that the E. coli nitroreductase/CB1954 system may be suitable for in vivo feline gene therapy, and further investigations are warranted.

Animals↗

PubMed2001

Role of gonadotrophins in regulating numbers of Leydig and Sertoli cells during fetal and postnatal development in mice.

The role of the gonadotrophins in regulating numbers of Leydig and Sertoli cells during fetal and postnatal development was examined using normal mice and hypogonadal (hpg) mice, which lack circulating gonadotrophins. The disector method was used to determine the number of cells from day 16 of gestation until adulthood. The numbers of Leydig cells did not change significantly between day 16 of gestation and day 5 after parturition in normal mice and were not significantly different from numbers in hpg mice at any age up to day 5 after parturition. There was a 16-fold increase in the number of Leydig cells in normal mice between day 5 and day 20 after parturition, followed by a further doubling of number of cells between day 20 and adulthood. The number of Leydig cells in hpg testes did not change between day 5 and day 20 after parturition but doubled between day 20 and adulthood so that the number of cells was about 10% of normal values from day 20 onwards. Leydig cell volume was constant in normal animals from birth up to day 20 and then showed a 2.5-fold increase in adult animals. Leydig cell volume was normal in hpg testes at birth but decreased thereafter and was about 20% of normal volume in adult mice. The number of Sertoli cells increased continuously from day 16 of gestation to day 20 after gestation in normal mice and then remained static until adulthood. The number of Sertoli cells in hpg testes was normal throughout fetal life but was reduced by about 30% on day 1 (day of parturition). Thereafter, Sertoli cells proliferated at a slower rate but over a longer period in the hpg testis so that on day 20 after parturition the number of Sertoli cells was about 50% of normal values, whereas in adult mice the number was 65% of normal. The number of gonocytes did not change between day 16 of gestation and day 1 and did not differ between normal and hpg testes. The number of gonocytes increased nine-fold in normal testes but only three-fold in hpg testes between day 1 and day 5 after parturition. Gonocytes differentiated into spermatogonia in both normal and hpg testes between day 5 and day 20 after parturition. These results show: (i) that fetal development of both Sertoli and Leydig cells is independent of gonadotrophins; (ii) that normal differentiation and proliferation of the adult Leydig cell population (starting about day 10 after parturition) is dependent on the presence of gonadotrophins; and (iii) that the number of Sertoli cells after birth is regulated by gonadotrophins, although proliferation will continue, at a lower rate and for longer, in the absence of gonadotrophins.

Animals↗

PubMed2001

Expression of prostaglandin D synthetase during development in the mouse testis.

Prostaglandin D synthetase is expressed relatively highly in the testis and reproductive tract of a number of species, including the mouse. In adult mouse testis, expression is confined largely to the Leydig cells and in this study changes in the expression and localization of prostaglandin D synthetase mRNA during testis development were examined. Initial studies using RT-PCR and isolated testicular compartments indicated that prostaglandin D synthetase expression in the neonatal testis was predominantly within the seminiferous tubules. In situ hybridization studies confirmed that prostaglandin D synthetase mRNA appears to be expressed only in the tubules of neonatal mouse testes and only in the interstitial tissue of the adult testis. TaqMan real-time PCR was used to quantify prostaglandin D synthetase mRNA content during development using an exogenous mRNA as a control standard. Expression per testis decreased after birth to < 10% at day 15 before recovering again by days 25-30. After day 30, expression per testis increased 40-fold during final development to adulthood. Studies using RT-PCR showed that early expression before day 15 was restricted to the tubular compartment, whereas the subsequent increase in expression after day 30 was restricted to the interstitial compartment. Database analysis showed that the 3' end of the prostaglandin D synthetase transcript was subject to alternate splicing. Both splice isoforms were shown by RT-PCR to be present throughout development and without a major change in expression pattern. These results indicate that expression of prostaglandin D synthetase mRNA shifts during development from the tubular compartment of the fetal or neonatal testis to the developing adult Leydig cells, with expression in the Leydig cells increasing markedly after puberty. These changes are similar to those observed for 17beta-hydroxysteroid dehydrogenase type III and may indicate that this developmental process is not uncommon in the testis.

Alternative Splicing↗

PubMed2001

Ovarian function and FSH receptor characteristics during canine anoestrus.

Ovaries of bitches are relatively inactive during anoestrus despite apparently adequate circulating FSH concentrations. Alternative FSH receptor (FSH-R) transcripts in bitches might hinder the follicular response to gonadotrophins, which may account for anoestrus. The expression of the full length FSH-R and novel isoforms in bitches was examined using in situ hybridization and RT-PCR analysis. Various PCR primers to the FSH-R were used and its expression was assessed in ovarian tissue at different stages of the oestrous cycle. RT-PCR amplification of the extracellular domain (exon 1-10) was generally successful, indicating that cFSH-R expression (> 90%) occurs throughout the oestrous cycle. Two FSH-R isoforms were sequenced, but there were no clear differences in the pattern of expression between anoestrus and other stages of the oestrous cycle, except that isoform expression was less frequent (30% occurrence) in prepubertal bitches. Data from in situ hybridization showed clear expression of the FSH-R in secondary and antral follicles, and corpora lutea. It was concluded that there is no evidence of a change in the expression of the FSH-R specific to anoestrus.

Amino Acid Sequence↗

PubMed2000

Localization of 17beta-hydroxysteroid dehydrogenase/17-ketosteroid reductase isoform expression in the developing mouse testis--androstenedione is the major androgen secreted by fetal/neonatal leydig cells.

The final step in the biosynthesis of testosterone is reduction of androstenedione by the enzyme 17beta-hydroxysteroid dehydrogenase/ 17-ketosteroid reductase (17betaHSD/17KSR). In this study, we have examined expression of the four known reductive isoforms of 17betaHSD/ 17KSR (types 1, 3, 5, and 7) in the developing mouse testis and have determined changes in the localization of isoform expression and testosterone secretion during development. Using RT-PCR isoforms 1, 3, and 7 were shown to be expressed in the seminiferous tubules of neonatal testis, whereas isoforms 3 and 7 were expressed in the interstitial tissue of the adult testis. The type 7 isoform is unlikely to be involved in androgen synthesis and further study concentrated on the type 3 isoform. Developmentally, isoform type 3 was expressed in the seminiferous tubules up to day 10, showed little or no expression on day 20 and from day 30 was confined to the interstitial tissue. In situ hybridization confirmed that the type 3 isoform was expressed only in the seminiferous tubules in fetal testes and in the interstitial tissue in adult testes. In accordance with the localization of enzyme messenger RNA expression 17-ketosteroid reductase enzyme activity was very low in isolated interstitial tissue from neonatal testes while interstitial tissue from adult testes showed high activity. Seminiferous tubules from both neonatal and adult testes showed high levels of enzyme activity. The major androgen secreted by the interstitial tissue of prepubertal animals was androstenedione up to day 20 while 5alpha-androstanediol and/or testosterone were the major androgens secreted from day 30 onwards. These results show that fetal Leydig cells do not express significant levels of a reductive isoform of 17betaHSD/ 17KSR and that androstenedione is the major androgen secreted by these cells. Production of testosterone up until puberty is dependent upon 17betaHSD/17KSR activity in the seminiferous tubules--a "two cell" requirement for testosterone synthesis. Expression of the 17betaHSD/17KSR type 3 isoform (the main reductive isoform in the testis) declines in the seminiferous tubules before puberty but then reappears in the developing adult Leydig cell population.

17-Hydroxysteroid Dehydrogenases↗

PubMed2000

Formation of a secondary corpus luteum after ultrasound-guided follicular aspiration in cows.

This paper reports the observed formation of a secondary corpus luteum (CL) in the presence of the cyclic corpus luteum, on the ovaries of a cow after ultrasound-guided follicular aspiration for oocyte recovery. The secondary structure, although smaller and lighter (4.97 g vs. 6.02 g) than the natural one, had the typical macroscopic appearance of a corpus luteum. Histological examination of the structure using electron microscopy revealed typical structural features of a natural CL. Mean tissue progesterone concentration was significantly lower in the secondary CL (31.15 +/- 3.11 compared with 58.29 +/- 6.32 micrograms/g tissue of the cyclic CL) and oestradiol-17 beta significantly higher than in the natural CL (108 +/- 11.6 compared with 74.2 +/- 7.81 pg/g tissue). P450scc and P450(17 alpha) mRNA was detected in both structures while P450arom and full-length mRNA FSH receptor were detected only in the secondary structure.

Animals↗

PubMed1999

Plasma estradiol FSH and LH concentration after dominant follicle aspiration in the cow.

This work investigates the estrogenic role of the dominant follicle with regard to regulation of plasma FSH and LH concentration. Eight Holstein-Friesian cows were used for aspiration of the dominant follicle using ultrasound guidance during the early, mid and late stages of the luteal phase. Blood samples were collected at 15-min intervals from 4 h before until 7 h after aspiration. Plasma progesterone concentration increased from 0.7 to 7.2 ng mL-1 from early to mid luteal phase and then fell slightly to 5.9 ng mL-1 in the late luteal phase, but remained unaffected by follicle puncture. The follicular aspirate contained a thousandfold higher estradiol, than plasma concentration but its estradiol:progesterone ratio remained at around 2 at each stage of the luteal phase. Aspiration caused plasma estradiol concentration to fall from 1.4 to 0.7, 1.8 to 1.0 and 1.7 to 0.8 pg mL-1 in the early, mid and late stages of the luteal phase, respectively (P < 0.05). At the same time, mean plasma FSH concentration was increased from 1.1 to 1.8, 1.7 to 2.9 and 0.8 to 1.9 ng mL-1 (P < 0.05), respectively. The results suggest that estradiol secreted from dominant follicles selectively regulates gonadotropin secretion, since aspiration of the dominant follicle at any stage of the cycle affected circulating FSH but did not appear to influence the mean LH concentration.

Animals↗

PubMed1999

Expression of 3beta-hydroxysteroid dehydrogenase type I and type VI isoforms in the mouse testis during development.

Six isoforms of the enzyme 3beta-hydroxysteroid dehydrogenase (3betaHSD) have been identified in the mouse, each the product of a distinct gene. Two of these isoforms (type I and type VI) are detectable in the adult testis but changes in their expression during development are unknown. In this study we have examined changes in testicular expression and localization of mRNA encoding the type I and type VI isoforms of 3betaHSD. Total 3betaHSD (type I plus type VI) mRNA was measured by reverse transcription-polymerase chain reaction and showed a peak of expression at day 5 after birth followed by a decline and then a further rise after day 10 that continued up to adulthood. When each isoform was measured individually it was clear that the type I isoform was expressed at all ages from embryonic day 13 to adulthood. In contrast, the type VI isoform was only expressed at significant levels during fetal life on embryonic day 13 and then not again until after day 10 postnatally. Expression of the type VI isoform mRNA increased markedly after day 10 so that by adulthood it was the predominant 3betaHSD isoform present in the testis. Closer examination of the timing of type VI expression showed that the isoform mRNA was first detectable at a significant level on day 11. In-situ hybridization confirmed that the type I isoform is the only one expressed in the fetal/neonatal animal and showed that expression was limited to the interstitial tissue. In the adult, both type I and type VI expression was within the interstitial tissue. The timing of 3betaHSD type VI mRNA expression suggests, strongly, that this isoform is expressed only by adult-type Leydig cells in the mouse testis and that this development starts shortly before day 11. The limited expression of the type VI isoform means that it will be a useful marker in studies of adult Leydig cell development.

3-Hydroxysteroid Dehydrogenases↗

PubMed1998

Fetal development of Leydig cell activity in the mouse is independent of pituitary gonadotroph function.

During fetal development the testes secrete anti-Mullerian hormone and testosterone to induce formation of the male phenotype. Adult Leydig cells secrete testosterone under the control of LH, but the role of the fetal pituitary in regulating fetal Leydig cell function is unclear. To study the early relationship between pituitary and Leydig cell function, we have examined the development of fetal pituitary LH levels and Leydig cell function in normal mice and in hypogonadal (hpg) mice that lack GnRH and, thus, circulating gonadotropins. In normal and hpg mice, pituitary LH content was barely detectable until embryonic day 17 (E17), when levels began to increase significantly in both groups. Pituitary levels of LH in hpg mice were, however, only about 10% of normal at all ages. Full-length LH receptor transcripts were first detectable in fetal testes on E16 in both normal and hpg mice. In normal mice, levels of testicular messenger RNA (mRNA) encoding cytochrome P450 side-chain cleavage and 17alpha-hydroxylase increased from E13 to reach a peak around birth. In hpg mice, levels of mRNA encoding these enzymes were normal until around birth, at which time there was a significant decline. Levels of testicular mRNA encoding 3beta-hydroxysteroid dehydrogenase type I were similar in normal and hpg mice and showed little change during development. Intratesticular testosterone reached a peak on E18 in normal animals before declining again after birth. In hpg mice, intratesticular testosterone levels were normal throughout fetal development and on the day of birth, but were barely detectable by postnatal day 5. Results show 1) that fetal Leydig cell function in the mouse is normal in the absence of endogenous circulating gonadotropins; 2) that Leydig cells become dependent on gonadotropins shortly after birth; and 3) that pituitary LH synthesis can start in the absence of GnRH but is dependent on LH for a normal level of synthesis and secretion.

Animals↗

PubMed1997

Use of the polymerase chain reaction to sex the bovine fetus using cells recovered by ultrasound-guided fetal fluid aspiration.

The aim of this study was to carry out first trimester fetal sex diagnosis using the polymerase chain reaction (PCR) to amplify DNA from bovine fetal cells recovered by transvaginal ultrasound-guided uterine puncture and fetal fluid aspiration. For sex determination, a nested, allele-specific, PCR amplification of the bovine zfx and zfy gene fragments was utilised. The PCR assay was validated using fetal fluids recovered from uteri post mortem. Cells were harvested from the fetal fluids, genomic DNA extracted and the PCR assay applied. A technique which was developed for transvaginal ultrasound-guided follicle aspiration was modified to recover fetal fluid from live animals. Small volumes of fetal fluid (0.5-5 ml) were recovered between days 61-97 of gestation and the PCR assay applied. The gender determined by PCR of fetal fluid cells was in all cases confirmed by visual inspection (n = 15 abattoir specimens) or ultrasound scanning (n = 7 live animals). Fetal death, attributed to the introduction of intrauterine infection, occurred in 4/4 cows in the first series of aspirations but in only 1/3 heifers in the second series of aspirations.

Abattoirs↗

PubMed1997

Sequence of the bovine HDL-receptor (SR-BI) cDNA and changes in receptor mRNA expression during granulosa cell luteinization in vivo and in vitro.

Steroidogenic activity in the mature corpus luteum of most mammals depends upon provision of cholesterol from the circulating lipoproteins. In cattle, as in many species, high-density lipoprotein (HDL) is the major lipoprotein involved. The recent identification of the scavenger receptor SR-BI as an HDL-receptor allows control of this process to be investigated more closely. In this study, we have sequenced the bovine SR-BI HDL-receptor and examined changes in expression of the receptor mRNA during corpus luteum development in vivo and granulosa cell luteinization in vitro. Sequencing of the bovine HDL-receptor showed that it codes for a protein of 509 amino acids with close identity to hamster, mouse, rat and human sequences. Examination of the tissue distribution of the HDL-receptor mRNA showed high levels in adrenal cortex and corpus luteum and lower levels in spleen and liver. Using a semi-quantitative, reverse transcription-polymerase chain reaction technique levels of HDL-receptor mRNA were measured in corpora lutea from cattle at known stages of the oestrus cycle and in bovine granulosa cells luteinized in culture. Levels of HDL-receptor mRNA were low in isolated bovine granulosa cells, but increased 7-fold during corpus luteum development in vivo and 5-fold during granulosa cell luteinization in culture. Results show that luteinization of granulosa cells is associated with an increase in HDL-receptor RNA levels which, along with changes in steroidogenic enzyme activity, is likely to explain the marked increase in steroidogenic capacity which occurs during corpus luteum formation.

Amino Acid Sequence↗