Hormonal regulation of mammary differentiation and milk secretion

The endocrine system coordinates development of the mammary gland with reproductive development and the demand of the offspring for milk. Three categories of hormones are involved. The levels of the reproductive hormones, estrogen, progesterone, placental lactogen, prolactin, and oxytocin, change during reproductive development or function and act directly on the mammary gland to bring about developmental changes or coordinate milk delivery to the offspring. Metabolic hormones, whose main role is to regulate metabolic responses to nutrient intake or stress, often have direct effects on the mammary gland as well. The important hormones in this regard are growth hormone, corticosteroids, thyroid hormone, and insulin. A third category of hormones has recently been recognized, mammary hormones. It currently includes growth hormone, prolactin, PTHrP, and leptin. Because a full-term pregnancy in early life is associated with a reduction in breast carcinogenesis, an understanding of the mechanisms by which these hormones bring about secretory differentiation may offer clues to the prevention of breast cancer.     

Physiology of the pituitary, thyroid and adrenal glands

The pituitary gland is made of clusters of cells producing specific hormones that control growth (growth hormones, GH), thyroid function (TH), adrenal function (ACTH), gonadal function (FSH and LH). In addition, the neurons that join the posterior pituitary (neurohypophysis) secrete vasopressin - the antidiuretic hormone involved in maintaining water balance.The negative feedback loop is the basic mechanism to control the regulation of all endocrine glands. Hypothalamic peptides - releasing hormones (e.g. TRH, CRH) reach the hypophysis via the portal venous system and induce the secretion of specific stimulating hormones (e.g. TSH, ACTH) that drive the end-target endocrine cells to secrete hormones (e.g. thyroid hormones - T3 and T4 or adrenal hormones - cortisol, DHEAS). The plasma levels of these circulating hormones inhibit the pituitary (short feedback) or the hypothalamus (long feedback) and limit the further release of releasing- and stimulating- hormones.The effects of circulating hormones on different tissues are mediated via specific receptors on the cell membrane (e.g. vasopressin receptors), in the cytoplasm (steroid receptor for cortisol) or in the nucleus (e.g. thyroid hormone receptors). Understanding the physiological effects of peripheral hormones helps understanding the mechanisms by which clinical signs and symptoms developed in diseases characterised by excessive hormone secretion (e.g. thyrotoxicosis, Cushing syndrome, phaeochromocytomas) or lack of hormone secretion (e.g. diabetes insipidus).     

Elevated Fibroblast Growth Factor 23 Exerts Its Effects on Placenta and Regulates Vitamin D Metabolism in Pregnancy of Hyp Mice

Fibroblast growth factor 23 (FGF23) functions in an endocrine fashion and requires α‐Klotho to exert its effects on the target organs. We have recently demonstrated that the human placenta also expresses α‐Klotho, which led us to hypothesize that FGF23 may exert effects on the placenta. Immunohistochemical analysis demonstrated the expression of FGF receptor 1 (FGFR1) as well as that of α‐Klotho in the feto‐maternal interface of both mouse and human normal‐term placentas, which suggested that these areas might be receptive to FGF23. Therefore, we next investigated whether FGF23 has some roles in the placenta using Hyp mice with high levels of circulating FGF23. Hyp and wild‐type (WT) females were mated with WT males, and the mothers and their male fetuses were analyzed. FGF23 levels in Hyp mothers were elevated. FGF23 levels were about 20‐fold higher in Hyp fetuses than in Hyp mothers, whereas WT fetuses from Hyp mothers exhibited low levels of FGF23, as did fetuses from WT mothers. We analyzed the placental gene expression and found that the expression of Cyp24a1 encoding 25OHD‐24‐hydroxylase, a target gene for FGF23 in the kidney, was increased in the placentas of fetuses from Hyp mothers compared with fetuses from WT mothers. In an organ culture of WT placentas, treatment with plasma from Hyp mothers markedly increased the expression of Cyp24a1, which was abolished by the simultaneous addition of anti‐FGF23 neutralizing antibody. The direct injection of recombinant FGF23 into WT placentas induced the expression of Cyp24a1. The increase in the placental expression of Cyp24a1 in fetuses from Hyp mothers resulted in decreased plasma 25‐hydroxyvitamin D levels. These results suggest that increased levels of circulating FGF23 in pathological conditions such as Hyp mice exerts direct effects on the placenta and affects fetal vitamin D metabolism via the regulation of Cyp24a1 expression. © 2014 American Society for Bone and Mineral Research.     

Placental growth factor and placental protein 13 in patients with Balkan endemic nephropathy,a worldwide disease

Abstract

Background: Balkan endemic nephropathy (BEN) is a chronic tubulointerstitial kidney disease occurring in people living in along the tributaries of the Danube River. The aim of the study was to determine serum level and urinary excretion of placental growth factor (PlGF) and placental protein 13 (PP13) in patients with BEN. Methods: Thirty patients with BEN from the South Morava River region of Serbia and 18 controls were studied. Age of patients was 74?yr (53–87) and 73?yr (66–83) in controls. Results: In patients with BEN, serum creatinine was significantly higher than in controls (129.7 vs. 83.2?µmol/L, respectively), but GFR was lower in patients than in controls (40.7 vs. 54.6?mL/min). Serum PlGF was significantly higher in BEN patients than in controls (9.90 vs. 6.80?pg/mL), urinary excretion being significantly lower in patients (0.20 vs. 0.90?pg/mmol creat.). Serum PP13 was significantly lower in BEN patients (208.2 vs. 291.0?pg/mL). Urinary excretion of PP13 was also significantly lower in BEN patients than in controls (32.5 vs. 182.5?pg/mmol creat). In multivariate regression analysis BEN, sex and age were significant determinants of the observed changes in PlGF and PP13. Conclusion: Important changes of PlGF and PP13 in patients with BEN were demonstrated, where kidney disease, female sex, and the age have been significant determinants.     

Effects of Catecholamines In Vitro on Lipogenesis in Cultured Adipose Tissue from Young Goats

Freshly prepared and cultured perirenal and omental adipose tissue explants were used to investigate the effect of age and hormones on lipogenesis in young goats. Perinatal (1–2 days of age) and older (24–32 days of age) male goats were used. Adipose explants were cultured (24 h) in the presence of insulin, cortisol and recombinant bovine growth hormone (bST) and subsequently incubated (2 h) in a glucose-free buffer containing (¹⁴C)-acetate in the presence or absence of noradrenaline (Ne) and isoprenaline (Iso) to measure tissue lipogenic responses to hormones added to the culture medium and to measure the responsiveness to catecholamines. Inclusion of hormones in the culture medium did not change lipogenesis during subsequent acute incubation in glucose-free buffer in both perirenal and omental adipose tissue from perinatal goats. On the other hand, in perirenal explants from older animals, insulin alone or insulin plus cortisol increased (P < 0.05) and cortisol alone decreased (P < 0.05) the rate of fatty acid synthesis. When perirenal explants were cultured in the presence of insulin plus cortisol plus bST, the rates of lipogeneses were lower (P < 0.05) than those in cultures with insulin plus cortisol. A similar pattern of the effects of hormones on the rates of fatty acid synthesis was also seen in omental explants; however, these effects were not significant. In vitro rates of lipogeneses were decreased (P < 0.05) by Ne but not Iso in freshly prepared omental explants of both perinatal and older animals and in freshly prepared perirenal explants of older animals. In cultured perirenal explants of both perinatal and older animals the mean values of lipogenesis were decreased (P < 0.05) by both Ne and Iso. However, in cultured omental explants both catecholamines were effective (P < 0.05) in older but not in perinatal animals.     

Angiogenesis and myogenesis in mouse tibialis anterior muscles during distraction osteogenesis: VEGF,its receptors,and myogenin genes expression

Angiogenesis and myogenesis occur in the surrounding skeletal muscles following distraction osteogenesis, but their molecular mechanisms remain unclear. The present study investigated morphological features of lengthened muscles and the time course change of vascular endothelial growth factor (VEGF), its receptors (VEGFR‐1 and VEGFR‐2) and myogenin gene expression profiles related to angiogenesis and myogenesis in tibialis anterior (TA) muscles with a mouse model of distraction osteogenesis, which involves 1 week of waiting period (latency phase), 2 weeks of intermittent distraction (distraction phase), and 5 weeks of remodeling period (consolidation phase). Macroscopic findings showed that lengthened TA muscles increased to approximately 42% longer and 10% heavier at the end of the process when compared to pre‐surgery. During the distraction phase, VEGF and its receptors were induced in the vascular endothelial cells, myogenin‐positive satellite cells and myocytes, and subsequently, capillary progression and myogenesis were increased. Real‐time RT‐PCR showed that Vegf, Vegfr‐1, Vegfr‐2, and myogenin genes expression was enhanced during the muscle lengthening. Vegf and Vegfr‐1 were upregulated following the recession of angiogenesis at the consolidation phase. We conclude that upregulation of VEGF and its receptors by mechanical tension‐stress could be involved in the process of angiogenesis and myogenesis in lengthened muscles. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1767–1773, 2012     

A N-Terminus Domain Determines Amelogenin's Stability to Guide the Development of Mouse Enamel Matrix

Amelogenins, the principal proteins in the developing enamel microenvironment, self-assemble into supramolecular structures to govern the remodeling of a proteinaceous organic matrix into longitudinally ordered hydroxyapatite nanocrystal arrays. Extensive in vitro studies using purified native or recombinant proteins have revealed the potential of N-terminal amelogenin on protein self-assembly and its ability to guide the mineral deposition. We have previously identified a 14-aa domain (P2) of N-terminal amelogenin that can self-assemble into amyloid-like fibrils in vitro. Here, we investigated how this domain affects the ability of amelogenin self-assembling and stability of enamel matrix protein scaffolding in an in vivo animal model. Mice harboring mutant amelogenin lacking P2 domain had a hypoplastic, hypomineralized, and aprismatic enamel. In vitro, the mutant recombinant amelogenin without P2 had a reduced tendency to self-assemble and was prone to accelerated hydrolysis by MMP20, the prevailing metalloproteinase in early developing enamel matrix. A reduced amount of amelogenins and a lack of elongated fibrous assemblies in the development enamel matrix of mutant mice were evident compared with that in the wild-type mouse enamel matrix. Our study is the first to demonstrate that a subdomain (P2) at the N-terminus of amelogenin controls amelogenin's assembly into a transient protein scaffold that resists rapid proteolysis during enamel development in an animal model. Understanding the building blocks of fibrous scaffold that guides the longitudinal growth of hydroxyapatites in enamel matrix sheds light on protein-mediated enamel bioengineering. © 2021 American Society for Bone and Mineral Research (ASBMR).     

Role of fibroblast growth factor receptor signaling in kidney development

Fibroblast growth factor receptors (Fgfrs) are expressed in the ureteric bud and metanephric mesenchyme of the developing kidney. Furthermore, in vitro and in vivo studies have shown that exogenous fibroblast growth factors (Fgfs) increase growth and maturation of the metanephric mesenchyme and ureteric bud. Deletion of fgf7, fgf10, and fgfr2IIIb (the receptor isoform that binds Fgf7 and Fgf10) in mice lead to smaller kidneys with fewer collecting ducts and nephrons. Overexpression of a dominant negative receptor isoform in transgenic mice has revealed more striking defects including renal aplasia or severe dysplasia. Moreover, deletion of many fgf ligands and receptors in mice results in early embryonic lethality, making it difficult to determine their roles in kidney development. Recently, conditional targeting approaches revealed that deletion of fgf8 from the metanephric mesenchyme interrupts nephron formation. Furthermore, deletion of fgfr2 from the ureteric bud resulted in both ureteric bud branching and stromal mesenchymal patterning defects. Deletion of both fgfr1 and fgfr2 in the metanephric mesenchyme resulted in renal aplasia, characterized by defects in metanephric mesenchyme formation and initial ureteric bud elongation and branching. Thus, Fgfr signaling is critical for growth and patterning of all renal lineages at early and later stages of kidney development.     

GPR30 deficiency causes increased bone mass,mineralization, and growth plate proliferative activity in male mice

Estrogen regulation of the male skeleton was first clearly demonstrated in patients with aromatase deficiency or a mutation in the ERα gene. Estrogen action on the skeleton is thought to occur mainly through the action of the nuclear receptors ERα and ERβ. Recently, in vitro studies have shown that the G protein–coupled receptor GPR30 is a functional estrogen receptor (ER). GPR30‐deficient mouse models have been generated to study the in vivo function of this protein; however, its in vivo role in the male skeleton remains underexplored. We have characterized size, body composition, and bone mass in adult male Gpr30 knockout (KO) mice and their wild‐type (WT) littermates. Gpr30 KO mice weighed more and had greater nasal‐anal length (p < .001). Both lean mass and percent body fat were increased in the KO mice. Femur length was greater in Gpr30 KO mice, as was whole‐body, spine, and femoral areal bone mineral density (p < .01). Gpr30 KO mice showed increased trabecular bone volume (p < .01) and cortical thickness (p < .001). Mineralized surface was increased in Gpr30 KO mice (p < .05). Bromodeoxyuridine (BrdU) labeling showed greater proliferation in the growth plate of Gpr30 KO mice (p < .05). Under osteogenic culture conditions, Gpr30 KO femoral bone marrow cells produced fewer alkaline phosphatase–positive colonies in early differentiating osteoblast cultures but showed increased mineralized nodule deposition in mature osteoblast cultures. Serum insulin‐like growth factor 1 (IGF‐1) levels were not different. These data suggest that in male mice, GPR30 action contributes to regulation of bone mass, size, and microarchitecture by a mechanism that does not require changes in circulating IGF‐1. © 2011 American Society for Bone and Mineral Research.     

Placental,Lipid, and Glucidic Effects of Mammalian Target of Rapamycin Inhibitors: Impact on Fetal Growth and Metabolic Disorders During Pregnancy After Solid Organ Transplantation

Background

Mammalian target of rapamycin inhibitors (mTORi) are a promising new family of immunosuppressive drugs. No teratogenic effects have been reported to date. Their lipid and glucidic effects should not be underestimated, however, especially during pregnancy. Moreover, mTORi may affect fetal growth by mTOR placental activity.

Objective

Our purpose was to highlight mTORi placental impact and metabolic implications to detect possible maternal or fetal effects and define management guidelines in pregnant women after solid organ transplantation.

Methods

A literature search was performed for articles from the Medline and Pubmed databases with the use of the following keywords: mTOR inhibitors, pregnancy, placental transport, lipid metabolism, glucose metabolism.

Results

mTOR works as a positive regulator of system A, system L, and taurine placental amino acid transporter activity, which are critical for the transport of amino acids to the fetus. Exposing trophoblast cells to rapamycin reduces system L activity; therefore, treatment with rapamycin in human pregnancies could alter fetal growth with intrauterine growth restriction (IUGR). Regarding the metabolic effects mTORi increase lipolysis, impair insulin's antilipolytic effect and reduce lipid storage, which may potentially contribute to dyslipidemia. Chronic rapamycin treatment reduces adipose tissue size and β-cell mass/function, causes hyperlipidemia, severe insulin resistance, and glucose intolerance, and promotes hepatic gluconeogenesis.

Conclusions

The studies on mTORi treatment in transplanted pregnant women have not focused to date on the potential metabolic and placental effects. Selection of women at high risk for metabolic disorders could be needed and consideration of switching to another immunosuppressive drug required if diabetes and abnormal blood lipids have been diagnosed in prepregnancy counseling. It seems to be mandatory to encourage prompt reporting of any additional cases of pregnancy during mTORi exposure to provide a better understanding of the placental effects and safety profile of these immunosuppressive drugs.     

Expression of growth factor receptors,the focal adhesion kinase,and other tyrosine kinases in human soft tissue tumors

Background: The tyrosine kinases are a family of genes that includes many growth factor receptors and protooncogenes. They appear to have a role in many cancers, but have not been systematically studied in the pathogenesis and progression of human sarcomas. Methods: To characterize the protein tyrosine kinases that are expressed in human sarcomas, we used a polymerase chain reaction (PCR)-based method to construct kinase-specific cDNA libraries from low-grade and high-grade primary tumors. Thereafter, individual tyrosine kinase gene expression was assessed in a panel of sarcoma cell lines and primary tumors using Northern blotting and PCR. Results: We identified 19 species of tyrosine kinase genes, including many growth factor receptors, the human homolog of the focal adhesion kinase (FAK) gene, and a noveltrk-related kinase designated HGK2. Messenger RNA expression analyses showed relative overexpression of the two forms of the platelet-derived growth factor receptors (PDGFRs) with expression of the form restricted to a subgroup of high-grade and metastatic sarcomas. We were unable to demonstrate coexpression of the PDGF isoforms in primary tumors that overexpressed the receptors, suggesting that a PDGF/PDGFR autocrine pathway may not be a central mechanism in the malignant transformation of sarcomas in vivo. FAK expression was observed in a variety of sarcomas, with increased levels in several high-grade and metastatic leiomyosarcomas. Conclusions: When grouped together by histologic cell type and grade, the expression data of the 19 kinases in primary tumors described a greater degree of heterogeneity than is generally appreciated by clinicopathologic classification schemes. This diversity suggests that sarcomas, even those that appear to be clinically similar, arise through a variety of molecular pathways involving tyrosine kinases.Presented at the 46th Annual Cancer Symposium of the Society of Surgical Oncology, Los Angeles, March 18–21, 1993.     

Placental Structure in Type 1 Diabetes: Relation to Fetal Insulin, Leptin, and IGF-I

OBJECTIVE

Alteration of placental structure may influence fetal overgrowth and complications of maternal diabetes. We examined the placenta in a cohort of offspring of mothers with type 1 diabetes (OT1DM) to assess structural changes and determine whether these were related to maternal A1C, fetal hematocrit, fetal hormonal, or metabolic axes.

RESEARCH DESIGN AND METHODS

Placental samples were analyzed using stereological techniques to quantify volumes and surface areas of key placental components in 88 OT1DM and 39 control subjects, and results related to maternal A1C and umbilical cord analytes (insulin, leptin, adiponectin, IGF-I, hematocrit, lipids, C-reactive protein, and interleukin-6).

RESULTS

Intervillous space volume was increased in OT1DM (OT1DM 250 ± 81 cm³ vs. control 217 ± 65 cm³; P = 0.02) with anisomorphic growth of villi (P = 0.025). The placentas showed a trend to increased weight (OT1DM 690 ± 19 g; control 641 ± 22 g; P = 0.08), but villous, nonparenchymal, trophoblast, and capillary volumes did not differ. Villous surface area, capillary surface area, membrane thickness, and calculated morphometric diffusing capacity were also similar in type 1 diabetic and control subjects. A1C at 26–34 weeks associated with birth weight (r = 0.27, P = 0.03), placental weight (r = 0.41, P = 0.0009), and intervillous space volume (r = 0.38, P = 0.0024). In multivariate analysis of cord parameters in OT1DM, fetal IGF-I emerged as a significant correlate of most components (intervillous space, villous, trophoblast, and capillary volumes, all P < 0.01). By contrast, fetal insulin was only independently associated with capillary surface area (positive, r² = 6.7%; P = 0.02).

CONCLUSIONS

There are minimal placental structural differences between OT1DM and control subjects. Fetal IGF-I but not fetal insulin emerges as a key correlate of placental substructural volumes, thereby facilitating feedback to the placenta regarding fetal metabolic demand.Maternal diabetes is associated with adverse consequences to mother and baby, with increased risks of perinatal morbidity and mortality, in particular in association with fetal macrosomia. The Pedersen hypothesis (1) proposed that maternal hyperglycemia drives increased transplacental glucose transfer and thereby compensatory fetal hyperinsulinemia and induction of fetal growth. Although the fetal consequences of maternal glycemia are clearly recognized, there is still uncertainty about the role of the placenta in determining these outcomes. Specifically, the nature and scale of attendant structural change within the type 1 diabetic placenta remains contentious. Notably, the respective contribution of placental structural differences and how these relate to fetal hormonal axes in the attainment of enhanced placental and fetal growth is also unknown, even in control populations.Classically, older histological studies of type 1 diabetic placentas have described grossly abnormal placentas that are enlarged, thick, and plethoric, with abnormalities of villous maturation (2). These changes would all support the increased incidence of placental-related complications observed in diabetic pregnancy (3). However, other historical series have not detected significant differences (2), and more recent stereological studies continue to differ with either no disparity in placental composition (4,5) or isolated changes including increases in capillary volume and surface area (6,7), increased villous surface area (8), increased total diffusive conductance (9), and increased intervillous and trophoblast volume (7,10). This lack of consistency may reflect a combination of small series, grouping of different classes of maternal diabetes, differences in glycemic control between individual patients, recent improvements in antenatal care, and differing methodology.To date, studies in diabetes have also largely used fetal macrosomia as a surrogate of maternal glycemia and excessive transplacental glucose transfer (7,10) rather than assessment of the fetal hormonal response including hyperinsulinemia. Certainly, fetal hyperinsulinemia has an independent positive association with birth weight and placental weight in offspring of mothers with type 1 diabetes (OT1DM) (11). IGF-I and IGF-II also influence feto-placental growth. IGF-I has strong correlations to both birth weight and placental weight in control subjects and OT1DM (11–13). The role of IGF-II is less clear in human studies and is likely modified by circulating IGF-II receptor (12). Adiponectin, although not directly associated with birth weight, does correlate with placental weight and contributes to the matching of fetal and placental growth in control subjects and OT1DM (11,14). Finally, leptin also correlates with placental weight in control subjects and OT1DM and has recently been proposed as an in utero signal of nutrient availability (11,15). Collectively, these fetal hormone axes may therefore facilitate enhanced growth of the fetus and compensatory changes within the placenta, including structural modification, particularly in response to an excessive glucose supply as seen in diabetic pregnancy. To address this potential interaction of maternal environment, fetal hormones, and placental structure, we have examined placentas in relation to birth weight, neonatal adiposity, and fetal hormonal indexes, in particular those of insulin and IGF-I in OT1DM.     

Regional mitogenic response of the meniscus to platelet-derived growth factor (PDGF-AB)

Since meniscal healing is region-specific, we studied the regional (peripheral compared with central) response of meniscal explants to human, recombinant platelet-derived growth factor-AB. Mensical explants from the hindlimbs of both knees of mature sheep were sectioned and were cultured with variable doses of human, recombinant platelet-derived growth factor-AB, and incorporation of [³H]-thymidine was measured. The mitogenic response was measured at different times in culture (48 or 96 hours) and by location (lateral or medial). In the absence of the growth factor, the peripheral third of both menisci incorporated 10-fold more [³H]-thymidine on a weight basis than did the central two-thirds. Cellularity was equivalent in the two regions. Doses of less than 100 ng/ml of growth factor produced either no stimulation or a variable response. A dose of 100 ng/ml resulted in consistent, significant (p < 0.05) stimulation in all groups in the peripheral region, and a dose of 200 ng/ml provided more than a 2.5-fold increase. Multiple-factor analysis of variance demonstrated that there were no significant differences between experiments, times in culture, or menisci. The central region did not respond to stimulation with the growth factor at any of the doses tested. These data suggest that regional differences (peripheral compared with central) in responsiveness to human, recombinant platelet-derived growth factor-AB may reflect a different level of signal transduction machinery for growth factor receptors and distinct fibrochondrocyte populations. These findings are consistent with the variable healing capcity of the meniscal regions in vivo and suggest a pharmacological means to promote the repair of the peripheral meniscal region.     

Immunohistochemical Analysis of Vascular Endothelial Growth Factor and Hepatocyte Growth Factor,and Their Receptors,in Transplanted Islets in Rats

Purpose. Our previous studies showed that transplanted islets increasingly express a marker of neovascularization, platelet endothelial cell adhesion molecule-1 (PECAM-1), as well as vascular endothelial growth factor (VEGF). Hepatocyte growth factor (HGF) is another stimulator of neovascularization. In this study, we examined the expression of these growth factors and their receptors; fetal liver kinase-1 (Flk-1) for VEGF and c-Met for HGF, to acertain whether VEGF and HGF play a role in the neovascularization of transplanted islets. Methods. Islets were isolated from male Lewis rats by collagenase digestion and the discontinuous dextran gradient method, then transplanted into the bilateral subnephrocapsular space. The kidneys were excised 1–28 days after transplantation, then fixed in formaldehyde and embedded in paraffin. Serial slices were immunostained for VEGF, HGF, Flk-1, or c-Met, respectively. Results. Islets in the normal pancreas were positively stained for VEGF, HGF, and c-Met; however, Flk-1 was only stained at the periphery of the islets. In the transplanted islets, staining for VEGF, HGF, and c-Met was positive, but Flk-1 was not stained. Moreover, staining for HGF and c-Met became stronger in the transplanted islets with time. Conclusion. These results suggest that HGF, rather than VEGF, may play a role in the neovascularization of transplanted islets.     

Effect of Testosterone and Oestradiol‐17β on Canine Hair Follicle Culture

Skin biopsies were taken from four body sites (head, thorax, flank and perineum) of three male entire Beagles and the primary hair follicles were isolated. Culture conditions were established to keep the hair follicles growing for up to 7 days. Additionally, hair follicles were incubated in supplemented medium (containing insulin, transferrin, glutamine and sodium selenite) with or without the addition of testosterone (T) (1, 10 or 100 ng/ml) or oestradiol‐17β (E2β) (0.01, 0.1 or 1 ng/ml), respectively and the daily growth of hair follicles was measured. In vitro daily growth of hair follicles from the thorax was stimulated by the low concentration of both hormones, but the growth of those from the flank was inhibited by the high concentration of both hormones. Hair follicles from the head were positively influenced by the lowest concentration of T and the medium concentration of E2β. The daily growth of hair follicles from the perineum was not significantly influenced by either hormone.