Inhibition of midgut ion transport by allatotropin (Mas-AT) and Manduca FLRFamides in the tobacco hornworm Manduca sexta.

1998 ◽  
Vol 201 (22) ◽  
pp. 3067-3074 ◽  
Author(s):  
K Y Lee ◽  
F M Horodyski ◽  
M E Chamberlin
Keyword(s):  
Ion Transport ◽  
Manduca Sexta ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Dependent Manner ◽  
Additive Effects ◽  
Maximal Inhibition ◽  
Posterior Midgut ◽  
Active Ion Transport ◽  
Dose Dependent

Short-circuit current (Isc) across the posterior midgut of day 2 fifth-instar tobacco hornworms (Manduca sexta) is inhibited by Manduca allatotropin (Mas-AT) and two Manduca FLRFamides (F7G and F7D). Another FLRFamide, F10, and the related molluscan tetrapeptide FMRFamide elicited only a modest inhibition of Isc. Mas-AT, F7G and F7D inhibited the Isc in a dose-dependent manner. Maximal inhibition of Isc by Mas-AT was achieved at a concentration of 50 nmol l-1. At 100 nmol l-1, Mas-AT produced a significantly greater inhibition of Isc than did F7G and F7D. The inhibition caused by Mas-AT was reversed by removing the peptide. Furthermore, the action of Mas-AT could be blocked by preabsorption with its antiserum. When F7G or F7D was added after the Isc had been inhibited by Mas-AT, a further reduction in the Isc was observed. No additive effects were seen when F7G and F7D were added together. In comparison with the anterior and middle regions, the posterior section of the midgut was the most sensitive to these three peptides. The Isc of midguts dissected from feeding fourth instars was inhibited by Mas-AT, F7D and F7G, whereas the Isc of midguts dissected from pharate fifth instars or wandering fifth instars was virtually unaffected by these peptides. Active ion transport across the posterior midgut of the silk moths Hyalophora cecropia and Bombyx mori was unaffected by these peptides.

Changes in midgut active ion transport and metabolism during larval-larval molting in the tobacco hornworm (Manduca sexta)

1997 ◽  
Vol 200 (3) ◽  
pp. 643-648 ◽  
Author(s):  
M Chamberlin ◽  
C Gibellato ◽  
R Noecker ◽  
E Dankoski
Keyword(s):  
Ion Transport ◽  
Manduca Sexta ◽  
Aerobic Capacity ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Tobacco Hornworm ◽  
Maximal Aerobic Capacity ◽  
Posterior Midgut ◽  
Molting Process ◽  
Active Ion Transport

Ion transport and metabolism in the posterior midgut before, during and after the molt to the fifth instar of the tobacco hornworm Manduca sexta were investigated. In situ measurements reveal that the transepithelial potential difference of the posterior midgut falls during the molting process. This finding was confirmed by in vitro experiments in which it was demonstrated that both the transepithelial potential and the short-circuit current are lower in molting fourth instars compared with feeding fourth instars. The short-circuit current increases after ecdysis, with a maximal rate being achieved approximately 4 h after the molt. Resumption of feeding after the molt is not necessary to initiate this increase in active ion transport. The metabolic organization of the tissue also changes during the molting process. The maximal activities of glycolytic enzymes and 3-hydroxyacyl-CoA dehydrogenase, an enzyme of lipid ss-oxidation, decrease during the molting process and increase after ecdysis. Although citrate synthase activity, an index of maximal aerobic capacity, decreases during the molt and increases again after ecdysis, tissue respiration is the same in feeding fourth instars and molting larvae. This result indicates that a greater percentage of maximal aerobic capacity is used during molting and that energy may be diverted to cell proliferation and differentiation and away from the support of active ion transport at this time.

Basolateral Cl− uptake mechanisms in Xenopus laevis lung epithelium

2010 ◽  
Vol 299 (1) ◽  
pp. R92-R100 ◽  
Author(s):  
Jens Berger ◽  
Martin Hardt ◽  
Wolfgang G. Clauss ◽  
Martin Fronius
Keyword(s):  
Xenopus Laevis ◽  
Ion Transport ◽  
Anion Exchanger ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Transport Processes ◽  
Lung Epithelium ◽  
Active Ion Transport ◽  
Uptake Mechanisms

A thin liquid layer covers the lungs of air-breathing vertebrates. Active ion transport processes via the pulmonary epithelial cells regulate the maintenance of this layer. This study focuses on basolateral Cl− uptake mechanisms in native lungs of Xenopus laevis and the involvement of the Na+/K+/2 Cl− cotransporter (NKCC) and HCO3−/Cl− anion exchanger (AE), in particular. Western blot analysis and immunofluorescence staining revealed the expression of the NKCC protein in the Xenopus lung. Ussing chamber experiments demonstrated that the NKCC inhibitors (bumetanide and furosemide) were ineffective at blocking the cotransporter under basal conditions, as well as under pharmacologically stimulated Cl−-secreting conditions (forskolin and chlorzoxazone application). However, functional evidence for the NKCC was detected by generating a transepithelial Cl− gradient. Further, we were interested in the involvement of the HCO3−/Cl− anion exchanger to transepithelial ion transport processes. Basolateral application of DIDS, an inhibitor of the AE, resulted in a significantly decreased the short-circuit current (ISC). The effect of DIDS was diminished by acetazolamide and reduced by increased external HCO3− concentrations. Cl− secretion induced by forskolin was decreased by DIDS, but this effect was abolished in the presence of HCO3−. These experiments indicate that the AE at least partially contributes to Cl− secretion. Taken together, our data show that in Xenopus lung epithelia, the AE, rather than the NKCC, is involved in basolateral Cl− uptake, which contrasts with the common model for Cl− secretion in pulmonary epithelia.

Effects of histamine and histamine receptor antagonists on ion transport in rabbit descending colon

1984 ◽  
Vol 247 (4) ◽  
pp. G411-G418 ◽  
Author(s):  
R. D. McCabe ◽  
P. L. Smith
Keyword(s):  
Ion Transport ◽  
Receptor Antagonist ◽  
Prostaglandin E1 ◽  
Short Circuit ◽  
Bathing Solution ◽  
Ionophore A23187 ◽  
Dependent Manner ◽  
H2 Receptor Antagonist ◽  
Maximal Inhibition ◽  
Descending Colon

The effects of histamine on colonic ion transport were examined in in vitro preparations of rabbit descending colon. Serosal addition of histamine (10(-5) M) produced a transient increase in short-circuit current (Isc) and transepithelial conductance. The Isc response to histamine could be blocked by removing Cl from both bathing solutions, adding furosemide (10(-3) M) to the serosal bathing solution, adding indomethacin to the serosal and mucosal bathing solutions (10(-5) M), or removing Ca from the serosal bathing solution. In addition, the histamine-induced increase in Isc was inhibited in a dose-dependent manner by the H1-receptor antagonist diphenhydramine, with a maximal inhibition at 10(-4) M and a half-maximal inhibition at 3 X 10(-7) M. The H2-receptor antagonist cimetidine (10(-3) M) was without effect on the histamine response. Measurement of unidirectional Na, K, and Cl fluxes revealed that serosal addition of diphenhydramine (10(-3) M) reduced basal Isc due to a decrease in mucosal-to-serosal Na flux. Serosal addition of diphenhydramine (10(-3) M) also inhibited the increase in Isc produced by serosal addition of prostaglandin E1, 8-bromo-cAMP, cholera toxin, or the ionophore A23187. Measurement of unidirectional K and Cl fluxes revealed that prostaglandin E1 alone increased serosal-to-mucosal K and Cl fluxes and reduced the mucosal-to-serosal K flux, thereby increasing net K and Cl secretion. Serosal diphenhydramine (10(-3) M) abolished the changes in Cl fluxes produced by prostaglandin E1 and reduced the magnitude of the changes in K fluxes.(ABSTRACT TRUNCATED AT 250 WORDS)

Bioelectric properties and ion flow across excised human bronchi

1984 ◽  
Vol 56 (4) ◽  
pp. 868-877 ◽  
Author(s):  
M. Knowles ◽  
G. Murray ◽  
J. Shallal ◽  
F. Askin ◽  
V. Ranga ◽  
...  
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Maximal Effect ◽  
Na Transport ◽  
Adrenergic Agents ◽  
Ion Flow ◽  
Cl Secretion ◽  
Active Ion Transport ◽  
Human Bronchi

Bioelectric properties and ion transport of excised human segmental/subsegmental bronchi were measured in specimens from 40 patients. Transepithelial electric potential difference (PD), short-circuit current (Isc), and conductance (G), averaged 5.8 mV (lumen negative), 51 microA X cm-2, and 9 mS X cm-2, respectively. Na+ was absorbed from lumen to interstitium under open- and short-circuit conditions. Cl- flows were symmetrical under short-circuit conditions. Isc was abolished by 10(-4) M ouabain. Amiloride inhibited Isc (the concentration necessary to achieve 50% of the maximal effect = 7 X 10(-7) M) and abolished net Na+ transport. PD and Isc were not reduced to zero by amiloride because a net Cl- secretion was induced that reflected a reduction in Cl- flow in the absorptive direction (Jm----sCl-). Acetylcholine (10(-4) M) induced an electrically silent, matched flow of Na+ (1.7 mueq X cm-1 X h-1) and Cl- (1.9 mueq X cm-12 X h-1) toward the lumen. This response was blocked by atropine. Phenylephrine (10(-5) M) did not affect bioelectric properties or unidirectional ion flows, whereas isoproterenol (10(-5) M) induced a small increase in Isc (10%) without changing net ion flows significantly. We conclude that 1) Na+ absorption is the major active ion transport across excised human bronchi, 2) Na+ absorption is both amiloride and ouabain sensitive, 3) Cl- secretion can be induced by inhibition of the entry of luminal Na+ into the epithelia, and 4) cholinergic more than adrenergic agents modulate basal ion flow, probably by affecting gland output.

Histamine stimulates ion transport by dog pancreatic duct epithelial cells through H1receptors

1998 ◽  
Vol 275 (1) ◽  
pp. G76-G84 ◽  
Author(s):  
Toan D. Nguyen ◽  
Charles N. Okolo ◽  
Mark W. Moody
Keyword(s):  
Epithelial Cells ◽  
Ion Transport ◽  
Receptor Antagonist ◽  
Pancreatic Duct ◽  
Direct Action ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Ussing Chambers

Histamine affects pancreatic secretion, but its direct action on ion transport by pancreatic duct epithelial cells (PDEC) has not been defined. We now characterize the secretory effects of histamine on cultured, well-differentiated, and nontransformed dog PDEC. Histamine stimulated, in a concentration-dependent manner (1–100 μM), a cellular125I−efflux that was inhibited by 500 μM 5-nitro-2-(3-phenylpropylamino)benzoic acid, 2.5 mM diphenylamine-2-carboxylate, and 500 μM DIDS and thus mediated through Ca2+-activated Cl− channels. Histamine-stimulated125I−efflux was 1) inhibited by 100 μM diphenhydramine, an H1receptor antagonist, 2) resistant to 1 mM cimetidine, an H2 receptor antagonist, 3) not reproduced by 1 mM dimaprit, an H2 agonist, and 4) inhibited by 50 μM 1,2-bis(2-aminophenoxy)ethane- N, N, N′, N′-tetraacetic acid-AM, a Ca2+ chelator, suggesting that it was mediated through H1 receptors acting via increased cytosolic Ca2+. Histamine also stimulated a86Rb+efflux that was sensitive to 100 nM charybdotoxin and thus mediated through Ca2+-activated K+ channels. When PDEC monolayers were studied in Ussing chambers, a short-circuit current of 21.7 ± 3.1 μA/cm2 was stimulated by 100 μM histamine. This effect was inhibited by diphenhydramine but not cimetidine, was not reproduced with dimaprit, and was observed only after serosal addition of histamine, suggesting that it was mediated by basolateral H1 receptors on PDEC. In conclusion, histamine, acting through basolateral H1 receptors, activates both Ca2+-activated Cl− and K+ channels; in this manner, it may regulate PDEC secretion in normal or inflamed pancreas.

Primary culture of duck salt gland. II. Neurohormonal stimulation of active transport

1985 ◽  
Vol 249 (1) ◽  
pp. C41-C47 ◽  
Author(s):  
R. J. Lowy ◽  
D. C. Dawson ◽  
S. A. Ernst
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Primary Cultures ◽  
Short Circuit Current ◽  
Salt Gland ◽  
Hormonal Control ◽  
Regulatory Control ◽  
Secretory Cells ◽  
Active Ion Transport ◽  
Secretory Transport

Primary cultures of structurally polarized sheets of avian salt gland secretory cells were mounted in Lucite chambers for transmural electrophysiological analysis. Transmural resistance values increased during the first 3 days of culture to 293 +/- 35 omega X cm2 and then decreased slowly thereafter. There was little short-circuit current (Isc) in the absence of secretagogues. Serosal addition of either carbachol or epinephrine resulted in a Isc consistent with positive charge flow from mucosa to serosa, thus demonstrating that these cell layers were capable of active ion transport in response to either cholinergic or adrenergic neurohormonal stimulation. Serosal ouabain or furosemide abolished the response to either agonist, while theophylline enhanced the response. Receptor specificity for the electrical responses was shown by selective inhibition of carbachol- and epinephrine-induced Isc by atropine and propranolol, respectively. The results demonstrate that these primary epithelial cell cultures are capable of active ion transport and are sensitive to known inhibitors of secretory transport, and suggest that intracellular coupling mechanisms for hormonal control are retained in culture. These cultures should be useful for studying mechanisms of ion secretory transport and their regulatory control.

Cadmium-induced Inhibition of ADH-stimulated Ion Transport in Cultured Kidney-derived Epithelial Cells (A6)

1997 ◽  
Vol 25 (3) ◽  
pp. 271-277
Author(s):  
Henning F. Bjerregaard ◽  
Brian Faurskov
Keyword(s):  
Epithelial Cells ◽  
Adenylate Cyclase ◽  
Ion Transport ◽  
Hormonal Regulation ◽  
Short Circuit ◽  
Distal Tubule ◽  
Short Circuit Current ◽  
Epithelial Cell Line ◽  
Active Ion Transport ◽  
Camp Metabolism

An epithelial cell line (A6) derived from the distal tubule of toad kidney, was used to study the effect of cadmium (Cd2+) on the increase in active ion transport induced by antidiuretic hormone (ADH). Addition of Cd2+ (1mM) to the basolateral solution of A6 epithelia generated an immediate and transient increase in active ion transport, measured as short circuit current (SCC). This increase was not affected by prior addition of ADH. However, there was a distinct inhibition of ADH-induced stimulation of SCC in epithelia pre-treated with Cd2+. Since cAMP serves as an intracellular messenger for ADH by increasing the ion permeability of the apical membrane in A6 epithelial cells, the effects of Cd2+ on enzymes involved in cAMP metabolism were measured. The results showed that Cd2+ markedly inhibits cAMP production by inhibiting adenylate cyclase (which had been stimulated with forskolin, magnesium or a non-hydrolysed GTP-analog), indicating that Cd2+ inhibits the catalytic subunit of adenylate cyclase. Furthermore, degradation of cAMP by phosphodiesterase was not stimulated by Cd2+, also suggesting that the mechanism by which Cd2+ inhibits the ADH-induced ion transport could be through inhibition of adenylate cyclase. Taken together, these results indicate that, in addition to the well-known toxic effect on the proximal tubule, Cd2+ could also have an effect on the distal part of the kidney, where the important hormonal regulation of salt and water homeostasis takes place.

Effects of raised osmolarity on canine tracheal epithelial ion transport function

1987 ◽  
Vol 62 (6) ◽  
pp. 2241-2245 ◽  
Author(s):  
J. R. Yankaskas ◽  
J. T. Gatzy ◽  
R. C. Boucher
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Upper Airway ◽  
Short Circuit Current ◽  
Base Line ◽  
Cl Secretion ◽  
Parallel Increase ◽  
Active Ion Transport ◽  
Solution Bathing ◽  
Surface Liquid

Evaporation of water from upper airway surfaces increases surface liquid osmolarity. We studied the effects of raised osmolarity of the solution bathing the luminal surface of excised canine tracheal epithelium. Osmolarity was increased by adding NaCl or mannitol. NaCl addition induced a concentration-dependent fall in short-circuit current and a rise in transepithelial conductance (-33% and +14% per 100 mosM, respectively). Unidirectional isotopic fluxes of 22Na, 36Cl, and [14C]mannitol were measured in short-circuited tissues in the base-line state and after addition of NaCl or mannitol to an isotonic mucosal solution. NaCl addition (75 mM) caused a 50% increase in conductance (G) and a parallel increase in [14C]mannitol permeability (Pmann), indicating an increase in paracellular permeability. Net Cl- secretion was reduced 50%, and net Na+ absorption was unchanged despite an increased chemical gradient for absorption, indicating an inhibition of active ion transport. Mannitol addition (150 mM) abolished net Na+ absorption but did not increase G or Pmann or change net Cl- secretion. These results suggest that responses to increased tracheal surface liquid osmolarity during spontaneous breathing may occur in both the cellular (inhibition of active Na+ and Cl- transport) and paracellular (increased [14C]mannitol permeability) compartments of the mucosa.

Fasting alters basal and stimulated ion transport in piglet jejunum

1994 ◽  
Vol 267 (1) ◽  
pp. R156-R163 ◽  
Author(s):  
H. V. Carey ◽  
U. L. Hayden ◽  
K. E. Tucker
Keyword(s):  
Ion Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Short Term ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Heat Stable ◽  
Active Ion Transport ◽  
Total Tissue ◽  
Net Fluxes

Three-week-old piglets were used to study the effects of short-term fasting on jejunal ion transport. A 48-h fast significantly reduced mucosal weight, villus height, and crypt depth. Fasting increased basal short-circuit current (Isc), which reflects active ion transport, and total tissue conductance (Gt) of muscle-stripped jejunal sheets mounted in Ussing chambers. Increases in Isc evoked by carbachol, serotonin, histamine, prostaglandin E2, or Escherichia coli heat-stable enterotoxin were significantly greater in the fasted piglets. Isc responses to mucosal D-glucose were also enhanced by the fast. Under basal conditions, unidirectional and net fluxes of Na+ and Cl-, as well as serosal-to-mucosal inulin fluxes, were significantly increased in fasted piglets. In fed piglets, carbachol increased net Cl- secretion by stimulating serosal-to-mucosal Cl- flux; Gt was not affected. In fasted piglets, carbachol increased net Cl- secretion by inhibiting mucosal-to-serosal fluxes with no effect on serosal-to-mucosal fluxes. In addition, carbachol significantly inhibited mucosal-to-serosal Na+ fluxes and reduced Gt in this group. Thus a 48-h fast increased unidirectional and net ion fluxes in piglet jejunum and enhanced ion transport responses to secretory agonists. The mechanism by which carbachol stimulated net Cl- secretion was also altered by the fast. These results suggest that the absence of luminal nutrition changes the ion transport characteristics of the jejunal epithelium.

Short-circuit current measurements in proximal tubule of Necturus kidney

1961 ◽  
Vol 201 (1) ◽  
pp. 157-163 ◽  
Author(s):  
Friedrich Wilhelm Eigler
Keyword(s):  
Ion Transport ◽  
Proximal Tubule ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Proper Position ◽  
Indifferent Electrode ◽  
Tubular Lumen ◽  
Active Ion Transport ◽  
Monovalent Ion

A modified short-circuit method, which requires only one pair of electrodes, was applied to the proximal tubule of the Necturus kidney for determination of the short-circuit current as a measure of active ion transport across the tubular wall. The indifferent electrode was placed on the surface of the exposed kidney and the tubular lumen was punctured with a microelectrode. After injection of oil into the glomerulus of the same nephron, a marked increase in electrical resistance between the electrodes during oil passage at the puncture site indicated the proper position of the electrode tip in the tubular lumen. The largest area effectively short-circuited (12.5 x 10–4 cm2) was determined by changing the position of two oil droplets between which measurements were made. Thirteen measurements of the short-circuit current in anesthetized normal Necturi averaged 4.8 x 10–6 amp/cm2, which corresponds to an active monovalent ion transport of 4.6 x 10–11 Eq/cm2 x sec.

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