Expression of Na,K‐ATPase alpha subunit isoforms in the human ciliary body and cultured ciliary epithelial cells

Martín‐Vasallo, Pablo; Ghosh, Sikha; Coca‐Prados, Miguel

doi:10.1002/jcp.1041410203

Cited by 67 publications

(31 citation statements)

References 42 publications

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“…We postulate that Cl-channels, especially cyclic AMP-dependent Cl-channels, may be localized predominantly on the aqueous side of NPE and serve as a final step of aqueous secretion from the NPE. Further investigation is required to explore the interaction of cyclic AMP-dependent Cl-channels with other transport systems such as Cl-/HCO3-exchange (Wolosin et al, 1989;Saito, 1992), Na', K+, Cl-cotransport (Mito et al, 1993) and Na+/K' pump (Usukawa et Martin-Vasallo et al, 1989), in aqueous humour production. A close link of cyclic AMP-dependent Cl-conductance to the Na+/K' pump has been reported in rabbit corneal epithelium (Klyce & Wong, 1977).…”

Section: Resultsmentioning

confidence: 99%

Role of cyclic AMP‐induced Cl conductance in aqueous humour formation by the dog ciliary epithelium

Chen

Inoue

Inomata

et al. 1994

British J Pharmacology

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1 The effects of isoprenaline, a forskolin derivative NKH-477, and dibutyryl cyclic AMP (db cyclic AMP) on the membrane potential, conductance and cell volume of the dog non-pigmented ciliary epithelium (NPE) were investigated by intracellular potential recording, nystatin-perforated patch clamp technique and videomicroscopic cytometry. 2 The resting membrane potential of NPE was about -70 mV in physiological saline and was depolarized by isoprenaline in a dose-dependent manner with an EDm of about 3 nM. This depolarization was competitively antagonized by the P-adrenoceptor antagonist, timolol (pA2 = ca. 9) and almost completely blocked by the Cl transport blocker, DIDS. 3 In single dissociated NPE cells, 10 jAM isoprenaline induced an inward current and caused a concomitant decrease in cell volume. The reversal potential measurement indicated that this inward current was carried mainly by Cl ion. DIDS (10 jM) abolished both the current and cell volume decrease. 4 NKH-477 (10 jAM) or db cyclic AMP (1 mM) also induced an inward current together with a cell volume decrease, the properties of which were similar to those caused by isoprenaline.5 These results suggest that P-adrenoceptor stimulation in NPE leads to an increased rate of aqueous humour production by increasing Cl-efflux via an elevation of cyclic AMP and this effect is efficiently blocked by timolol.

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Section: Resultsmentioning

confidence: 99%

Role of cyclic AMP‐induced Cl conductance in aqueous humour formation by the dog ciliary epithelium

Chen

Inoue

Inomata

et al. 1994

British J Pharmacology

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“…This study is not possible as serial AH sampling in the healthy eye would not merit ethical approval. An alternative is to move to an established in vitro model for evaluating NPE pathophysiology, the ODM-2 NPE cell line (Martin-Vasallo et al 1989, Civan et al 1996, Carre et al 2000, Rauz et al 2003c. Our preliminary studies, however, failed to demonstrate 11b-HSD1 oxo-reductase or dehydrogenase activity (S Rauz & E A Walker, unpublished observations) despite the expression at a mRNA level (Rauz et al 2001).…”

Section: Western Blot Analysesmentioning

confidence: 89%

Characterisation of the prereceptor regulation of glucocorticoids in the anterior segment of the rabbit eye

Onyimba¹,

Vijapurapu²,

Curnow³

et al. 2006

Journal of Endocrinology

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The prereceptor regulation of glucocorticoids (GCs) by 11b-hydroxysteroid dehydrogenase type-1 (11b-HSD1), a bidirectional isozyme that interconverts active (cortisol) and inactive (cortisone) GCs, is an established determinant of GC function in tissues such as liver, adipose and bone. Although the therapeutic use of GCs is abundant in ophthalmic practice, where GC interactions with nuclear receptors modulate gene transcription, the prereceptor regulation of endogenous cortisol is not well described in ocular tissues. Recent descriptive studies have localised 11b-HSD1 to the human corneal epithelium and non-pigmented epithelium (NPE) of the ciliary body, indicating a link to corneal epithelial physiology and aqueous humour production. In this study, we characterise the functional aspects of the autocrine regulation of GCs in the anterior segment of the rabbit eye. Using our in-house generated primary antibody to human 11b-HSD1, immunohistochemical analyses were performed on paraffin-embedded sections of whole New Zealand white albino rabbits, (NZWAR) eyes. As in human studies, 11b-HSD1 was localised to the corneal epithelium and the NPE. No staining was seen in the albino 'pigmented' ciliary epithelium. Specific enzyme assays for oxo-reductase (cortisone/cortisol) and dehydrogenase (cortisol/cortisone) activity indicated predominant 11b-HSD1 oxo-reductase activity from both the intact ciliary body tissue (nZ12, median 2$1 pmol/mg per h and range 1$25-2$8 pmol/mg per h; PZ0$006) and primary cultures of corneal epithelial cells (nZ12, median 3$0 pmol/mg per h and range 1$0-7$4 pmol/mg per h, PZ0$008) compared with dehydrogenase activity (median 1$0 pmol/mg per h and range 0$5-2$0 pmol/mg per h; median 0$5 pmol/mg per h and range 0$25-1$9 pmol/mg per h respectively). These findings were supported by expression of 11b-HSD1 protein as visualised by Western blotting of ciliary body tissue and immunocytochemistry of corneal epithelial cells. Reduction of corneal epithelial cell proliferation was seen after primary cultures were co-incubated with cortisol and cortisone. 11b-HSD1 activity was not demonstrated in naïve conjunctival fibroblasts or corneal stromal keratocytes. Our results indicate that the distribution of 11b-HSD1 in the rabbit resembles that of the human eye and activates cortisone to cortisol in both corneal and uveal tissues. The NZWAR provides a suitable in vivo model for the further evaluation of 11b-HSD1 activity in the eye, especially its role in corneal epithelial and ciliary body physiology.

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“…35) Thus far, 4a (a1, a2, a3, a4), 3b (b1, b2, b3) and 1g isoform subunits have been identified in mammals. [35][36][37][38] However, other isoforms may exist and the search is on for novel isoform subunits that may confer unique kinetic prop- erties on the enzyme complex. The different isoforms (a1, a2, a3, a4) of the a subunit are widely expressed in an organ-specific manner.…”

Section: Discussionmentioning

confidence: 99%

The Molecular Mechanism of Protective Effects of Grape Seed Proanthocyanidin Extract on Reperfusion Arrhythmias in Rats in Vivo

Zhao

Gao

Qiu

et al. 2010

Biological & Pharmaceutical Bulletin

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Early reperfusion is crucial for the survival of ischemic myocardium. However, reperfusion has been referred by Braunwald and Kloner 1) as the "double edged sword" because reperfusion itself may lead to accelerated and additional myocardial injury beyond that generated by ischemia alone. This results in a spectrum of reperfusion-associated pathologies, collectively called "reperfusion injury."2) Reperfusion injury has been observed in each of reperfusion therapies including percutaneous coronary intervention (PCI), thrombolysis and coronary bypass grafting. The different clinical manifestations of this injury include myocardial necrosis, myocardial apoptosis, reperfusion arrhythmias, myocardial stunning and endothelial-and microvascular dysfunction including the no-reflow phenomenon.3) However, ventricular tachycardia (VT) and ventricular fibrillation (VF) induced by reperfusion remain the most important causes of sudden death following spontaneous restoration of antegrade flow. 4,5) Therefore, every effort must be made to minimize sudden cardiac death caused by reperfusion arrhythmias. The mechanisms of reperfusion arrhythmias may include heterogeneous recovery of conduction and a refractory period of incomplete reperfusion, reentry, abnormal automaticities, and activities triggered by Ca 2ϩ overload and free radicals. [6][7][8][9] However, the details of the mechanisms remain unclear and reperfusion arrhythmia has not received satisfactory treatment.Grape seed proanthocyanidin extract (GSPE) is a natural, standardized, water-ethanol extract from red grape seeds which has great free radical scavenging ability. The main pharmacological effective components of GSPE are oligomeric proanthocyanidins. Free radicals and oxidative stress play a crucial role in the pathophysiology of a broad spectrum of cardiovascular diseases including congestive heart failure, valvular heart disease, cardiomyopathy, hypertrophy, atherosclerosis and ischemic heart disease. A series of studies were conducted using GSPE to demonstrate its cardioprotective ability in animals and humans. [10][11][12][13][14] Our previous work had shown GSPE reduced reperfusioninduced arrhythmias in rabbits. 15) In isolated rat hearts GSPE had been proved to reduce the incidence of reperfusion-induced VF and VT.11) However the mechanism of this protection against reperfusion-induced VT, VF by GSPE remained unclear. Proteomic studies of heart tissues can provide new insights into the specific early molecular mechanisms that underlie the responses to ischemia reperfusion (IR) injury and therefore may have vital implications for the specificity and efficacy of diagnosis and treatment. Despite their biological significance, the investigation of membrane proteomics is technically limited by the relatively high molecular masses and hydrophobicities of these proteins.16) With the development of proteomic techniques a quantitative proteomics-isobaric tags for relative and absolute quantification (iTRAQ) was introduced to solve these problems. iTRAQ employs prima...

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Expression of Na,K‐ATPase alpha subunit isoforms in the human ciliary body and cultured ciliary epithelial cells

Cited by 67 publications

References 42 publications

Role of cyclic AMP‐induced Cl conductance in aqueous humour formation by the dog ciliary epithelium

Role of cyclic AMP‐induced Cl conductance in aqueous humour formation by the dog ciliary epithelium

Characterisation of the prereceptor regulation of glucocorticoids in the anterior segment of the rabbit eye

The Molecular Mechanism of Protective Effects of Grape Seed Proanthocyanidin Extract on Reperfusion Arrhythmias in Rats in Vivo

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