Nonselective cation transport in native esophageal epithelia

2004 ◽  
Vol 287 (2) ◽  
pp. C395-C402 ◽  
Author(s):  
Mouhamed S. Awayda ◽  
Abderrahmane Bengrine ◽  
Nelia A. Tobey ◽  
James D. Stockand ◽  
Roy C. Orlando
Keyword(s):  
Potential Role ◽  
Basolateral Membrane ◽  
Culture Conditions ◽  
Cation Channel ◽  
Monovalent Cations ◽  
Nonselective Cation Channel ◽  
Artificial Culture ◽  
Electrophysiological Properties ◽  
Esophageal Epithelial Cells

Rabbit esophageal epithelia actively transport Na+ in a manner similar to that observed in classic electrically tight Na+-absorbing epithelia, such as frog skin. However, the nature of the apical entry step is poorly understood. To address this issue, we examined the electrophysiological and biochemical nature of this channel. Western blotting experiments with epithelial Na+ channel (ENaC) subunit-specific antibodies revealed the presence of all three ENaC subunits in both native and immortalized esophageal epithelial cells. The amino acid sequence of the rabbit α-ENaC cloned from native rabbit esophageal epithelia was not significantly different from that of other published α-ENaC homologs. To characterize the electrophysiological properties of this native apical channel, we utilized nystatin permeabilization to eliminate the electrical contribution of the basolateral membrane in isolated native epithelia mounted in Ussing-type chambers. We find that the previously described apical Na+ channel is nonselective for monovalent cations (Li+, Na+, and K+). Moreover, this channel was not blocked by millimolar concentrations of amiloride. These findings document the presence of a nonselective cation channel in a native Na+ transporting epithelia, a finding that hereto has been thought to be limited to artificial culture conditions. Moreover, our data are consistent with a potential role of ENaC subunits in the formation of a native nonselective cation channel.

Physiological Role of Ca2+-Permeable Nonselective Cation Channel in Endothelin-1-Induced Contraction of Rabbit Aorta

1997 ◽  
Vol 30 (4) ◽  
pp. 504-509 ◽  
Author(s):  
Taro Komuro ◽  
Soichi Miwa ◽  
Xiao-Feng Zhang ◽  
Tetsuya Minowa ◽  
Taijiro Enoki ◽  
...  
Keyword(s):  
Physiological Role ◽  
Rabbit Aorta ◽  
Cation Channel ◽  
Nonselective Cation Channel ◽  
Endothelin 1

A mechanogated nonselective cation channel in proximal tubule that is ATP sensitive

2002 ◽  
Vol 283 (1) ◽  
pp. F93-F104 ◽  
Author(s):  
Craig G. Hurwitz ◽  
Vivian Y. Hu ◽  
Alan S. Segal
Keyword(s):  
Proximal Tubule ◽  
Basolateral Membrane ◽  
Cation Channel ◽  
Transepithelial Transport ◽  
Single Channels ◽  
Epithelial Polarity ◽  
Nonselective Cation Channel ◽  
Channel Activity ◽  
Entry Pathway ◽  
Hypotonic Swelling

Ion channels that are gated in response to membrane deformation or “stretch” are empirically designated stretch-activated channels. Here we describe a stretch-activated nonselective cation channel in the basolateral membrane (BLM) of the proximal tubule (PT) that is nucleotide sensitive. Single channels were studied in cell-intact and cell-free patches from the BLM of PT cells that maintain their epithelial polarity. The limiting inward Cs+ conductance is ∼28 pS, and channel activity persists after excision into a Ca2+- and ATP-free bath. The stretch-dose response is sigmoidal, with half-maximal activation of about −19 mmHg at −40 mV, and the channel is activated by depolarization. The inward conductance sequence is: NH[Formula: see text] ∼ Cs+ ∼ Rb+> K+ ∼ Na+ ∼ Li+ > Ca2+ ∼ Ba2+> N-methyl-d-glucamine ∼ tetraethylammonium. The venom of the common Chilean tarantula, Grammostola spatulata, completely blocks channel activity in cell-attached patches. Hypotonic swelling reversibly activates the channel. Intracellular ATP concentration ([ATP]i) reversibly blocks the channel (inhibitory constant ∼0.48 mM), suggesting that channel function is coupled to the metabolic state of the cell. We conclude that this channel may function as a Ca2+ entry pathway and/or be involved in regulation of cell volume. We speculate this channel may be important when [ATP]i is depleted, as occurs during periods of increased transepithelial transport or with ischemic injury.

Sodium-Gated Cation Channel Implicated in the Activation of Lobster Olfactory Receptor Neurons

1998 ◽  
Vol 79 (3) ◽  
pp. 1349-1359 ◽  
Author(s):  
Aslbek B. Zhainazarov ◽  
Richard E. Doolin ◽  
Barry W. Ache
Keyword(s):  
Olfactory Receptor ◽  
Cation Channel ◽  
Olfactory Receptor Neurons ◽  
Substantial Part ◽  
Nonselective Cation Channel ◽  
Transduction Pathway ◽  
Ion Substitution ◽  
Receptor Neurons ◽  
Primary Odor

Zhainazarov, Aslbek B., Richard E. Doolin, and Barry W. Ache. Sodium-gated cation channel implicated in the activation of lobster olfactory receptor neurons. J. Neurophysiol. 79: 1349–1359, 1998. The role of Na+-activated channels in cellular function, if any, is still elusive. We have attempted to implicate a Na+-activated nonselective cation channel in the activation of lobster olfactory receptor neurons. We show that a Na+-activated channel occurs in the odor-detecting outer dendrites. With the use of pharmacological blockers of the channel together with ion substitution, we show that a substantial part of the odor-evoked depolarization in these cells can be ascribed to a Na+-activated conductance. We hypothesize, therefore, that the Na+-activated channel amplifies the receptor current as a result of being secondarily activated by the primary odor transduction pathway.

Role of phosphoinositide 3-kinase in the nonselective cation channel activation by endothelin-1/endothelinBreceptor

2003 ◽  
Vol 284 (2) ◽  
pp. C506-C510 ◽  
Author(s):  
Yoshifumi Kawanabe ◽  
Nobuo Hashimoto ◽  
Tomoh Masaki
Keyword(s):  
Chinese Hamster ◽  
Pi3k Pathway ◽  
Cation Channel ◽  
Channel Blockers ◽  
Nonselective Cation Channel ◽  
Channel Activation ◽  
Endothelin 1 ◽  
Ovarian Cells ◽  
Phosphoinositide 3 Kinase

We recently demonstrated that endothelin-1 (ET-1) activates two types of Ca2+-permeable nonselective cation channel (designated NSCC-1 and NSCC-2) in Chinese hamster ovarian cells expressing endothelinB receptor (CHO-ETBR). These channels can be discriminated using the Ca2+ channel blockers, LOE 908 and SK&F 96365. LOE 908 is a blocker of NSCC-1 and NSCC-2, whereas SK&F 96365 is a blocker of NSCC-2. In this study, we investigated the possible role of phosphoinositide 3-kinase (PI3K) in the ET-1-induced activation of NSCCs in CHO-ETBR using wortmannin and LY-294002, inhibitors of PI3K. ET-1-induced Ca2+ influx was partially inhibited in CHO-ETBR pretreated with wortmannin or LY-294002. In contrast, addition of wortmannin or LY-294002 after stimulation with ET-1 did not suppress Ca2+ influx. The Ca2+ channels activated by ET-1 in wortmannin- or LY-294002-treated CHO-ETBR were sensitive to LOE 908 and resistant to SK&F 96365. In conclusion, NSCC-2 is stimulated by ET-1 via PI3K-dependent cascade, whereas NSCC-1 is stimulated independently of the PI3K pathway. Moreover, PI3K seems to be required for the initiation of the Ca2+ entry through NSCC-2 but not for its maintenance.

Evidence for presence of functional beta-adrenoceptor in rabbit S2 proximal straight tubules

1991 ◽  
Vol 261 (3) ◽  
pp. F393-F399 ◽  
Author(s):  
K. Kudo ◽  
Y. Kondo ◽  
K. Abe ◽  
Y. Igarashi ◽  
K. Tada ◽  
...  
Keyword(s):  
Basolateral Membrane ◽  
Disulfonic Acid ◽  
K Channel ◽  
Dependent Manner ◽  
Electrophysiological Properties ◽  
Beta Adrenoceptor ◽  
Organic Solute ◽  
Cell Depolarization ◽  
Dose Dependent

The effect of isoproterenol on the electrophysiological properties of the S2 proximal segment of the rabbit was examined. Isoproterenol at 10(-8) to 10(-4) M depolarized the basolateral membrane voltage (Vb) in a dose-dependent manner. Propranolol attenuated the isoproterenol-induced depolarization. These possible mechanisms of cell depolarization were explored. The role of luminal Na(+)-organic solute cotransport was negligible, since the removal of organic solute did not change the depolarization. Basolateral Na(+)-(HCO3-) cotransport was supported by the finding that 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid inhibited isoproterenol-induced depolarization. Basolateral K+ conductance was suggested by the finding that the application of Ba2+ blocked the isoproterenol-induced depolarization. Na(+)-K(+)-adenosine-triphosphatase (ATPase) was questionable. Although ouabain blocked isoproterenol-induced depolarization, the removal of Na+ did not inhibit the depolarization. Further experiment revealed that dibutylyl-adenosine 3',5'-cyclic monophosphate (cAMP), 8-bromo cAMP, and forskolin did not mimic the response of isoproterenol. These results demonstrate: 1) there is a functional beta-adrenoceptor that depolarizes Vb; 2) isoproterenol-induced depolarization is due to an inhibition of basolateral K+ channel or the activation of basolateral Na(+)-(HCO3-)n cotransport; 3) isoproteronol-induced depolarization is independent of cAMP in the rabbit proximal tubule.

Sign in / Sign up

Export Citation Format

Share Document