Cation selective channel in fetal alveolar type II epithelium

Orser, Beverley A.; Bertlik, Maria; Fedorko, Ludwik; O’Brodovich, Hugh

doi:10.1016/0167-4889(91)90021-o

Cited by 73 publications

(37 citation statements)

References 29 publications

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“…(2) a moderately Na¤-selective (PNaÏPK 4) channel, with an intermediate single channel conductance of 7-15 pS; and (3) a non-selective cation channel (PNaÏPK 1), with a relatively large single channel conductance of 23-30 pS (Orser et al 1991;Palmer, 1992;Marunaka et al 1994;Tohda et al 1994;Marunaka, 1996;Marunaka et al 1997;Jain et al 1998). The characterization of these amiloridesensitive channels indicates an interesting relationship between Na¤ selectivity and single channel conductance: the single channel conductance increases as the Na¤ selectivity decreases.…”

Section: Discussionmentioning

confidence: 99%

Regulation of an amiloride‐sensitive Na⁺‐permeable channel by a β₂‐adrenergic agonist, cytosolic Ca²⁺ and Cl⁻ in fetal rat alveolar epithelium

Marunaka

Niisato

O’Brodovich

et al. 1999

The Journal of Physiology

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It is well known that the fetal lung epithelium secretes fluid into the lumen of the lung throughout gestation (for review see O 'Brodovich, 1991;Kemp & Olver, 1996). The fetal lung fluid plays an important role in development, differentiation and growth of the fetal lung. On the other hand, this fluid must be cleared from alveolar air spaces immediately after birth to allow normal gas exchange. Fluid clearance at birth appears to be enhanced by âµ-adrenergic stimulation of the alveolar epithelium (Brown et al. 1983). âµ-Adrenergic agonists promote lung fluid clearance by stimulating amiloride-sensitive Na¤ absorption (Olver et al. 1981; O'Brodovich et al. 1990a,b). Epithelial Na¤ channels (ENaCs) similar to those first cloned from rat colon (Canessa et al. 1993(Canessa et al. , 1994 appear to play a critical role in lung liquid clearance at birth (Hummler et al. 1996).There have been two types of Ca¥-activated, amilorideblockable Na¤-permeable channel described in fetal rat alveolar epithelium; one is a non-selective cation (NSC) channel with a single channel conductance of 28 pS, and the other is a Na¤ channel with a single channel conductance of 12 pS (Marunaka, 1996). However, only the 28 pS NSC channel responds to âµ-adrenergic stimulation implying that âµ-adrenergic agonists stimulate the amiloride-sensitive Na¤ absorption by activating the 28 pS NSC channel (Marunaka, 1997a;Marunaka & Niisato, 1999). We have previously reported that cytosolic Ca¥ and terbutaline, a âµ-adrenergic agonist, increase the open probability (Pï) of the 28 pS NSC channel (Marunaka et al. 1992;Tohda et al. 1994) and that cytosolic Cl¦ has an inhibitory action on the channel (Tohda et al. 1994). However, the gating mechanism

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Section: Discussionmentioning

confidence: 99%

Regulation of an amiloride‐sensitive Na⁺‐permeable channel by a β₂‐adrenergic agonist, cytosolic Ca²⁺ and Cl⁻ in fetal rat alveolar epithelium

Marunaka

Niisato

O’Brodovich

et al. 1999

The Journal of Physiology

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“…We studied primary cultures of FLE because these cells possess the bioelectric characteristics of sodium transporting epithelia and, similar to in vivo studies, transport sodium via sodium channels (3,16,17). Cells were studied in the presence or absence of aldosterone because this hormone might affect the response of the epithelium to AVP (7,9, 1 1 ,18,19).…”

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Arginine Vasopressin and Atrial Natriuretic Peptide Do Not Alter Ion Transport by Cultured Fetal Distal Lung Epithelium

1992

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ABSTRAa. Previous studies have shown that i.v. arginine vasopressin (AVP) decreases but does not stop lung fluid secretion in term fetuses not in labor. Although it has been presumed that the response to AVP results from augmented sodium transport, there is controversy whether AVP actually does affect sodium transport in mammalian lung epithelium. To determine if AVP or aldosterone could alone or together augment sodium transport in the perinatal lung, we studied primary cultures of fetal rat distal lung epithelium in Ussing chambers. The short circuit current of these sodium-transporting cells was not affected by the application of either 30 or 300 mU/mL AVP whether or not they were previously exposed to aldosterone M). Aldosterone also did not affect the baseline bioelectric properties. Short circuit current increased in response to 8-bromo cAMP M) and 3-isobutyl-1-methylxanthine M) to levels 169 f 16 (SEM) and 172 f 7% of respective baseline values. AVP had no effect in cells pretreated with 3-isobutyl-1-methylxanthine. Monolayers also did not respond to atrial natriuretic peptide (lo-" to lo-' M). Monolayers of Na-absorbing A6 renal epithelium did increase short circuit current with either aldosterone or AVP. AVP increased endogenous cAMP levels in A6 but not fetal rat distal lung epithelium cells, suggesting that fetal rat distal lung epithelium lacks V2 receptors. These studies demonstrate that AVP does not increase ion ' transport in cultured fetal distal lung epithelium although these cells possess the necessary second messenger system. (Pediatr Res 31: 318-322,1992) Abbreviations AVP, arginine vasopressin FLE, fetal rat distal lung epithelium Isc, short circuit current IBMX, isobutyl-1-methylxanthine 8 Br, bromoadenosine HBSS, Hanks' balanced salt solution PD, potential difference R, resistance ANP, atrial natriuretic peptide MEM, minimum essential medium At birth, the newborn lung is filled with fluid, which must be cleared before efficient gas exchange can take place. Epithelial have demonstrated that the sodium transport blocker amiloride can block p-agonist-induced fluid absorption in the fetal lamb lung ( 1 ) and delay fluid clearance in newborn guinea piglets (2). Studies using amiloride analogs have also suggested that the ability of amiloride to delay postnatal lung water clearance results from its blockade of epithelial sodium channels (3). To investigate mechanisms that could increase this perinatal lung epithelial sodium transport, we chose to study AVP because it reduces fluid secretion in fetal goats ( 4 ) and lambs ( 5 ) and circulates in the fetus in increased concentrations during normal delivery (6).Numerous studies (e.g. Refs. 7-1 1 ) have demonstrated that AVP can increase sodium transport in some non-lung tissues by increasing the number of active membrane-associated sodium channels (10). It is unknown whether these observations can be extrapolated to different species or to different epithelial membranes. For example, it has been reported that the AVP increases sodium transport i...

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“…To examine the possibility that fetal and adult alveolar cells use similar apical Na+ transport pathways, we attempted to determine if this channel is also present in adult alveolar epithelial cells. Part of this work was previously published in abstract form ( 17).…”

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“…22 Na+ flux measurements from membrane vesicles prepared from adult alveolar epithelium and whole-cell patch-clamp recordings support the presence of amiloride-sensitive Na+ channels (13,14). Recently, an amiloride-sensitive channel which was permeable to Na+ and K+ was identified in fetal alveolar epithelium (15,16). To examine the possibility that fetal and adult alveolar cells use similar apical Na+ transport pathways, we attempted to determine if this channel is also present in adult alveolar epithelial cells.…”

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A Nonselective Cation Channel in Adult Alveolar Epithelial Cells

Orser

Edelson

1994

Canadian Respiratory Journal

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OBJECTIVE: Efficie nt gas exchange across the alveolar membrane requires a dry air space. At birth, active Na+ transport provides the major driving force for absorption of fetal lung liquid, and during adult life, similar transport mechanisms balance fluid exchange across the alveolarcapillary membrane. A cation channel, previously identified in fetal a lveolar epithe lium, may represent o ne of several pathways which regulate apical-basal transepithelial Na+ flux. The purpose of this study was to determine if cation channels are a lso present in adult al veolar epithelial cells. DESIGN: Standard inside-out patch-clamp recording techniques were used to study channels present in patches of membrane from adult rat alveolar epithelium. Un canal cationique non selectif dans les cellules epitheliales alveolaires de l'adulte OB.JECTIF : Pour etre efficace, !es echanges gazeux a travers la membrane alveolaire exigent un espace aerien sec. A la naissance, le transport actif du Na+ fournit la force motrice pour !'absorption du liquide pulmonaire foetal. A !'age adulte, des mecanismes de transport similaires regulent Jes echanges liquidiens a travers la membrane alveolo-capillaire. Un canal cationique detecte anterieurement dans !'epithelium alveolaire foetal pourrait representer l'une des differentes voies de conduction qui regule le flux apico-basal transepithelial du sodium. L'objet de cette etude etait de determiner si des canaux cationiques etaient aussi presents dans les cellules epitheliales alveolaires de l'adulte. MODELE : Utilisation de la technique du patch-clamp exposant la face cytoplasmique des canaux pour etudier les canaux presents dans les fragments membranaires de !'epithelium alveolaire du rat adulte. POPULATION : Des cellules epitheliales alveolaires ont ete prelevees chez des rats Sprague-Dawley, males, adultes, et etudiees par culture cellulaire primaire. PRINCIPAUX RESULTAlS: On a identifie Lill canal cationique 23 pS non selectif dans 68 % des fragments au potentiel impose de -60 mY. La probabilite de l'ouverture d'un canal n' a pas ete influencee par les variations de potentiel transmembranaire. De l'amiloride ( I 0-5 M) applique sur la membrane extracellulaire a induit une stimulation du canal et a reduit le temps moyen apparent de l'ouverture du canal sans en affecter la conductance. CONCLUSIONS : Ces resultats fournssent la preuve directe de I' existence d' un canal cationique dans la membrane apicale des cellules epitheliales alveolaires de l' adulte. Le canal est identique a un canal cationique non selecti f identifie dans les cellules epitheliales alveolaires foetales et peut jouer un role important dans la reabsorption liquidienne couplee au Na+ et/ou dans la secretion du K+.

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Cation selective channel in fetal alveolar type II epithelium

Cited by 73 publications

References 29 publications

Regulation of an amiloride‐sensitive Na⁺‐permeable channel by a β₂‐adrenergic agonist, cytosolic Ca²⁺ and Cl⁻ in fetal rat alveolar epithelium

Regulation of an amiloride‐sensitive Na⁺‐permeable channel by a β₂‐adrenergic agonist, cytosolic Ca²⁺ and Cl⁻ in fetal rat alveolar epithelium

Arginine Vasopressin and Atrial Natriuretic Peptide Do Not Alter Ion Transport by Cultured Fetal Distal Lung Epithelium

A Nonselective Cation Channel in Adult Alveolar Epithelial Cells

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Cation selective channel in fetal alveolar type II epithelium

Cited by 73 publications

References 29 publications

Regulation of an amiloride‐sensitive Na+‐permeable channel by a β2‐adrenergic agonist, cytosolic Ca2+ and Cl− in fetal rat alveolar epithelium

Regulation of an amiloride‐sensitive Na+‐permeable channel by a β2‐adrenergic agonist, cytosolic Ca2+ and Cl− in fetal rat alveolar epithelium

Arginine Vasopressin and Atrial Natriuretic Peptide Do Not Alter Ion Transport by Cultured Fetal Distal Lung Epithelium

A Nonselective Cation Channel in Adult Alveolar Epithelial Cells

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Regulation of an amiloride‐sensitive Na⁺‐permeable channel by a β₂‐adrenergic agonist, cytosolic Ca²⁺ and Cl⁻ in fetal rat alveolar epithelium

Regulation of an amiloride‐sensitive Na⁺‐permeable channel by a β₂‐adrenergic agonist, cytosolic Ca²⁺ and Cl⁻ in fetal rat alveolar epithelium