PubMed Health⌕ Search

Biomedical subjects

M Svelto

Publications and source records attributed to M Svelto.

At least 19 recordsLinked to original sources
PubMed2006

Effects of chronic treatment with statins and fenofibrate on rat skeletal muscle: a biochemical, histological and electrophysiological study.

BACKGROUND AND PURPOSE: Skeletal muscle injury by hypolipidemic drugs is not fully understood. An extensive analysis of the effect of chronic treatment with fluvastatin (5 mgkg(-1) and 20 mgkg(-1)), atorvastatin (10 mgkg(-1)) and fenofibrate (60 mgkg(-1)) on rat skeletal muscle was undertaken. EXPERIMENTAL APPROACH: Myoglobinemia as sign of muscle damage was measured by enzymatic assay. Histological and immunohistochemical techniques were used to estimate muscle integrity and the presence of aquaporin-4, a protein controlling water homeostasis. Electrophysiological evaluation of muscle Cl(-) conductance (gCl) and mechanical threshold (MT) for contraction, index of intracellular calcium homeostasis, was performed by the two-intracellular microelectrodes technique. KEY RESULTS: Fluvastatin (20 mgkg(-1)) increased myoglobinemia. The lower dose of fluvastatin did not modify myoglobinemia, but reduced urinary electrolytes, suggesting direct effects on renal function. Atorvastatin also increased myoglobinemia, with slight effects on urinary parameters. No treatment caused any histological damage to muscle or modification in the number of fibres expressing aquaporin-4. Either fluvastatin (at both doses) or atorvastatin reduced sarcolemma gCl and changed MT. Both statins produced slight effects on total cholesterol, suggesting that the observed modifications occur independently of HMGCoA-reductase inhibition. Fenofibrate increased myoglobinemia and decreased muscle gCl, whereas it did not change the MT, suggesting a different mechanism of action from the statins. CONCLUSIONS AND IMPLICATIONS: This study identifies muscle gCl and MT as early targets of drugs action that may contribute to milder symptoms of myotoxicity, such as muscle cramps, while the increase of myoglobinemia is a later phenomenon.

Action Potentials↗
PubMed2006

Aquaporin-2 excretion and renal function during the 1st week of life in preterm newborn infants.

In many preterm infants, a characteristic pattern of fluid and electrolyte homeostasis occurs during the 1st week of life, consisting of three phases: prediuretic, diuretic, and postdiuretic. In this study, we evaluated the possible role of aquaporin-2 (AQP2) in renal concentrating ability and correlated it with other markers of the renal function in healthy preterm infants. Daily urine and spot blood samples were collected from 9 healthy preterm (32 +/- 1 weeks) infants at postnatal ages 1, 3, and 7 days. Urine and serum osmolality, creatinine, electrolytes, and AQP2 excretion were measured. All infants showed a significant (about 7%) weight loss on day 3 associated with a more than threefold increase in urine output without a significant change in fluid intake (diuretic phase). The creatinine clearance increased on day 3, indicating an increase in glomerular filtration rate. Interestingly, on day 3, the level of total excreted AQP2 (pmol/h) was significantly higher when compared to day 1 and day 7, and the same tendency was observed for urine osmolality. To conclude, the observed increase in urine osmolality and creatinine clearance during the diuretic phase, paralleled by an increase in total AQP2 excretion, suggests that AQP2 can contribute to the urinary concentrating ability early in postnatal life.

Aquaporin 2↗
PubMed2005

Expression and subcellular localization of the AQP8 and AQP1 water channels in the mouse gall-bladder epithelium.

BACKGROUND INFORMATION: Transepithelial transport of water is one of the most distinctive functions by which the gall-bladder rearranges its bile content. Water is reabsorbed from the gall-bladder lumen during fasting, whereas it is secreted into the lumen following meal ingestion. Nevertheless, the molecular mechanism by which water is transported across the gall-bladder epithelium remains mostly unclear. RESULTS: In the present study, we investigate the presence and subcellular localization of AQP (aquaporin) water channels in the mouse gall-bladder epithelium. Considerable AQP8 mRNA was detected in the gall-bladder epithelium of mouse, calf, rabbit, guinea pig and man. Studies of subcellular localization were then addressed to the mouse gall-bladder where the transcript of a second AQP, AQP1, was also detected. Immunoblotting experiments confirmed the presence of AQP8 and AQP1 at a protein level. Immunohistochemistry showed intense expression of AQP8 and AQP1 in the gall-bladder epithelial cells where AQP8 was localized in the apical membrane, whereas AQP1 was seen both in the apical and basolateral membranes, and in vesicles located in the subapical cytoplasm. CONCLUSIONS: The pattern of subcellular distribution of AQP8 and AQP1 strongly corroborates the hypothesis of a transcellular route for the movement of water across the gall-bladder epithelium. Osmotic water would cross the apical membrane through AQP8 and AQP1, although AQP1 would be the facilitated pathway for the movement of water across the basolateral membrane. The presence of two distinct AQPs in the apical membrane is an unusual finding and may relate to the membrane's ability both to absorb and secrete fluid. It is tempting to hypothesize that AQP1 is hormonally translocated to the gall-bladder apical membrane to secrete water as in the bile duct epithelium, a functional homologue of the gall-bladder epithelium, whereas apical AQP8 may account for the absorption of water from gall-bladder bile.

Amino Acid Sequence↗
PubMed2005

Altered expression of aquaporin 4 and H(+)/K(+)-ATPase in the stomachs of peptide YY (PYY) transgenic mice.

BACKGROUND INFORMATION: The hormone PYY (peptide YY), synthesized by endocrine cells in the pancreas, ileum, colon and stomach has widespread inhibitory effects on gastrointestinal and pancreatic fluid secretion. Transgenic mice expressing a viral oncoprotein under the control of the PYY gene 5'-flanking region develop well-differentiated colonic endocrine tumours producing mainly PYY and enteroglucagon. In the present study, we investigated the expression of AQP4 (aquaporin 4) water channel and H(+)/K(+)-ATPase in stomachs from both control and transgenic mice. RESULTS: Semi-quantitative RT (reverse transcriptase)-PCR showed an increase in the AQP4 transcript compared with control mice. Quantitative Western-blot analysis of stomachs from control and transgenic mice confirmed a significant increase in the 30 kDa AQP4 protein in transgenic mice. In control mice, AQP4 is specifically expressed in the basolateral membrane of gastric parietal cells, located in the basal region of the fundic glands. This particular location suggests that parietal cells in the base region of gastric pits might have a major role in water transport when compared with the more superficial parietal cells. Interestingly, immunofluorescence studies on transgenic mice revealed that the quantitative increase of AQP4 expression was actually due to an increase in the number of AQP4-expressing epithelial cells rather than to a higher expression of AQP4 in parietal cells. In fact, immunofluorescence experiments using the specific antibody raised against the AE2 isoform of Cl(-)/HCO3- exchanger specifically expressed in parietal cells confirmed that the number of parietal cells was comparable in both PYY and control stomachs. Moreover, in transgenic mice, a parallel significant decrease in the expression of H(+)/K(+)-ATPase was observed, as revealed by RT-PCR, quantitative immunoblotting and immunofluorescence. CONCLUSIONS: In the present study, we demonstrate that the sustained inhibition of gastric secretion due to tumours producing PYY/enteroglucagon in transgenic mice is associated with an increase in AQP4 expression and a down-regulation of H(+)/K(+)-ATPase in parietal cells that acquire the characteristics of basal parietal cells. The absence of H2 receptors-mediated signalling due to the inhibition of histamine release from ECL (enterochromaffin-like) cells by PYY may be in part responsible for the observed increase in the number of parietal cells expressing AQP4.

Animals↗
PubMed2004

DNA adducts, benzo(a)pyrene monooxygenase activity, and lysosomal membrane stability in Mytilus galloprovincialis from different areas in Taranto coastal waters (Italy).

The aim of this study was to investigate the impact of environmental pollution at different stations along the Taranto coastline (Ionian Sea, Puglia, Italy) using several biomarkers of exposure and the effect on mussels, Mytilus galloprovincialis, collected in October 2001 and October 2002. Five sampling sites were compared with a "cleaner" reference site in the Aeronautics Area. In this study we also investigated the differences between adduct levels in gills and digestive gland. This Taranto area is the most significant industrial settlement on the Ionian Sea known to be contaminated by polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls, heavy metals, etc. Exposure to PAHs was evaluated by measuring DNA adduct levels and benzo(a)pyrene monooxygenase activity (B(a)PMO); DNA adducts were analyzed by 32P-postlabeling with nuclease P1 enhancement in both gills and digestive glands to evaluate differences between DNA adduct levels in the two tissues. B(a)PMO was assayed in the microsomal fraction of the digestive glands as a result of the high expression of P450-metabolizing enzymes in this tissue. Lysosomal membrane stability, a potential biomarker of anthropogenic stress, was also evaluated in the digestive glands of mussels, by measuring the latent activity of beta-N-acetylhexosaminidase. Induction of DNA adducts was evident in both tissues, although the results revealed large tissue differences in DNA adduct formation. In fact, gills showed higher DNA adduct levels than did digestive gland. No significant differences were found in DNA adduct levels over time, with both tissues providing similar results in both years. DNA adduct levels were correlated with B(a)PMO activity in digestive gland in both years (r = 0.60 in 2001; r = 0.73 in 2002). Increases were observed in B(a)PMO activity and DNA adduct levels at different stations; no statistical difference was observed in B(a)PMO activity over the two monitoring campaigns. The membrane labilization period in mussels from some stations was decreased in both years. No statistical differences were established in the membrane labilization times from 2001 to 2002. Our results suggest the existence of different sources and amounts of environmental contaminants at the stations investigated. The formation of DNA adducts confirms the existence of activation pathways in mussels and shows the importance of DNA adduct analysis in the gill tissue in addition to the more commonly used digestive gland; these results confirm the utility of lysosomal membrane stability as a biomarker of general stress. Overall, the integrated use of biomarkers of exposure and the effects of environmental contaminants on living marine organisms may help to better interpret the impact of pollutants in a marine coastal environment.

Animals↗
PubMed2004

Altered blood-brain barrier development in dystrophic MDX mice.

In order to ascertain whether the alterations of the blood-brain barrier (BBB) seen in adult dystrophic mdx-mice [Glia 42 (2003) 235], a human model of Duchenne muscular dystrophy (DMD), are developmentally established and correlated with other dystrophin isoforms which are localized at the glial-vascular interface, we used immunocytochemistry to investigate the expression of dystrophin isoforms (Dp71) during BBB development in mdx fetuses and in adult mice. Parallelly, we used Western blot, immunocytochemistry and immunogold electron microscopy to analyze the expression of the zonula occludens (ZO-1), aquaporin-4 (AQP4) and glial fibrillary acidic (GFAP) proteins as endothelial and glial markers, and we evaluated the integrity of the mdx BBB by means of intravascular injection of horseradish peroxidase (HRP). The results show reduced dystrophin isoforms (Dp71) in the mdx mouse compared with the control, starting from early embryonic life. Endothelial ZO-1 expression was reduced, and the tight junctions were altered and unlabeled. AQP4 and GFAP glial proteins in mdx mice also showed modifications in developmental expression, the glial vascular processes being only lightly AQP4- and GFAP-labeled compared with the controls. Confocal microscopy and HRP assays confirmed the alteration in vessel glial investment, GFAP perivascular endfoot reactivity being strongly reduced and BBB permeability increasing. These results demonstrate that a reduction in dystrophin isoforms (Dp71) at glial endfeet leads to an altered development of the BBB, whose no-closure might contribute to the neurological dysfunctions associated with DMD.

Animals↗
PubMed2004

The role of aquaporin-4 in the blood-brain barrier development and integrity: studies in animal and cell culture models.

Aquaporin-4 (AQP4) is the major water channel expressed in brain perivascular astrocyte processes. Although the role of AQP4 in brain edema has been extensively investigated, little information exists regarding its functional role at the blood-brain barrier (BBB). The purpose of this work is to integrate previous and recent data regarding AQP4 expression during BBB formation and depending on BBB integrity, using several experimental models. Results from studies on the chick optic tectum, a well-established model of BBB development, and the effect of lipopolysaccharide on the BBB integrity and on perivascular AQP4 expression have been analyzed and discussed. Moreover, data on the BBB structure and AQP4 expression in murine models of Duchenne muscular dystrophy are reviewed. In particular, published results obtained from mdx(3cv) mice have been analyzed together with new data obtained from mdx mice in which all the dystrophin isoforms including DP71 are strongly reduced. Finally, the role of the endothelial component on AQP4 cellular expression and distribution has been investigated using rat primary astrocytes and brain capillary endothelial cell co-cultures as an in vitro model of BBB.

Animals↗
PubMed2003

Possible functional implications of aquaporin water channels in reproductive physiology and medically assisted procreation.

Spermatogenesis, the maturation of spermatozoa and their concentration and storage in the seminiferous vessels are associated with considerable fluid secretion or absorption in the male reproductive tract. These fluid movements are in total agreement with the presence of multiple aquaporin (AQP) water channel proteins in germ cells and other tissues within the male reproductive tract. A series of functions of prime importance have already been hypothesized for aquaporins in the physiology of male reproduction. Aquaporins could be involved in the early stages of spermatogenesis, in the secretion of tubular liquid and in the concentration and storage of spermatozoa in the epididymis. In the male reproductive tract, alterations in the expression and functionality and/or regulation of aquaporins have already been demonstrated to be at the basis of forms of male infertility. Indeed, rats with reduced reabsorption of seminiferous fluid in the efferent ducts have been shown to be sub-fertile or infertile. Functions have also been suggested in the fertilization process, where aquaporins may play a role in maintaining osmotic homeostasis in gametes during fertilization. Aquaporins have also been suggested to mediate water movement into antral follicles and to be the pathway for transtrophectodermal water movement during cavitation. Aquaporins are the subject of considerable technological interest for cryopreservation used in medically assisted procreation, as they could be the molecular pathway by which water and/or solutes move across the plasma membrane during the process of freezing/thawing gametes and embryos. Indeed, artificial expression ofAQP3 has been showed to improve the survival of mouse oocytes after cryopreservation.

Aquaporins↗
PubMed2001

Possible involvement of aquaporin-7 and -8 in rat testis development and spermatogenesis.

Fluid secretion and reabsorption are of central importance in male reproductive (MR) physiology. However, the related molecular mechanisms are poorly known. Here, potential roles for AQP7 and AQP8, two aquaporin water channels abundantly expressed in the MR tract, were investigated by studying their expression and distribution in the developing testis of the Wistar rat. By semiquantitative RT-PCR and immunoblotting, first expression of AQP7 was noted at postnatal day 45 (P45), with levels increasing substantially at P90 and remaining at high levels thereafter. AQP8 began to be expressed at P15, rapidly increased until P20, and remained fairly stable thereafter. Immunohistochemical analyses demonstrated AQP7 in elongated spermatids, testicular spermatozoa, and residual bodies at P45 with increased signal intensity thereafter. AQP8 was observed in primary spermatocytes from P20 to P30 and, in elongated spermatids, residual bodies and Sertoli cells at P30 and thereafter. The ontogeny and distribution of AQP7 and AQP8 in rat testis suggest involvement in major physiologic changes in testis development and spermatogenesis.

Animals↗
PubMed2001

Histamine treatment induces rearrangements of orthogonal arrays of particles (OAPs) in human AQP4-expressing gastric cells.

To test the involvement of the water channel aquaporin (AQP)-4 in gastric acid physiology, the human gastric cell line (HGT)-1 was stably transfected with rat AQP4. AQP4 was immunolocalized to the basolateral membrane of transfected HGT-1 cells, like in native parietal cells. Expression of AQP4 in transfected cells increased the osmotic water permeability coefficient (Pf) from 2.02 +/- 0.3 x 10-4 to 16.37 +/- 0.5 x 10-4 cm/s at 20 degrees C. Freeze-fracture EM showed distinct orthogonal arrays of particles (OAPs), the morphological signature of AQP4, on the plasma membrane of AQP4-expressing cells. Quantitative morphometry showed that the density of OAPs was 2.5 +/- 0.3% under basal condition and decreased by 50% to 1.2 +/- 0.3% after 20 min of histamine stimulation, mainly due to a significant decrease of the OAPs number. Concomitantly, Pf decreased by approximately 35% in 20-min histamine-stimulated cells. Both Pf and OAPs density were not modified after 10 min of histamine exposure, time at which the maximal hormonal response is observed. Cell surface biotinylation experiments confirmed that AQP4 is internalized after 20 min of histamine exposure, which may account for the downregulation of water transport. This is the first evidence for short term rearrangement of OAPs in an established AQP4-expressing cell line.

Animals↗
PubMed2001

Microvessel overexpression of aquaporin 1 parallels bone marrow angiogenesis in patients with active multiple myeloma.

The erythrocyte water channel aquaporin 1 (AQP1) is expressed in multiple absorptive and secretory epithelia including the capillary endothelia. Immunoblot analysis showed that bone marrow biopsies of patients with active multiple myeloma (MM) display significantly higher levels of AQP1 than those from patients with non-active MM, whose values are higher, but to a lesser extent, than those of patients with monoclonal gammopathies of undetermined significance (MGUS). Values of MGUS overlapped those of patients with anaemia as a result of iron or vitamin B12 deficiencies (called 'benign anaemias'). Immunohistochemistry and computerized image analysis of AQP1 highlighted bone marrow microvessels whose area per microscopic field was significantly greater in patients with active MM, and always larger than and closely correlated with the microvessel area when assessed with factor VIII-related antigen/von Willebrand's factor (FVIII-VWF). The intensity of AQP1 expression by microvessels evaluated using image analysis was significantly greater in active than non-active MM and in the latter over MGUS or benign anaemias. It is suggested that, among plasma cell tumours, AQP1 expression is preferentially associated with microvessels of MM and that the highest degree of expression occurs in active MM in step with enhanced angiogenesis, in which AQP1 recognizes more immature neovessels than FVIII-VWF. It may, perhaps, favour angiogenesis in a positive loop and, hence, MM progression, and thus be applied for therapeutic vascular targeting.

Adult↗
PubMed2001

Expression and immunolocalization of the aquaporin-8 water channel in rat gastrointestinal tract.

A remarkable amount, of water is transported in the gastrointestinal (GI) organs to fulfil the secretory and absorptive functions of the GI tract. However, the molecular basis of water movement in the GI epithelial barriers is still poorly known. Important clues about the mechanisms by which water is transported in the GI tract were provided by the recent identification of multiple aquaporin water channels expressed in GI tissues. Here we define the mRNA and protein expression and the cellular and subcellular distribution of aquaporin-8 (AQP8) in the rat GI tract. By semi-quantitative RT-PCR the AQP8 mRNA was detected in duodenum, proximal jejunum, proximal colon, rectum, pancreas and liver and, to a lesser extent, in stomach and distal colon. Immunohistochemistry using affinity-purified antibodies revealed AQP8 staining in the absorptive epithelial cells of duodenum, proximal jejunum, proximal colon and rectum where labeling was largely intracellular and confined to the subapical cytoplasm. Confirming previous results, AQP8 staining was seen at the apical pole of pancreatic acinar cells. Interestingly, both light and immunoelectron microscopy analyses showed AQP8 reactivity in liver where labeling was associated to hepatocyte intracellular vesicles and over the plasma membrane delimiting the bile canaliculi. A complex pattern was observed by immunoblotting with total membranes of the above GI organs incubated with affinity-purified anti-AQP8 antibodies which revealed multiple bands with molecular masses ranging between 28 and 45 kDa. This immunoblotting pattern was not modified after deglycosylation with N-glycosidase F except the 34-kDa band of liver that, as already reported, was partially down-shifted to 28 kDa. No bands were detected after preadsorption of the anti-AQP8 antibodies with the immunizing peptide. The cellular and subcellular distribution of AQP8 suggest physiological roles for this aquaporin in the absorption of water in the intestine and the secretion of bile and pancreatic juice in liver and pancreas, respectively. The large intracellular expression of AQP8 may indicate its recycling between the cytoplasmic compartment and the plasma membrane. The cytoplasmic localization observed may also relate to the involvement of AQP8 in processes of intracellular osmoregulation.

Animals↗
PubMed2001

Expression and localization of the aquaporin-8 water channel in rat testis.

Spermatogenesis and sperm maturation and storage are accompanied by significant movements of water, and multiple aquaporin transmembrane water channels (AQPs) have been recognized in the male reproductive tract. Nevertheless, the involvement of aquaporins in male reproductive physiology is mostly unknown. Here the expression and localization of AQP8 in rat spermatogenesis is defined and compared to that of AQP7, another aquaporin expressed in male germ cells. AQP8 mRNA was found in testis but not in epididymis, whereas the AQP7 transcript was present in both locations. By immunoblotting, the AQP8 protein was detected as a 25-kDa band and a 32- to 40-kDa diffuse component corresponding to the core and glycosylated protein, respectively. Membrane fractionation revealed AQP8 both in microsomal and plasma membrane-enriched fractions of rat testis while no apparent bands were detected in epididymis. AQP7 appeared as a 23- to 24-kDa band and was found both in testis and epididymis. By immunofluorescence, AQP8 labeling was found intracellularly as well as over the plasma membrane of germ cells throughout spermatogenesis. AQP7 was present in spermatids and spermatozoa and was predominant over the plasma membrane. AQP8 may be involved in the cytoplasmic condensation occurring during differentiation of spermatids into spermatozoa and in the generation of seminiferous tubule fluid.

Animals↗
PubMed2001

Aquaporin-4 deficiency in skeletal muscle and brain of dystrophic mdx mice.

We report a detailed study of AQP4 expression in the neuromuscular system of mdx mice. Immunocytochemical analysis performed by double immunostaining revealed that mdx mice manifest a progressive reduction in AQP4 at the sarcolemmal level of skeletal muscle fast fibers and that type IIB fibers are the first to manifest this reduction in AQP4 expression. No labeling was observed in the cytoplasm of muscle fibers, indicating that the reduction in sarcolemma staining is not associated with an intracellular compartmentalization of mistargeted protein. By Western blot and RT-PCR analysis, we found that whereas the total content of AQP4 protein decreased (by 90% in adult mdx mice), mRNA levels for AQP4 remained unchanged. A similar age-related reduction in AQP4 expression was found in brain astrocytic end-feet surrounding capillaries of mdx mice. Morphometric analysis performed after immunogold electron microscopy indicated a reduction of approximately 85% in gold particles (32+/-2/microm vs. 4.7+/-0.61/microm). Western blot experiments conducted using membrane fractions from brain cortex revealed a strong reduction (of 70%) in AQP4 protein in adult mdx mice, and RT-PCR experiments demonstrated that the reduction was not at transcription level. More interesting was the finding that AQP4 reduction was associated with swelling of astrocytic perivascular processes whose ultrastructural modifications are commonly indicated as an important and early event in the development of brain edema. No apparent reduction in AQP4 was found in mdx stomach and kidney. Our data provide evidence that dystrophin deficiency in mdx mice leads to disturbances in AQP4 assembly in the plasma membrane of fast skeletal muscle fibers and brain astrocytic end-feet, suggesting that changes in the osmotic equilibrium of the neuromuscular apparatus may be involved in the pathology of muscular dystrophy.

Animals↗
PubMed2001

Rho inhibits cAMP-induced translocation of aquaporin-2 into the apical membrane of renal cells.

First published August 8, 2001; 10.1152/ajprenal.00091.2001.-We have recently demonstrated that actin depolymerization is a prerequisite for cAMP-dependent translocation of the water channel aquaporin-2 (AQP2) into the apical membrane in AQP2-transfected renal CD8 cells (29). The Rho family of small GTPases, including Cdc42, Rac, and Rho, regulates the actin cytoskeleton. In AQP2-transfected CD8 cells, inhibition of Rho GTPases with Clostridium difficile toxin B or with C. limosum C3 fusion toxin, as well as incubation with the Rho kinase inhibitor, Y-27632, caused actin depolymerization and translocation of AQP2 in the absence of the cAMP-elevating agent forskolin. Both forskolin and C3 fusion toxin-induced AQP2 translocation were associated with a similar increase in the osmotic water permeability coefficient. Expression of constitutively active RhoA induced formation of stress fibers and abolished AQP2 translocation in response to forskolin. Cytochalasin D induced both depolymerization of F-actin and AQP2 translocation, suggesting that depolymerization of F-actin is sufficient to induce AQP2 translocation. Together, these data indicate that Rho inhibits cAMP-dependent translocation of AQP2 into the apical membrane of renal principal cells by controlling the organization of the actin cytoskeleton.

Actins↗
PubMed2001

Tissue distribution and membrane localization of aquaporin-9 water channel: evidence for sex-linked differences in liver.

Aquaporin-9 (AQP9) is a water channel membrane protein also permeable to small solutes such as urea, glycerol, and 5-fluorouracil, a chemotherapeutic agent. With the aim of understanding the pathophysiological role of AQP9, we performed an extensive analysis by Western blotting, RT-PCR, and immunolocalization in rat tissues. Western blotting analysis revealed a major band of approximately 32 kD in testis, liver, and brain. Immunofluorescence showed strong expression of AQP9 in the plasma membrane of testis Leydig cells. In liver, AQP9 expression was found to be sex-linked. Male rats had higher levels of AQP9 than female in terms of both protein and mRNA. Moreover, in female livers the expression of AQP9 was mostly confined to perivascular hepatocytes, whereas males showed a more homogeneous hepatocyte staining. No differences in AQP9 expression level related to the age or to protein content of the diet were found, indicating that differences in the liver may be gender-dependent. In the brain, AQP9 expression was found in tanycytes mainly localized in the areas lacking a blood-brain barrier (BBB), such as the circumventricular organs (CVOs) of the third ventricles, the subfornical organ, the hypothalamic regions, and the glial processes of the pineal gland. AQP9 expression in the osmosensitive region of the brain suggests a role in the mechanism of central osmoreception. All these findings show a unique tissue distribution of AQP9 compared to the other known aquaporins.

Animals↗