scholarly journals Structural diversity of occluding junctions in the low-resistance chloride-secreting opercular epithelium of seawater-adapted killifish (Fundulus heteroclitus).

1980 ◽  
Vol 87 (2) ◽  
pp. 488-497 ◽  
Author(s):  
S A Ernst ◽  
W C Dodson ◽  
K J Karnaky
Keyword(s):  
Fundulus Heteroclitus ◽  
Short Circuit ◽  
Freeze Fracture ◽  
Short Circuit Current ◽  
Chloride Cells ◽  
Rectal Gland ◽  
Secretory Cells ◽  
Pavement Cells ◽  
Occluding Junctions ◽  
Mucosal Side

The structural features of the chloride-secreting opercular epithelium of seawater-adapted killifish (Fundulus heteroclitus) were examined by thin-section and freeze-fracture electron microscopy, with particular emphasis on the morphological appearance of occluding junctions. This epithelium is a flat sheet consisting predominantly of groups of mitochondriarich chloride cells with their apices associated to form apical crypts. These multicellular groups are interspersed in an otherwise continuous pavement cell epithelial lining. The epithelium may be mounted in Ussing-type chambers, which allow ready access to mucosal and serosal solutions and measurement of electrocal properties. The mean short-circuit current, potential difference (mucosal-side negative), and DC resistance for 19 opercular epithelia were, respectively, 120.0 +/- 18.2 microA/cm2, 12.3 +/- 1.7 mV, and 132.5 +/- 26.4 omega cm2. Short-circuit current, a direct measure of Cl- transport, was inhibited by ouabain (5 micron) when introduced on the serosal side, but not when applied to the mucosal side alone. Autoradiographic analysis of [3H]-ouabain-binding sites demonstrated that Na+,K+-ATPase was localized exclusively to basolateral membranes of chloride cells; pavement cells were unlabeled. Occluding junctions between adjacent chloride cells were remarkably shallow (20-25 nm), consisting of two parallel and juxtaposed junctional strands. Junctional interactions between pavement cells or between pavement cells and chloride cells were considerably more elaborate, extending 0.3-0.5 micron in depth and consisting of five or more interlocking junctional strands. Chloride cells at the lateral margins of crypts make simple junctional contacts with neighboring chloride cells and extensive junctions with contiguous pavement cells. Accordingly, in this heterogeneous epithelium, only junctions between Na+,K+-ATPase-rich chloride cells are shallow. Apical crypts may serve, therefore, as focal areas of high cation conductivity across the junctional route. This view is consistent with the electrical data showing that transmural resistance across the opercular eptihelium is low, and with recent studies demonstrating that transepithelial Na+ fluxes are passive. The simplicity of these junctions parallels that described recently for secretory cells of avian salt gland (Riddle and Ernst, 1979, J. Membr. Biol., 45:21-35) and elasmobranch rectal gland (Ernst et al., 1979, J. Cell Biol., 83:(2, Pt. 2):83 a[Abstr.]) and lends morphological support to the concept that paracellular ion permeation plays a central role in ouabain-sensitive transepithelial NaCl secretion.

Effect of atriopeptin II on isolated opercular epithelium of Fundulus heteroclitus

1988 ◽  
Vol 254 (1) ◽  
pp. R27-R32 ◽  
Author(s):  
J. I. Scheide ◽  
J. A. Zadunaisky
Keyword(s):  
Fundulus Heteroclitus ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Chloride Secretion ◽  
Chloride Cells ◽  
Induced Response ◽  
Ion Regulation ◽  
Cyclic Monophosphate ◽  
Stimulation Of

The effect of atriopeptin II (ANF) on the in vitro opercular epithelium was investigated by use of short-circuit current techniques. Serosal addition of ANF stimulates chloride secretion (short-circuit current) 19% above control values with a 7% increase in tissue conductance. Mucosal addition of ANF to the opercular epithelium was without effect. The ANF stimulation of the current was dose dependent with a maximum at 10(-7) M. The addition of ANF had no effect on the current or the conductance of opercular epithelia bathed in Cl--free Ringer. The opercular current could be stimulated above the ANF response by isoproterenol (10(-6) M). Pretreatment of the opercular epithelium with propranolol (10(-5) M) did not inhibit the stimulation of the short-circuit current by ANF but did inhibit the isoproterenol response indicating that the ANF stimulatory activity was independent of the beta-adrenergic receptors. The ANF-stimulated short-circuit current was found in operculi pretreated with tetrodotoxin (10(-6) or 10(-5) M) or diltiazem (10(-4) M) indicating the ANF response was not due to nerve stimulation. Pretreatment of opercular tissue with dibutyryl adenosine 3',5'-cyclic monophosphate, 8-bromoadenosine 3',5'-cyclic monophosphate, or 8-bromoguanosine 3',5'-cyclic monophosphate (10(-4) M) had no effect on the ANF stimulatory response. Opercular epithelia from short-term freshwater-adapted killifish also showed the ANF-induced response. The stimulation of chloride secretion in Fundulus heteroclitus chloride cells by ANF may have a role in teleost ion regulation.

Suppression of gastric acid secretion by furosemide in isolated gastric mucosa of guinea pig

1980 ◽  
Vol 239 (6) ◽  
pp. G532-G535 ◽  
Author(s):  
A. Ayalon ◽  
A. Corcia ◽  
G. Klemperer ◽  
S. R. Caplan
Keyword(s):  
Guinea Pig ◽  
Acid Secretion ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Electrical Conductance ◽  
Short Circuit Current ◽  
Cl Transport ◽  
Consequent Reduction ◽  
Net Flux ◽  
Mucosal Side

The effect of furosemide on acid secretion and Cl- transport was studied in isolated fundic mucosa of the guinea pig. Furosemide (10(-3) M), applied to the serosal side produced an immediate effect on the short-circuit current (Isc), lowering it by 47 +/- 2%. Potential difference decreased by 29 +/- 3%, electrical conductance by 18 +/- 4%, acid secretion by 38 +/- 1%, and net flux of Cl- from serosal-to-mucosal side by 37%. Application of the drug to the mucosal side produced similar effects on acid secretion and on the electrical parameters. It is suggested that furosemide blocks the entrance of Cl-, by the Na+--Cl- cotransport mechanism, through the basolateral membrane of the secreting cell. The consequent reduction in electrogenic Cl- transport would cause Isc and acid secretion to decrease. A reduction of Cl- conductance of the apical membrane, upon mucosal application of the drug, would cause similar effects on acid secretion and Cl- transport.

Avian cecum: role of glucose and volatile fatty acids in transepithelial ion transport

1991 ◽  
Vol 260 (5) ◽  
pp. G703-G710 ◽  
Author(s):  
B. R. Grubb
Keyword(s):  
Fatty Acids ◽  
Ion Transport ◽  
Volatile Fatty Acids ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Serosal Side ◽  
Na Transport ◽  
Cl Secretion ◽  
Mucosal Side

In the fowl cecum in vitro, the influence of glucose and the three most prevalent naturally occurring volatile fatty acids (acetate, propionate, butyrate) on short-circuit current (Isc), electrical resistance, and transport of Na and Cl was determined. When glucose, acetate, or butyrate was present, ion transport was characterized by electrogenic Na absorption, greater than 65% of which was amiloride inhibitable, and Cl secretion, which also was electrogenic. Isc could be completely accounted for by net fluxes of Na and Cl. When glucose, acetate, or butyrate (10 mM both sides) was included in the incubation medium, cecal tissue maintained its Isc and a constant rate of net Na absorption and Cl secretion for a 5-h period. When no substrate was present or propionate was included in the medium, a marked fall in Isc and net Na and Cl fluxes was seen. Glucose caused an increase in Isc when added only to the serosal side. As 3-O-methylglucose (not metabolized) was not effective in stimulating Isc of the cecum (serosal or mucosal addition), it appeared that glucose increased Isc by acting as an energy substrate for active Na transport. Acetate and butyrate appeared to be equally effective in stimulating Na transport and Isc when placed on either side of the membrane. When the preparation was supplied with glucose (serosal side) and acetate was added to the mucosal side, no further stimulation of Isc occurred. Thus it appeared that acetate and butyrate were acting as substrates for active Na transport rather than stimulating Na transport by some other mechanism such as a cotransport with Na.(ABSTRACT TRUNCATED AT 250 WORDS)

Segregation of gastric Na and Cl transport: a vibrating probe and microelectrode study

1986 ◽  
Vol 251 (4) ◽  
pp. C643-C648 ◽  
Author(s):  
J. R. Demarest ◽  
C. Scheffey ◽  
T. E. Machen
Keyword(s):  
Gastric Mucosa ◽  
Cell Membrane ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Cell Types ◽  
Open Circuit ◽  
Membrane Potentials ◽  
Vibrating Probe ◽  
Zero Current ◽  
Mucosal Side

The short-circuit current (Isc) of resting Necturus gastric mucosa (approximately 20 microA/cm2) can be attributed to the algebraic sum of the net Cl- secretion and amiloride-inhibitable net Na+ absorption. We have attempted to identify the cell types [surface epithelial cells (SCs) or oxyntic cells (OCs)] responsible for the transport of these ions in Necturus gastric mucosa using microelectrodes (ME) and a vibrating probe (VP). Mucosae were mounted horizontally in an open-topped Plexiglas chamber either serosal side up for basolateral ME impalements of OCs or mucosal side up for apical impalements of SCs and VP measurements. Cell impalements were made under open-circuit conditions, and VP measurements were performed under short-circuit conditions. Impalements of OCs indicate that neither the ratio of their apical to basolateral cell membrane resistances (Ra/Rb = 1.3 +/- 0.2) nor their cell membrane potentials were affected by 10(-6) M mucosal amiloride. In contrast, impalements of SCs indicate that amiloride increased their Ra/Rb from 3.5 +/- 0.2 to 15.6 +/- 1.8 and hyperpolarized both cell membrane potentials by greater than 20 mV. VP measurements showed that the amiloride-induced change in the current from SCs (5.6 microA/cm2) accounted for the amiloride-induced change in the Isc (5.5 microA/cm2). A non-zero current (4.4 +/- 1.0 microA/cm2) measured over SCs in the presence of amiloride was due to contamination from current arising from the gastric crypts that contain the OCs.(ABSTRACT TRUNCATED AT 250 WORDS)

Ion transport across cat and ferret tracheal epithelia

1986 ◽  
Vol 61 (3) ◽  
pp. 1065-1070 ◽  
Author(s):  
R. J. Corrales ◽  
D. L. Coleman ◽  
D. B. Jacoby ◽  
G. D. Leikauf ◽  
H. L. Hahn ◽  
...  
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Free Medium ◽  
Mucin Secretion ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Mucosal Side

Sheets of trachea from ferret and cat were mounted in Ussing chambers and continuously short circuited. Under resting conditions, in both the cat and ferret there was little or no Cl secretion, and Na absorption accounted for most of the short-circuit current (Isc). Ouabain (10(-4) M, serosal bath) reduced Isc to zero in 30–60 min. This decline was matched by a decrease in net Na absorption. Amiloride (10(-4) M, luminal bath) caused a significant decrease in Isc and conductance (G) in both species. Bumetanide (10(-4) M, serosal bath) had negligible effects on Isc and G. In both species, isoproterenol increased Isc by stimulating Cl secretion. Methacholine induced equal amounts of Na and Cl secretion, with little change in Isc. In the cat, prostaglandins E2 and F2 alpha and bradykinin increased Isc, responses which were abolished in Cl-free medium. In open-circuited cat tissues, Na flux from the serosal to mucosal side was measured simultaneously with the secretion of nondialyzable 35S. Prostaglandins E1, E2, and F2 alpha, histamine, bradykinin, methacholine and isoproterenol all increased both Na and 35S-mucin secretion.

scholarly journals Occluding junctions and cell behavior in primary cultures of normal and neoplastic mammary gland cells.

1975 ◽  
Vol 66 (2) ◽  
pp. 316-332 ◽  
Author(s):  
P B Pickett ◽  
D R Pitelka ◽  
S T Hamamoto ◽  
D S Misfeldt
Keyword(s):  
Primary Cultures ◽  
Freeze Fracture ◽  
Culture Conditions ◽  
Pavement Cells ◽  
Thin Sections ◽  
Occluding Junctions ◽  
Bulk Medium ◽  
Mammary Gland Cells ◽  
Junction Structure

Cells dissociated from normal prelactating mouse mammary glands or from spontaneous mammary adenocarcinomas, when grown at high density on an impermeable substrate, form nonproliferating, confluent, epithelial pavements in which turgid, blister-like domes appear as a result of fluid accumulation beneath the cell layer. To compare the structure of the fluid-segregating cell associations in normal and tumor cell cultures with that of lactating gland in vivo, we have examined such cultures alive and in thick and thin sections and freeze-fracture replicas. Pavement cells in all cases are polarized toward the bulk medium as a lumen equivalent, with microvilli and continuous, well-developed occluding junctions at this surface. Between the pavement and the substrate are other cells, of parenchymal or stromal origin, scattered or in loose piles; these sequestered cells are relatively unpolarized and never possess occluding junctions. Small gap junctions have been found in the pavement layer, and desmosomes may link epithelial cells in any location. Under the culture conditions used, development of the epithelial secretory apparatus is not demonstrable; normal and neoplastic cells do not differ consistently in any property examined. A dome's roof is merely a raised part of the epithelial pavement and does not differ from the latter in either cell or junction structure. We suggest that dome formation demonstrates the persistence of some transport functions and of the capacity to form effective occluding junctions. These basic epithelial properties can survive both neoplastic transformation and transition to culture.

scholarly journals Molecular mechanisms for intestinal HCO3- secretion and its regulation by guanylin in seawater-acclimated eels

2019 ◽  
Author(s):  
Yoshio Takei ◽  
Marty K.S. Wong ◽  
Masaaki Ando
Keyword(s):  
Hormonal Regulation ◽  
Time Course ◽  
Molecular Mechanisms ◽  
Apical Membrane ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Disulfonic Acid ◽  
Intestinal Epithelia ◽  
Mucosal Side

AbstractThe intestine of marine teleosts secretes HCO3- into the lumen and precipitates Ca2+ and Mg2+ in the imbibed seawater as carbonates to decrease luminal fluid osmolality and facilitate water absorption. However, reports on studies on the hormonal regulation of HCO3- secretion are just emerging. Here, we showed that guanylin (GN) applied to the mucosal side of intestinal epithelia increased HCO3- secretion in seawater-acclimated eels. The effect of GN on HCO3- secretion was slower than that on the short-circuit current, and the time-course of the GN effect was similar to that of bumetanide. Mucosal bumetanide and serosal 4,4’-dinitrostilbene-2,2’-disulfonic acid (DNDS) inhibited the GN effect, suggesting an involvement of apical Na+-K+-2Cl- cotransporter (NKCC2) and basolateral Cl-/HCO3- exchanger (AE)/Na+-HCO3- cotransporter (NBC) in the GN effect. However, mucosal DNDS and diphenylamine-2-carboxylic acid (DPC) failed to inhibit the GN effect, showing that apical AE and Cl- channel are not involved. To identify molecular species of possible transporters involved in the GN effect, we performed RNA-seq analyses followed by quantitative real-time PCR after transfer of eels to seawater. Among the genes upregulated after seawater transfer, those of Slc26a3a, b (DRAa, b) and Slc26a6a, c (Pat-1a, c) on the apical membrane of the intestinal epithelial cells, and those of Sls4a4a (NBCe1a), Slc4a7 (NBCn1), Slc4a10a (NBCn2a) and Slc26a1 (Sat-1) on the basolateral membrane were candidate transporters involved in HCO3- secretion. Judging from the slow effect of GN, we suggest that GN inhibits NKCC2b on the apical membrane and decreases cytosolic Cl- and Na+, which then activates apical DNDS-insensitive DRAa, b and basolateral DNDS-sensitive NBCela, n1, n2a to enhance transcellular HCO3- flux across the intestinal epithelia of seawater-acclimated eels.

Ileal mucosal cyclic AMP and Cl secretion: serosal vs. mucosal addition of cholera toxin.

1977 ◽  
Vol 232 (2) ◽  
pp. E210 ◽  
Author(s):  
H E Sheerin ◽  
M Field
Keyword(s):  
Cyclic Amp ◽  
Ion Transport ◽  
Cholera Toxin ◽  
Short Circuit ◽  
Electrical Conductance ◽  
Short Circuit Current ◽  
Serosal Side ◽  
Ileal Mucosa ◽  
Camp Content ◽  
Mucosal Side

Changes in ion transport and cyclic AMP (cAMP) concentration produced by addition of cholera toxin to the serosal side of isolated rabbit ileal mucosa (CTs) were compared to the changes produced by addition to the mucosal side (CTm). CTs increased short-circuit current (SCC) as did CTm but it did so more slowly. CTs, unlike CTm, did not significantly decrease electrical conductance. Inhibition of the SCC response to theophylline, a measure of preexisting secretion, was almost complete 180 min after CTm but was not yet significant 180 min after CTs. Longer (280 min) after CTs, the SCC response to theophylline was reduced by 59%, a significant reduction but less than that caused by CTm. A statistically significant change in net Cl flux could not be demonstrated after CTs, although at 280 min the measured flux was halfway between the fluxes for control and CTm tissues. Cyclic AMP concentrations were determined at 190 min, 10 min after addition of theophylline. CTs, despite little or no effect on ion transport, increased cAMP to the same level as did CTm, and the effect on cAMP of adding toxin to both sides was additive. We conclude that 1) active secretion is probably stimulated by cholera toxin added on the serosal side, although more slowly than after addition to the mucosal side and 2) much of the toxin-stimulated cAMP content of the mucosa is not coupled to secretion.

Phorbol ester and okadaic acid regulation of Na-2Cl-K cotransport in rabbit tracheal epithelial cells

1996 ◽  
Vol 271 (1) ◽  
pp. C338-C346 ◽  
Author(s):  
C. M. Liedtke ◽  
L. Thomas
Keyword(s):  
Epithelial Cells ◽  
Okadaic Acid ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Term Treatment ◽  
Secretory Cells ◽  
Adrenergic Stimulation ◽  
Short Term Treatment ◽  
Tracheal Epithelial Cells ◽  
Tracheal Epithelial

We evaluated a role for protein kinase C (PKC) in the regulation of rabbit tracheal epithelial Na-Cl(K) cotransport. Short-term treatment with phorbol 12-myristate 13-acetate (PMA) dose dependently increased bumetanide-sensitive Na and Cl efflux and elevated staurosporine- and bumetanide-sensitive Na, Cl, and K uptake. PMA and the alpha 2A-adrenergic agonist guanabenz both induced contransport with a stoichiometry of 2 Cl:1 Na and 2 Cl:1 Rb and elevated staurosporine-sensitive PKC activity in cytosolic and particulate fractions. Prolonged PMA treatment did not sustain bumetanide-sensitive 2 Cl:1 Na and 2 Cl:1 Rb transport but did block stimulation of bumetanide-sensitive transport by PMA or guanabenz and elevation of PKC activity by PMA and guanabenz in a particulate fraction. Cells treated with okadaic acid exhibited a staurosporine- and bumetanide-sensitive 2 Cl:1 Na and 2 Cl:1 Rb uptake. In cultured monolayers, basolateral perfusion with epinephrine, isoproterenol, or PMA increased short-circuit current (Isc). Basolateral application of bumetanide reduced elevated Isc to baseline levels, indicating a role for Cl secretory cells in a reconstituted tracheal epithelium. Pretreatment of transmonolayer cultures with PMA diminished the stimulatory response to epinephrine. These results indicate that, in rabbit tracheal epithelial cells, alpha-adrenergic stimulation activated Na-2Cl-K cotransport and that PKC is a critical effector in this process.

Introduction

1981 ◽  
Vol 240 (3) ◽  
pp. C91-C91 ◽  
Author(s):  
Ernest M. Wright
Keyword(s):  
Membrane Filter ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Kidney Cell Line ◽  
Cell Culture Model ◽  
Pig Kidney ◽  
Occluding Junctions ◽  
Culture Model ◽  
Continuous Sheet ◽  
Coated Membrane

Pig kidney cell line LLC-PK1 cultured on a collagen-coated membrane filter formed a continuous sheet of oriented asymmetrical epithelial cells joined by circumferential occluding junctions. In the presence of 5.5 mM D-glucose, a potential difference (PD) of 2.8 mV, apical bath negative, short-circuit current Isc of 13.2 microA . cm-2, and transepithelial resistance of 211 omega . cm2 were recorded. Isc and PD were reduced by phlorizin added to the apical bath but were unaffected when phlorizin was placed in the basolateral bath. Ouabain or the replacement of Na by tris-(hydroxymethyl)aminomethane or choline abolished the Isc. The sugar concentrations required to produce the half-maximal Isc were 0.13 mM beta-methyl-D-glucoside, 0.28 mM D-glucose, 0.65 mM alpha-methyl-D-glucoside, 0.77 mM 6-deoxy-D-glucose, 4.8 mM D-galactose, and 29 mM 3-O-methylglucose. When [Na] was reduced, the D-glucose required for half-maximal SCC increased. Isotopically 3H- and 14C-labeled D-glucose were used to determine simultaneous bidirectional fluxes; a resultant net apical-to-basolateral flux was present and could be abolished by phlorizin. The transported isotope cochromatographed with labeled D-glucose, indicating negligible metabolism. The cell culture model provides advantages for investigation of mechanisms of transepithelial glucose transport.

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