Biomedical subjects

Giovanna Albertin

Publications and source records attributed to Giovanna Albertin.

At least 19 recordsLinked to original sources

PubMed2006

Age-dependent decrease in the ghrelin gene expression in the human adrenal cortex: a real-time PCR study.

Numerous lines of evidence indicate that ghrelin, an endogenous ligand of the growth hormone-secretagogue receptor, is expressed in the human and rat adrenal cortex. In this study, we examined whether ghrelin gene expression undergoes changes in the human adrenal cortex during aging. Semi-quantitative real-time reverse transcription-polymerase chain reaction demonstrated a highly significant negative correlation between ghrelin mRNA and age in adrenal cortex of 27 patients (aged from 33 to 82 years), who underwent unilateral adrenalectomy/nephrectomy for kidney cancer. No significant differences in the level of adrenal ghrelin expression were observed between males and females. Since it has been previously shown that ghrelin exerts a marked growth-stimulating action on cultured adrenocortical cells, we hypothesize that the down-regulation of ghrelin gene transcription in adrenals could be associated with the reported decrease in adrenal DNA synthesis and mitogenic activity during aging.

Adrenal Cortex↗

PubMed2006

In vitro culture on Matrigel favors the long-term maintenance of rat zona glomerulosa-cell differentiated phenotype.

Zona glomerulosa (ZG) cells cultured on plastic within few days dedifferentiate losing their capacity to secrete aldosterone (ALDO) in appreciable amounts. Evidence indicates that extracellular matrix modulates the secretory behavior of adrenocortical cells cultured in vitro. Hence, we compared the morphology and function of rat ZG cells grown on plastic and Matrigel basement membrane matrix (hereinafter Matrigel) for up to 12 days. At day 3, no significant differences were observed between cells cultured on plastic and Matrigel. Starting from day 6, ZG cells cultured on plastic lost their ultrastructural differentiated features (mitochondria with tubular cristae, smooth endoplasmic reticulum cisternae and lipid droplets), exhibiting a fibroblast-like appearance. The mRNA expression of the main steroidogenic enzymes, as evaluated by real-time polymerase chain reaction, the baseline secretion of ALDO and other post-pregnenolone hormones, as evaluated by high pressure liquid chromatography, and the secretory response to ACTH, angiotensin-II and K(+), as evaluated by radioimmunoassay, displayed a time-dependent decrease. Matrigel was found to maintain unchanged both the ultrastructure and the expresion of steroidogenic enzymes of ZG cells until day 12 of culture. Baseline and agonist-stimulated steroid-hormone secretion decreased with the duration of culture on Matrigel, but was always higher than that of ZG cells grown on plastic. Hence, our study clearly indicates that the culture on Matrigel favors the maintenance of rat ZG-cell differentiated phenotype, allowing the conclusion that this technique is suitable for long-term in vitro investigations.

Adrenocorticotropic Hormone↗

PubMed2006

Urotensin-II and UII-receptor expression and function in the rat adrenal cortex.

Urotensin-II (UII) is a potent hypertensive peptide, which has been recognized as an endogenous ligand of the G protein-coupled receptor (GPR)-14, now named UT-R. Real-time PCR demonstrated the expression of UII and UT-R mRNAs in both dispersed and in vitro cultured rat adrenocortical cells. UII concentration-dependently decreased basal, but not ACTH-stimulated, corticosterone secretion from cultured adrenocortical cells, and the effect was abolished by the UT-R antagonist Palosuran. UII did not affect the proliferation rate of cultured cells. Taken together, these findings suggest that UII may be included in the group of peptides (adrenomedullin, atrial natriuretic peptide, neurotensin and beacon), that, acting in an autocrine-paracrine manner, are involved in the inhibitory tuning of adrenocortical secretion.

Adrenal Cortex↗

PubMed2006

Gene silencing of human RAMP2 mediated by short-interfering RNA.

Adrenomedullin (AM) is a regulatory peptide widely expressed, along its receptors, in cells and tissues, of which it controls many basic and specific functions acting in an autocrine-paracrine manner. However, the unequivocal demonstration of the physiological relevance of the regulatory role of AM would require the study of cells where the endogenous AM system has been suppressed. For this task we developed a technique to silence the AM gene in human umbilical vein endothelial cells (HUVECs) and the human embryonal kidney cell line (HEK-293). AM acts via two subtypes of receptor, named AM1 and AM2, which derive from the interaction of the calcitonin receptor-like receptors with two chaperones, called receptor activity modifying proteins (RAMP2 and RAMP3). Hence, we developed a protocol to suppress the human AM1 receptor by silencing the RAMP2 gene by transfection with short interfering RNAs (siRNAs). HUVECs were transfected using a new Ambion transfection reagent. RAMP2 gene silencing was determined in HUVECs by measuring RAMP2 mRNA levels in transfected and control cells by real-time polymerase chain reaction. The RAMP2 gene silencing was approximately 60% and was observed 48 h after transfection. Matrigel assay in vitro was carried out to evaluate the effects of siRNA sequences. HUVECs cells were plated on matrigel and the analysis of capillary-like tubule formation showed that the cells were viable. The knockdown of the RAMP2 gene decreased the formation of tubes in response to 10(-8) M AM. The conclusion is drawn that siRNA technology can be successfully used in the investigations on AM and AM receptor functions.

Adrenomedullin↗

PubMed2006

Urotensin-II and its receptor (UT-R) are expressed in rat brain endothelial cells, and urotensin-II via UT-R stimulates angiogenesis in vivo and in vitro.

Urotensin-II (UII), along its receptor UT-R, is widely expressed in the cardiovascular system, where it exerts regulatory actions under both physiological and pathological conditions. Real-time PCR and immunocytochemistry demonstrated the expression of UII and UT-R as mRNA and protein in rat neuromicrovascular endothelial cells (NECs). UII did not affect the proliferation rate of cultured NECs, but exerted a strong angiogenic action in both an in vitro assay on Matrigel and an in vivo assay on chorioallantoic membrane. The angiogenic effect of UII was similar to that of FGF-2, and was abolished by the UT-R antagonist Palosuran. Collectively, our findings allow us to include UII in the group of cytokines (e.g. endothelin-1 and adrenomedullin), which are expressed in endothelial cells and exert a pro-angiogenic effect acting in an autocrine-paracrine manner.

Animals↗

PubMed2005

Orexins stimulate glucocorticoid secretion from cultured rat and human adrenocortical cells, exclusively acting via the OX1 receptor.

Orexins A and B are hypothalamic peptides, that act via two subtypes of receptors, named OX1-R and OX2-R. Rat and human adrenal cortexes are provided with both OX1-R and OX2-R, and we have previously shown that orexin-A, but not orexin-B, enhances glucocorticoid secretion from dispersed adrenocortical cells. Since OX1-Rs preferentially bind orexin-A and OX2-Rs are non-selective for both orexins, the hypothesis has been advanced that the secretagogue effect of orexin-A is exclusively mediated by the OX1-R. Here, we aimed to verify this contention and to gain insight into the signaling mechanism(s) underlying the secretagogue effect of orexins using primary cultures of rat and human adrenocortical cells. Reverse transcription-polymerase chain reaction showed that cultured cells, as freshly dispersed cells, expressed both OX1-R and OX2-R mRNAs. Orexin-A, but not orexin-B, concentration-dependently increased corticosterone and cortisol secretion from cultured rat and human adrenocortical cells, respectively. The blockade of OX1-Rs by selective antibodies abrogated the secretagogue effect of orexin-A, while the immuno-blockade of OX2-Rs was ineffective. The glucocorticoid response of cultured cells to orexin-A was annulled by the adenylate cyclase and protein kinase (PK) A inhibitors SQ-22536 and H-89, and unaffected by the phospholipase C and PKC inhibitors U-73122 and calphostin-C. Orexin-A, but not orexin-B, enhanced cyclic-AMP production from cultured cells, and did not alter inositol-3-phosphate release. Collectively, our present results allow us to conclude that orexins stimulate glucocorticoid secretion from rat and human adrenocortical cells, exclusively acting through OX1-Rs coupled to the adenylate cyclase/PKA-dependent signaling cascade.

Adrenal Cortex↗

PubMed2005

Similar sequence-free amplification of human glyceraldehyde-3-phosphate dehydrogenase for real time RT-PCR applications.

One of the major applications of real time polymerase chain reaction (PCR) is relative quantification, where the expression of a target gene is determined as a ratio to a stably expressed reference gene, the so-called housekeeping gene. Glyceraldehyde-3-phosphate dehydrogenase (GAPD) is a glycolytic enzyme, which is active in all mammalian tissues and is frequently used as housekeeping gene in expression studies. The functional locus maps to human chromosome 12p13, but several GAPD-related sequences, including processed pseudogenes, GenBank homologous sequences and computationally predicted sequences are present along the human genome. Due to the high level of GAPD-related sequences it is very important to avoid genomic DNA amplification when GAPD is used as endogenous control in mRNA quantification. We have outlined a GAPD couple of primers that avoid any genomic DNA amplification for real time reverse transcription PCR applications by SYBR-Green Dye. These new designed primers are an useful and chip alternative to probe technologies, and can carry out specific and reproducible data in mRNA expression studies.

Base Sequence↗

PubMed2005

Cerebellin in the rat adrenal gland: gene expression and effects of CER and [des-Ser1]CER on the secretion and growth of cultured adrenocortical cells.

Cerebellin (CER) is a regulatory peptide, originally isolated from rat cerebellum, which derives from the cleavage of precerebellin (Cbln), three types of which (Cbln1-3) have been identified in humans and rats. CER is also expressed in several extra-cerebellar tissues, including adrenal gland, and evidence has been provided that CER exerts a modulatory action on human and rat adrenal gland. Hence, we have investigated the expression of Cbln1-3 mRNAs and CER protein-immunoreactivity (IR) in the various zones of rat adrenal glands, and the effects of CER and its metabolite [des-Ser(1)]CER (des-CER) on the secretion and growth of cultured rat adrenocortical cells. Reverse transcription-polymerase chain reaction showed high and low expression of Cbln2 mRNA in zona glomerulosa (ZG) and zona fasciculata-reticularis, respectively. Cbln1 was not expressed, and Cbln3 mRNA was detected only in ZG. No Cbln expression was found in adrenal medulla. Immunocytochemistry demonstrated the presence of CER-IR exclusively in the adrenal cortex, the reaction being more intense in ZG. As expected, ACTH (10(-8) M) markedly enhanced corticosterone secretion and lowered proliferation rate of cultured adrenocortical cells. CER was ineffective, while des-CER exerted an ACTH-like effect, but only at the lowest concentration (10(-10) M). Taken together, these findings allow us to conclude that CER is expressed in rat adrenal cortex, and to suggest that CER conversion to des-CER by endopeptidases is needed for CER to exert its autocrine-paracrine regulatory functions.

Adrenal Glands↗

PubMed2005

Endothelin-1 and adrenomedullin enhance the growth of human adrenocortical carcinoma-derived SW-13 cell line by stimulating proliferation and inhibiting apoptosis.

The human adrenocortical carcinoma-derived SW-13 cell line is currently used to study the interrelationships occurring between cytokines and growth factors and endothelins (ET) and adrenomedullin (AM). SW-13 cells express either ET-1 and AM or growth factors, and several cytokines stimulate ET-1 and AM release from SW-13 cells. However, neither the morphology and steroid-hormone secretion of SW-13 cells nor the expression of ET and AM receptors and the effects of ET and AM on SW-13 cell growth have been investigated. Electron microscopy showed that SW-13 cells were deprived of the typical organelles involved in steroid-hormone synthesis (i.e. mitochondrial with tubular cristae, smooth endoplasmic reticulum and lipid droplets), their prominent ultrastructural features being rough endoplasmic reticulum cisternae, free ribosomes and mitochondria with laminar cristae. Accordingly, steroid-hormone secretion was very low: no cortisol was produced and only very small amounts of aldosterone and its precursors were released. No appreciable secretory response to physiological concentrations of ACTH was observed. Reverse transcription-polymerase chain reaction showed the expression of pro ET-1 and proAM genes, as well as detected the mRNAs of only the ET- and AM-receptor subtypes, which are currently thought to mediate the growth-promoting action of these peptides: i.e. the ETA and AM2 receptors. In keeping with these observations, both ET-1 and AM markedly stimulated the growth of SW-13 cells, by enhancing the proliferation and lowering the apoptosis rate. Taken together, our findings allow us to conclude that SW-13 cannot be used for investigating the mechanisms involved in the regulation of steroid-hormone secretion, but are a suitable and useful model to study the role of endogenous ET and AM systems in the autocrine-paracrine control of human adrenocortical-cell growth.

Adrenocortical Carcinoma↗

PubMed2005

Human adrenomedullin gene silencing by short interfering RNAs: a preliminary study.

Adrenomedullin (AM) is a regulatory peptide widely expressed, along its receptors, in cells and tissues, of which it controls many basic and specific functions acting in an autocrine-paracrine manner. However, the unequivocal demonstration of the physiological relevance of the regulatory role of AM would require the study of cells where endogenous AM system had been suppressed. Hence, we developed a protocol to silence the human AM gene by transfection with short interfering RNAs (siRNAs). Eight possible AM-siRNA sequences were designed: six siRNAs were synthesized in our laboratory and two were provided by Ambion. As positive control the suppression of the glyceraldehyde-3-phosphate dehydrogenase (GADPH) gene was tested using the Ambion Silencer GADPH siRNA kit. Cultured human embryonal kidney cell line HEK-293 and human umbilical vein endothelial cells (HUVECs) were transfected using either the Qiagen or the Ambion transfection reagent, and transfection visualization, carried out using Cy3-labeled siRNA and examining red fluorescence within the cells, showed that the former reagent was the most efficient. AM-gene silencing was determined in HUVECs by measuring AM mRNA levels in transfected and control cells by real-time polymerase chain reaction. Only Ambion siRNAs were effective, and the best AM-gene silencing (about 80%) was observed 48 or 72 h after transfection with 3 or 6 microg of siRNAs. The conclusion is drawn that siRNA technology can be useful in the investigations on AM functions, but that the complete suppression of the AM-gene transcription is very difficult to obtain.

Adrenomedullin↗

PubMed2005

Adrenomedullin and vascular endothelium growth factor genes are overexpressed in the regenerating rat adrenal cortex, and AM and VEGF reciprocally enhance their mRNA expression in cultured rat adrenocortical cells.

Adrenomedullin (AM) is an endogenous regulatory peptide, which exerts growth promoting and neoangiogenic actions in several normal and neoplastic tissues. Evidence has been provided that AM and the pro-angiogenic peptide vascular endothelium growth factor (VEGF) are expressed in the adrenal gland, and we investigated whether their gene transcription is modified in a model of rapid rat adrenal growth, namely regeneration after enucleation and contralateral adrenalectomy. Real-time polymerase chain reaction (PCR) showed that AM and VEGF mRNAs were significantly increased in regenerating adrenals with respect to the intact adrenocortical tissue of sham-operated control rats. Subsequent studies were carried out on dispersed rat adrenocortical cells cultured in vitro for 72 h. Conventional PCR demonstrated that cultured cells expressed AM and VEGF mRNAs. Moreover, real-time PCR showed that 24 h exposure to 10-8 M AM or 50 ng/ml VEGF significantly raised the expression of VEGF and AM, respectively, without affecting that of their own mRNA, suggesting the occurence of autocrine-paracrine up-regulatory mechanisms. Taken together, our findings allow us to conceive that the coordinate up-regulation of AM and VEGF expression may favor cell proliferation and neoangiogenesis, thereby leading to a rapid restoration of morphology and function of regenerating adrenals.

Adrenal Cortex↗

PubMed2004

Growth hormone secretagogue receptor subtypes 1a and 1b are expressed in the human adrenal cortex.

Ghrelin is an endogenous ligand of the growth hormone secretagogue receptors (GHS-Rs), two subtypes of which have been recognized: the biologically active 1a and the biologically inactive 1b subtype. Reverse transcription-polymerase chain reaction demonstrated ghrelin and GHS-R1b mRNAs in eight human adrenal cortexes, and GHS-R1a mRNA only in six of the eight adrenal specimens. The GHS-R1a expression was absent in the two adrenal cortexes obtained from 76- and 79-year old male patients. Since previous studies showed that ghrelin does not affect steroid-hormone secretion, the present findings suggest that ghrelin via the GHS-R1a could be involved in the autocrine-paracrine control of human-adrenal growth.

Adrenal Cortex↗

PubMed2004

Effects of neuropeptides B and W on the secretion and growth of rat adrenocortical cells.

Neuropeptide-B (NPB) and neuropeptide-W (NPW) are recently discovered endogenous ligands of the GPR7- and GPR8-receptors (R), which in humans are expressed in the hypothalamus and probably involved in the regulation of energy homeostasis and neuroendocrine axes. GPR8-Rs are absent in rodents, where the GPR8-like-R has been described. Reverse transcription-polymerase chain reaction detected the expression of NPB, NPW, GPR7-R and GPR8-like-R mRNAs in rat adrenocortical cells (both freshly-dispersed and 4-day-cultured cells). NPB did not acutely (60-min exposure) alter basal aldosterone secretion from freshly dispersed zona glomerulosa cells, while NPW raised it. Both NPB and NPW enhanced ACTH-stimulated aldosterone secretion and did not affect either basal or ACTH-stimulated corticosterone production by dispersed zona fasciculata/reticularis (ZF/R) cells. The prolonged (4-day) exposure to NPW, but not NPB, raised corticosterone secretion from cultured ZF/R cells, and both neuropeptides increased the proliferation rate of cultured cells. Taken together, our findings indicate that NPB and NPW affect rat adrenocortical function, so they may be included in that large family of peptides involved in the autocrine-paracrine stimulation of secretion and growth of adrenal cortex.

Adrenal Cortex↗

PubMed2004

Biological fate of tissue-engineered porcine valvular conduits xenotransplanted in the sheep thoracic aorta.

The ideal prosthesis to replace the diseased human aortic valve is not yet available. We have previously shown that porcine acellular aortic-valve conduits, obtained by detergent-enzymatic method, display hemodynamic performances similar to those of their native counterparts. Hence, it seemed worthwhile to ascertain whether these tissue-engineered prostheses can be successfully xenotransplanted. Porcine acellular conduits, which immunocytochemistry demonstrated to lack MHC class I and II antigens, were implanted in the thoracic aorta of 9 sheep. Two animals died just after surgery, and the other 7 sheep were sacrificed 1 or 5 months after transplantation. A rather favorable outcome of the implant was observed in 4 sheep. In these animals, aortic valves remained pliable and coaptive, and the luminal surface of the conduits was endothelized just after one month from surgery. An intense inflammatory response was present at 1 month, and, although attennuated, it persisted for 5 months, located mainly between the tunica intima and media and at the border of the implant. Vimentin-positive and smooth muscle actin-positive myofibroblasts proliferated within tunica media and adventitia, and an obvious thickening of the tunica intima was also observed. Small vessels were seen in the adventitia, and elastic fibers were well-preserved in both the aorta wall and valve leaflets. In the cases of unfavorable outcome (3 of 7 survived sheep), implants were detached from the aorta recipient and surrounded by a connective mass that almost completely obstructed their lumen. These masses were composed of a fibromyxoid background where proliferating cells, resembling those occurring in human reactive myofibroblastic lesions (proliferative fascitis), were embedded. Collectively, these rather disappointing findings indicate that acellular valve conduits, obtained by the detergent-enzymatic method, are presently not suitable for clinical applications because of the persistent inflammatory response, which conceivably triggers overgrowth mechanisms that lead to implant failure.

Animals↗

PubMed2004

Adrenomedullin and endothelin-1 stimulate in vitro expansion of cord blood hematopoietic stem cells.

The improvement of techniques for in vitro expansion of cord blood (CB) hematopoietic stem cells (SCs) is, at present, one main task of tissue engineering. Hence, we investigated whether endothelin-1 (ET-1) and adrenomedullin (AM), two regulatory peptides exerting growth promoting action on several cell systems, favor the in vitro expansion of CB SCs in liquid culture. CB hematopoietic cell middle-term expansion was carried out in a stroma-free liquid culture medium in the presence of ET-1, AM and three different cytokine combinations. After two weeks of incubation, aliquots of expanded-cell suspension were seeded on semisolid medium and clonogenic tests were carried out by counting the number of colony forming units (CFUs) after 14 days of culture. Neither ET-1 nor AM (2.5 x 10(-8) M) were per se able to significantly increase the CFU number, but both peptides magnified the pro-expansive effects of some cytokine cocktails. In light of these findings, we conclude that ET-1 and AM are to be considered novel promising molecules that, in association with cytokines, can be utilized as pro-expansive factors of CB SCs in prevision of their clinical use in allogeneic transplantation.

Adrenomedullin↗

PubMed2003

Altered regulation of endothelin A receptor subtype in the cerebral arterioles in response to a Japanese-style diet, in stroke-prone hypertensive rats.

OBJECTIVE: To investigate the expression of endothelin (ET)-1 and its receptors in the cerebral arterioles of stroke-prone (spSHR) and control spontaneously hypertensive rats (SHRs) and the changes in endothelin receptor subtypes A and B density elicited by a stroke-permissive diet, before the development of stroke. METHODS: Six-week-old SHRs (n=11) and spSHRs (n=11) were assigned to either a regular or a "Japanese"-style diet, in addition to 1% NaCl in the drinking water, for 4 weeks. Cryosections (10 microm thick) of rat brain were assessed for endothelin receptor distribution and density by autoradiography with [125I]ET-1 (10(-10) mol/l) in the presence of cold ET-1 (10(-6) mol/l) or the peptide antagonists BQ-123 (10(-6) mol/l) or BQ-788 (10(-6) mol/l). Reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry were used to detect specific mRNAs and localize immunoreactive ET-1 and ET(A) and ET(B). RESULTS: In both strains, immunoreactive ET-1 was detected in the endothelium of cerebral arterioles, and RT-PCR and autoradiography demonstrated the coexistence of both receptor subtypes in brain homogenates and the cerebral arteriole walls, respectively. With the regular diet, the ET(A) receptor density was lower in SHRs than in spSHRs (P = 0.007), whereas the ET(B) receptor density was similar (P = NS). The Japanese-style diet increased the density of ET(A) receptors (P = 0.006) in SHRs, but decreased it (P = 0.019) in spSHRs. No effect was seen on ET(B) receptor density. CONCLUSIONS: ET(A) and ET(B) receptor subtypes are expressed in the wall of cerebral arterioles of SHRs and spSHRs. The latter strain showed a marked increase in ET(A) receptor density under a regular diet, in addition to an altered regulation in response to a stroke-permissive diet.

Animals↗

PubMed2003

Human skin keratinocytes and fibroblasts express adrenomedullin and its receptors, and adrenomedullin enhances their growth in vitro by stimulating proliferation and inhibiting apoptosis.

Adrenomedullin (ADM) is a hypotensive peptide, which originates from the proteolytic cleavage of pro(p)ADM and acts via two subtypes of receptors, named L1-R (L1-R) and calcitonin-receptor-like receptor (CRLR). L1-R is selective for ADM depending on the expression of the subtype 1 or the subtypes 2 and 3 of a family of chaperones, called receptor-activity-modifying proteins (RAMPs). Compelling evidence indicates that ADM, in addition to regulating blood pressure and water and electrolyte balance, also exerts a major growth promoting action in several normal and neoplastic cells. Reverse transcription (RT)-polymerase chain reaction (PCR) allowed the detection of pADM, L1-R and CRLR mRNAs in cultured human skin keratinocytes and fibroblasts. RAMP1 and RAMP2 (but not RAMP3) mRNAs were present, but their level of expression was rather weak, thereby suggesting that L1-R is the main subtype of ADM receptor in both keratinocytes and fibroblasts. ADM concentration-dependently raised the proliferation rate and lowered the apoptotic rate of both keratinocytes and fibroblasts cultured in vitro, maximal effective concentration being 10(-8) M. The effects of 10(-8) M ADM was annulled by the putative ADM-receptor antagonist ADM22-52 (10(-6) M). ADM22-52 also lowered basal proliferative activity of keratinocytes and fibroblasts, without affecting their apoptotic deletion rate. Taken together, these findings allow us to conclude that i) human skin keratinocytes and fibroblasts express ADM and its receptors; and ii) endogenous ADM system promotes the growth of keratinocytes and fibroblasts cultured in vitro, by enhancing their proliferative activity and lowering their apoptotic deletion.

Adrenomedullin↗

PubMed2002

Rat thyroid gland expresses the long form of leptin receptors, and leptin stimulates the function of the gland in euthyroid non-fasted animals.

Leptin is an adipose tissue-secreted hormone, which decreases caloric intake and increases energy expenditure. Some effects of leptin on energy balance seem to be mediated by the hypothalamo-pituitary-thyroid axis. The present study was designed to ascertain whether i) rat thyroid gland expresses the long form of leptin receptor (ObRb) and ii) the prolonged leptin administration (daily subcutaneous injections of 24 nmol/kg leptin for 6 consecutive days) affects thyroid-gland function in this species. Coupled RT-PCR, Western blotting and immunocytochemical findings demonstrated the expression of Ob-Rb as mRNA and protein in the thyroid gland of normal rats. Prolonged leptin treatment raised thyroid-gland weight, and morphometry showed that in the enlarged glands the volume of the follicle epithelium was increased, while that of colloid remained unchanged, so that epithelium/colloid ratio was markedly lowered. In leptin-administered rats, the plasma concentration of TSH was decreased, while those of thyroid hormones (free T3 and total T4) were notably raised. Collectively, these findings suggest that systemically administered leptin stimulates growth and secretion of thyroid gland in the rat, through a direct mechanism involving Ob-Rb.

Animals↗