Immunoexpression of Aquaporin-1 in the Efferent Ducts of the Rat and Marmoset Monkey during Development, Its Modulation by Estrogens, and Its Possible Role in Fluid Resorption*

Abstract Recent data suggest that estrogens play a role in regulating fluid resorption from the efferent ducts, though the biochemical mechanisms involved are unknown. The present study has used immunocytochemistry to localize a water channel protein, Aquaporin-1 (AQP-1), to the efferent ducts of male rats and marmoset monkeys from perinatal life through to adulthood and has then investigated its potential hormonal regulation in neonatal/peripubertal life, via administration of a GnRH antagonist (GnRHa) or diethylstilbestrol (DES) to rats. AQP-1 was immunoexpressed intensely in the apical brush border of the epithelium lining the efferent ducts at all ages studied, from late fetal life through puberty to adulthood. In the marmoset, but not the rat, AQP-1 was also expressed in the epithelium of the rete testis. Once the cell types within the efferent duct epithelium had differentiated, it was clear that only nonciliated cells of the rat localized AQP-1. When gonadotropin secretion was suppressed in rats by neonatal administration of GnRHa, immunoexpression of AQP-1 at age 18 and 25 days was virtually unchanged in intensity, though the efferent ducts were reduced in size. In contrast, when DES was administered neonatally to rats (up to day 12), immunoexpression of AQP-1 was reduced at day 10, virtually abolished at day 18, reduced markedly at day 25 and to a small extent at day 35; these findings were confirmed by Western blot analysis at day 18. The DES-induced decrease in immunoexpression of AQP-1 was accompanied by pronounced distension of the efferent ducts and rete, consistent with reduced fluid resorption. The epithelial cells of the efferent ducts in DES-treated rats were cuboidal rather than columnar in shape as in controls and were reduced significantly in height compared with controls at all ages through to adulthood. These findings suggest that estrogens may play a role in regulating fluid resorption from the efferent ducts during fetal/neonatal development and/or a role in the gross and functional development of the efferent ducts and rete testis. The present data also suggest that AQP-1 is one of the elements involved in the regulation of fluid resorption in the efferent ducts. The importance of fluid flow in fetal/neonatal development of the excurrent duct system of the male is also suggested by these observations.

Download Full-text

Immunolocalisation of oestrogen receptor-α within the testis and excurrent ducts of the rat and marmoset monkey from perinatal life to adulthood

Journal of Endocrinology ◽

10.1677/joe.0.1530485 ◽

1997 ◽

Vol 153 (3) ◽

pp. 485-495 ◽

Cited By ~ 182

Author(s):

J S Fisher ◽

M R Millar ◽

G Majdic ◽

P T K Saunders ◽

H M Fraser ◽

...

Keyword(s):

Sertoli Cells ◽

Leydig Cells ◽

Oestrogen Receptor ◽

Reproductive Tract ◽

Rete Testis ◽

Male Rat ◽

Fetal Life ◽

Male Reproductive Tract ◽

Marmoset Monkey ◽

Efferent Ducts

Abstract The sites of action and the physiological role of oestrogens in the male reproductive tract are poorly understood. We have undertaken a systematic study of the immunoexpression of oestrogen receptor-α (ERα) in the male rat from late fetal life through to adulthood and compared the findings with results obtained in the marmoset monkey (Callithrix jacchus) from neonatal to adult life. The testes, rete testis, efferent ducts and epididymis were examined from normal male rats (aged 4, 8, 10, 15, 20, 25, 38, 48 and 90 days) and from male rat fetuses on days 17·5 and 18·5 of gestation; comparable tissues were examined from neonatal, infantile, peripubertal and adult marmosets aged 8, 18–24, 54–62 and 92–112 weeks respectively. Immunolocalisation of ERa used antigen retrieval and a monoclonal antibody directed to the N-terminus, which had proved superior to six other antisera tested. ERa was immunoexpressed in interstitial cells, including the fetal/neonatal generation of Leydig cells, in both the rat and marmoset. In the rat, the adult generation of Leydig cells were also immunopositive for ERa whereas the comparable cells in the marmoset were only weakly immunopositive. ERa was not expressed in Sertoli cells, peritubular myoid cells, blood vessels or germ cells at any time in either species. In late fetal life in the rat, ERa was immunoexpressed in cells surrounding the mesonephric tubules, whereas postnatally it was expressed in the epithelium of the rete testis and efferent ducts at all ages from 4 to 90 days; this immunoexpression was most pronounced in the efferent ducts. In the marmoset, the efferent ducts, but not the rete testis, also showed intense immunoexpression of ERa. Apart from sporadic immunostaining for ERa in the epididymal duct of the rat in the neonatal period, the caput, corpus and cauda epididymis were negative for immunoexpression of ERa at all ages in both species. These findings suggest that the main actions of oestrogens in the male reproductive tract, mediated by ERa, are related to the development and function of the efferent ducts and the Leydig cells. In consideration of data from this and previous studies of oestrogen binding, we predict possible sites of expression of other oestrogen receptors (e.g. ERβ) in Sertoli cells and the epididymis. Interactive effects, related to the relative levels of androgens and oestrogens, could be physiologically important in the excurrent ducts of the adult testis. Journal of Endocrinology (1997) 153, 485–495

Download Full-text

Aquaporin-1: New Developments and Perspectives for Peritoneal Dialysis

Peritoneal Dialysis International ◽

10.3747/pdi.2010.00032 ◽

2010 ◽

Vol 30 (2) ◽

pp. 135-141 ◽

Cited By ~ 16

Author(s):

Olivier Devuyst ◽

Andrea J. Yool

Keyword(s):

Peritoneal Dialysis ◽

Water Transport ◽

Water Channel ◽

Cell Types ◽

Convective Transport ◽

Osmotic Gradient ◽

Pharmacological Agents ◽

Solute Permeability ◽

Chemical Screening ◽

Aquaporin 1

Peritoneal dialysis involves diffusive and convective transport and osmosis through the highly vascularized peritoneal membrane. Several lines of evidence have demonstrated that the water channel aquaporin-1 (AQP1) corresponds to the ultrasmall pore predicted by the model of peritoneal transport. Proof-of-principle studies have shown that upregulation of the expression of AQP1 in peritoneal capillaries results in increased water permeability and ultrafiltration, without affecting the osmotic gradient or small solute permeability. Conversely, studies in Aqp1 mice have shown that haplo-insufficiency for AQP1 results in significant attenuation of water transport. Recent studies have demonstrated that AQP1 is involved in the migration of different cell types, including endothelial cells. In parallel, chemical screening has identified lead compounds that could act as antagonists or agonists of AQPs, with description of putative binding sites and potential mechanisms of gating the water channel. By modulating water transport, these pharmacological agents could have clinically relevant effects in targeting specific tissues or disease states.

Download Full-text

Ca2+ Mediates HIF-dependent Upregulation of Aquaporin 1 in Pulmonary Arterial Smooth Muscle Cells

10.1101/2021.12.06.471473 ◽

2021 ◽

Author(s):

Xin Yun ◽

Haiyang Jiang ◽

Gregg L. Semenza ◽

Larissa A. Shimoda

Keyword(s):

Transcriptional Regulation ◽

Smooth Muscle ◽

Water Channel ◽

Cell Types ◽

Pulmonary Vasculature ◽

Arterial Smooth Muscle ◽

Aquaporin 1 ◽

Pulmonary Arterial ◽

Pulmonary Arterial Smooth Muscle ◽

Transcriptional Target

ABSTRACTProlonged exposure to hypoxia causes structural remodeling and sustained contraction of the pulmonary vasculature, resulting in the development of pulmonary hypertension. Both pulmonary arterial smooth muscle cell (PASMC) proliferation and migration contribute to the vascular remodeling. We previously showed that the protein expression of aquaporin 1 (AQP1), a membrane water channel protein, is elevated in PASMCs during following in vivo or in vitro exposure to hypoxia. Studies in other cell types suggest that AQP1 is a direct transcriptional target of hypoxia inducible factor (HIF)-1. Moreover, we and others have shown that an increase in intracellular calcium concentration ([Ca2+]i) is a hallmark of hypoxic exposure in PASMCs. Thus, we wanted to determine whether HIF regulates AQP1 in PASMCs and, if so, whether the process occurred via transcriptional regulation or was Ca2+-dependent. PASMCs were exposed to hypoxia, incubated with DMOG, which inhibits HIFα protein degradation or infected with constitutively active forms of HIF-1α or HIF-2α. Hypoxia, DMOG and HIF1/2α produced a time-dependent increase in AQP1 protein, but not mRNA. Interestingly, incubation with increasing HIF1/2α levels and DMOG increased [Ca2+]i in PASMCs, and this elevation was prevented by the voltage-gated Ca2+ channel inhibitor, verapamil (VER) and nonselective cation channel inhibitor SKF96365 (SKF). VER and SKF also blocked upregulation of AQP1 protein by DMOG or HIF1/2α, but had no effect on expression of GLUT1, a canonical HIF transcriptional target. Silencing of AQP1 abrogated increases in PASMC migration and proliferation induced by HIF1/2α, suggesting induction of AQP1 protein by HIF1/2α has a functional outcome in these cells. Thus, our results show that contrary to reports in other cell types, in PASMCs, AQP1 does not appear to be a direct target for HIF transcriptional regulation. Instead, AQP1 protein may be upregulated by a mechanism involving HIF-dependent increases in [Ca2+]i.

Download Full-text

Addendum to ?Regulation of the water channel aquaporin-1: isolation and reconstitution of the regulatory complex? 6Cell Boil. Int. 28(1) (2004) 7?719

Cell Biology International ◽

10.1016/s1065-6995(04)00053-8 ◽

2004 ◽

Author(s):

R ABUHAMDAH

Keyword(s):

Water Channel ◽

Aquaporin 1 ◽

Regulatory Complex

Download Full-text

Taking a Step Back: Insights into the Mechanisms Regulating Gut Epithelial Dedifferentiation

International Journal of Molecular Sciences ◽

10.3390/ijms22137043 ◽

2021 ◽

Vol 22 (13) ◽

pp. 7043

Author(s):

Shaida Ouladan ◽

Alex Gregorieff

Keyword(s):

Cell Fate ◽

Hormonal Regulation ◽

Transcriptional Profiling ◽

Cell Types ◽

Lineage Tracing ◽

Intestinal Stem Cells ◽

Physical Damage ◽

Epithelial Regeneration ◽

Gut Epithelium ◽

Stem Cell Populations

Despite the environmental constraints imposed upon the intestinal epithelium, this tissue must perform essential functions such as nutrient absorption and hormonal regulation, while also acting as a critical barrier to the outside world. These functions depend on a variety of specialized cell types that are constantly renewed by a rapidly proliferating population of intestinal stem cells (ISCs) residing at the base of the crypts of Lieberkühn. The niche components and signals regulating crypt morphogenesis and maintenance of homeostatic ISCs have been intensely studied over the last decades. Increasingly, however, researchers are turning their attention to unraveling the mechanisms driving gut epithelial regeneration due to physical damage or infection. It is now well established that injury to the gut barrier triggers major cell fate changes, demonstrating the highly plastic nature of the gut epithelium. In particular, lineage tracing and transcriptional profiling experiments have uncovered several injury-induced stem-cell populations and molecular markers of the regenerative state. Despite the progress achieved in recent years, several questions remain unresolved, particularly regarding the mechanisms driving dedifferentiation of the gut epithelium. In this review, we summarize the latest studies, primarily from murine models, that define the regenerative processes governing the gut epithelium and discuss areas that will require more in-depth investigation.

Download Full-text

Molecular sieving of small solutes by outer medullary descending vasa recta

AJP Renal Physiology ◽

10.1152/ajprenal.1997.272.5.f579 ◽

1997 ◽

Vol 272 (5) ◽

pp. F579-F586 ◽

Cited By ~ 7

Author(s):

T. L. Pallone ◽

M. R. Turner

Keyword(s):

Water Channel ◽

Fluorescein Isothiocyanate ◽

Pressure Gradients ◽

Volume Flux ◽

Aquaporin 1 ◽

A Value ◽

Vasa Recta ◽

Mathematical Simulations ◽

Molecular Sieving ◽

Hydrophilic Solutes

Molecular sieving of small solutes by outer medullary descending vasa recta (OMDVR). Descending vasa recta (DVR) plasma equilibrates with the medullary interstitium by volume efflux (Jv), as well as by influx of solutes. Jv is driven by transmural osmotic pressure gradients due to small hydrophilic solutes (delta pi s), NaCl and urea. DVR endothelium probably contains a "water-only" pathway most likely mediated by the aquaporin-1 (AQP1) water channel. We measured the ability of microperfused OMDVR to concentrate lumenal 22Na and [3H]raffinose when Jv was driven by transmural NaCl gradients. Collectate-to-perfusate ratios of 2 x 10(6) M(r) fluorescein isothiocyanate-labeled dextran volume marker (RDx), 22Na (RNa), and [3H]raffinose (Rraf) were measured in the absence and presence of Jv. During volume efflux (Jv > 0), RDx was 1.37 +/- 0.31. RNa increased from 0.64 +/- 0.03 when Jv = 0 to 0.82 +/- 0.05 when Jv > 0 and Rraf increased from 0.83 +/- 0.03 to 1.13 +/- 0.05: Mathematical simulations predict RNa and Rraf most accurately when the OMDVR reflection coefficient to the tracers is assigned a value near unity. This indicates that the OMDVR wall contains a pathway for osmotic volume flux that excludes small hydrophilic solutes, a behavior consistent with that of aquaporins.

Download Full-text

Electrophysiological evidence that systemic angiotensin influences rat area postrema neurons

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1990.258.1.r70 ◽

1990 ◽

Vol 258 (1) ◽

pp. R70-R76 ◽

Cited By ~ 3

Author(s):

S. Papas ◽

P. Smith ◽

A. V. Ferguson

Keyword(s):

Nucleus Tractus Solitarius ◽

Area Postrema ◽

Cell Types ◽

Male Rats ◽

Ang Ii ◽

Adrenergic Agonist ◽

Arterial Blood ◽

Spontaneous Activities ◽

Single Unit Recordings ◽

Body Fluid Balance

Extracellular single-unit recordings from neurons in the area postrema (AP) and the nucleus tractus solitarius (NTS) in anesthetized male rats demonstrated that most cells in these regions have spontaneous activities of 5 Hz or less. Systemic angiotensin (ANG II) (50-500 ng) enhanced the activity of 55% of AP cells tested (n = 76), whereas 53% of tested NTS neurons (n = 62) were inhibited by ANG II. To determine whether these neurons were influenced specifically by circulating ANG II or by the accompanying increase in mean arterial blood pressure (BP), the effects of adrenergic agonists given intravenously on ANG II influenced neurons were also examined. Subsequently two cell types were characterized: cells responding to iv ANG II but not to the adrenergic agonist ("ANG II sensitive") and cells responding in a similar way to both agents ("BP sensitive"). Most ANG II-responsive neurons in the AP (53.5%) and the NTS (65%) were determined to be BP sensitive. These data demonstrate that ANG II influences the activity of AP neurons. In addition, there exists a second population of AP neurons apparently responsive to perturbations of the cardiovascular system. These studies further emphasize the potential roles of the AP in the regulation of body fluid balance.

Download Full-text

Transepithelial water and urea permeabilities of isolated perfused Munich-Wistar rat inner medullary thin limbs of Henle's loop

AJP Renal Physiology ◽

10.1152/ajprenal.00491.2013 ◽

2014 ◽

Vol 306 (1) ◽

pp. F123-F129 ◽

Cited By ~ 13

Author(s):

C. Michele Nawata ◽

Kristen K. Evans ◽

William H. Dantzler ◽

Thomas L. Pannabecker

Keyword(s):

Water Channel ◽

Wistar Rat ◽

Structural Features ◽

Urea Transporter ◽

Outer Medulla ◽

Aquaporin 1 ◽

Passive Mechanism ◽

Short Loop ◽

Osmotic Water ◽

Gene Expression Levels

To better understand the role that water and urea fluxes play in the urine concentrating mechanism, we determined transepithelial osmotic water permeability ( Pf) and urea permeability ( Purea) in isolated perfused Munich-Wistar rat long-loop descending thin limbs (DTLs) and ascending thin limbs (ATLs). Thin limbs were isolated either from 0.5 to 2.5 mm below the outer medulla (upper inner medulla) or from the terminal 2.5 mm of the inner medulla. Segment types were characterized on the basis of structural features and gene expression levels of the water channel aquaporin 1, which was high in the upper DTL (DTLupper), absent in the lower DTL (DTLlower), and absent in ATLs, and the Cl-1 channel ClCK1, which was absent in DTLs and high in ATLs. DTLupper Pf was high (3,204.5 ± 450.3 μm/s), whereas DTLlower showed very little or no osmotic Pf (207.8 ± 241.3 μm/s). Munich-Wistar rat ATLs have previously been shown to exhibit no Pf. DTLupper Purea was 40.0 ± 7.3 × 10−5 cm/s and much higher in DTLlower (203.8 ± 30.3 × 10−5 cm/s), upper ATL (203.8 ± 35.7 × 10−5 cm/s), and lower ATL (265.1 ± 49.8 × 10−5 cm/s). Phloretin (0.25 mM) did not reduce DTLupper Purea, suggesting that Purea is not due to urea transporter UT-A2, which is expressed in short-loop DTLs and short portions of some inner medullary DTLs close to the outer medulla. In summary, Purea is similar in all segments having no osmotic Pf but is significantly lower in DTLupper, a segment having high osmotic Pf. These data are inconsistent with the passive mechanism as originally proposed.

Download Full-text