Aldosterone stimulates K secretion prior to onset of Na absorption in guinea pig distal colon

1994 ◽  
Vol 266 (2) ◽  
pp. C552-C558 ◽  
Author(s):  
D. R. Halm ◽  
S. T. Halm
Keyword(s):  
Guinea Pig ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Ussing Chambers ◽  
High Affinity Receptor ◽  
Additive Increase ◽  
K Secretion ◽  
Affinity Receptor

Distal colon from guinea pig was stimulated in vitro by aldosterone in Ussing chambers that allowed measurement of short-circuit current (Isc) and tissue conductance (Gt). The response to aldosterone was delayed by approximately 20 min and resulted in a negative Isc, consistent with K secretion. Approximately 1 h later the Isc began to increase and eventually became positive, consistent with subsequent stimulation of Na absorption. The Na-absorptive response could be inhibited by mucosal amiloride without altering the rate of K secretion. Similarly, K secretion could be inhibited by serosal bumetanide without altering Na absorption. In the presence of spironolactone, actinomycin D, or cycloheximide, aldosterone failed to stimulate both K secretion and Na absorption. A dose response to aldosterone provided an apparent Kd of 2.6 +/- 0.5 nM, consistent with a high-affinity receptor coupled to this secretory response. Stimulation by the K secretagogue epinephrine did not produce an additive increase in K secretion, suggesting that the same cell type responds to both aldosterone and epinephrine and that the protein induced by aldosterone was not one of the membrane proteins responsible for K secretion.

scholarly journals Role of the BK channel (KCa1.1) during activation of electrogenic K+ secretion in guinea pig distal colon

2012 ◽  
Vol 303 (12) ◽  
pp. G1322-G1334 ◽  
Author(s):  
Jin Zhang ◽  
Susan T. Halm ◽  
Dan R. Halm
Keyword(s):  
Guinea Pig ◽  
Apical Membrane ◽  
Splice Variants ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Bk Channel ◽  
Prostaglandin E ◽  
Maximal Inhibition ◽  
K Secretion

Secretagogues acting at a variety of receptor types activate electrogenic K+ secretion in guinea pig distal colon, often accompanied by Cl− secretion. Distinct blockers of KCa1.1 (BK, Kcnma1), iberiotoxin (IbTx), and paxilline inhibited the negative short-circuit current ( Isc) associated with K+ secretion. Mucosal addition of IbTx inhibited epinephrine-activated Isc (epi Isc) and transepithelial conductance (epi Gt) consistent with K+ secretion occurring via apical membrane KCa1.1. The concentration dependence of IbTx inhibition of epi Isc yielded an IC50 of 193 nM, with a maximal inhibition of 51%. Similarly, IbTx inhibited epi Gt with an IC50 of 220 nM and maximal inhibition of 48%. Mucosally added paxilline (10 μM) inhibited epi Isc and epi Gt by ∼50%. IbTx and paxilline also inhibited Isc activated by mucosal ATP, supporting apical KCa1.1 as a requirement for this K+ secretagogue. Responses to IbTx and paxilline indicated that a component of K+ secretion occurred during activation of Cl− secretion by prostaglandin-E2 and cholinergic stimulation. Analysis of KCa1.1α mRNA expression in distal colonic epithelial cells indicated the presence of the ZERO splice variant and three splice variants for the COOH terminus. The presence of the regulatory β-subunits KCaβ1 and KCaβ4 also was demonstrated. Immunolocalization supported the presence of KCa1.1α in apical and basolateral membranes of surface and crypt cells. Together these results support a cellular mechanism for electrogenic K+ secretion involving apical membrane KCa1.1 during activation by several secretagogue types, but the observed K+ secretion likely required the activity of additional K+ channel types in the apical membrane.

Stimulation of Cl- and HCO3- secretion by intramural cholinergic neurons in guinea pig antrum in vitro

1993 ◽  
Vol 264 (1) ◽  
pp. G118-G125 ◽  
Author(s):  
A. G. Suzuki ◽  
J. Kameyama ◽  
M. Tsukamoto ◽  
K. Kaneko ◽  
Y. Suzuki
Keyword(s):  
Guinea Pig ◽  
Short Circuit ◽  
Cholinergic Neurons ◽  
Short Circuit Current ◽  
Muscarinic Agonist ◽  
Serosal Side ◽  
Ussing Chambers ◽  
Bethanechol Chloride ◽  
Stimulation Of

Regulation of Cl- and HCO3- secretion by intramural cholinergic neurons was investigated in guinea pig antrum in vitro. Sheet preparations composed of the mucosa and the submucosa were mounted between Ussing chambers and bathed with buffer-free solution on the luminal surface and with HCO3(-)-CO2 solution on the serosal side. Short-circuit current (Isc), unidirectional fluxes of 36Cl and 22Na, and the luminal alkalinization rate (JOHSL) were determined. Electrical stimulation of the preparations elicited increases in both JOHSL and Isc, which were inhibited by tetrodotoxin (TTX) and atropine. Physostigmine also evoked TTX- and atropine-sensitive increases in JOHSL and Isc. Similar increases in JOHSL and Isc were observed when the muscarinic agonist bethanechol chloride (BCh) was added to the serosal side. The responses to BCh were not affected by TTX. The BCh-induced increase in JOHSL was largely abolished by removal of HCO3- or Na+ and addition of ouabain (serosal side) but was neither sensitive to Cl- removal nor associated with 22Na secretion. The increase in Isc induced by BCh was associated with the increase in 36Cl secretion and was inhibited by removal of Cl- or Na+ and by addition of bumetanide or ouabain (both, serosal side). These results suggest that the submucosal cholinergic neurons are involved via muscarinic receptors in the stimulation of epithelial HCO3- and Cl- secretion. For both HCO3- and Cl-, the cellular and membrane mechanisms of secretion induced by muscarinic stimulation, although not entirely clear, appear to be different from those occurring under baseline conditions.

Potassium secretion by rabbit descending colon: effects of adrenergic stimuli

1986 ◽  
Vol 250 (4) ◽  
pp. G432-G439 ◽  
Author(s):  
P. L. Smith ◽  
R. D. McCabe
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Adrenergic Stimulation ◽  
Adrenergic Agents ◽  
Ussing Chambers ◽  
K Secretion ◽  
Potassium Secretion

Stripped rabbit distal colonic mucosa was studied in vitro in Ussing chambers to investigate the effects of adrenergic stimuli on Na+, K+, and Cl- transport. The adrenergic stimuli epinephrine and norepinephrine decrease short-circuit current in a dose-dependent manner, with a half-maximal effect at 5 X 10(-7) M and a maximal effect between 10(-5) and 10(-4) M. The effects produced by norepinephrine and epinephrine can also be elicited by the beta 1-agonist dobutamine, but not by the beta 2-agonist terbutaline or the alpha-agonist phenylephrine. In addition, the effects of adrenergic stimulation can be inhibited by the beta-antagonist propranolol but not by the muscarinic antagonist atropine, the alpha 2-antagonist yohimbine, or tetrodotoxin. The decrease in short-circuit current elicited by adrenergic stimuli is accompanied by an increase in net K+ secretion with no change in net Cl- or Na+ transport. This increase in net K+ secretion elicited by beta-adrenergic stimulation can be inhibited by trifluoperazine but not by indomethacin. These studies suggest that K+ transport by the colon can be regulated by adrenergic agents acting via beta 1-receptors.

Morphology and electrophysiology of guinea pig gastric mucosal repair in vitro

1983 ◽  
Vol 244 (2) ◽  
pp. G171-G182 ◽  
Author(s):  
M. J. Rutten ◽  
S. Ito
Keyword(s):  
Steady State ◽  
Guinea Pig ◽  
Morphological Analysis ◽  
Short Circuit ◽  
Isotonic Saline ◽  
Short Circuit Current ◽  
Electrical Parameters ◽  
Mucosal Repair ◽  
Ussing Chambers

Guinea pig gastric mucosae stripped of their outer muscle layers were studied in Ussing chambers for up to 14 h. Ten minutes after the mucosae were mounted in the chamber, the electrical parameters were low but continued to rise over 90 min until steady-state potential difference (PD), resistance (R), and short-circuit current (Isc) were recorded. Morphological analysis during the first 10 min of the tissue in the chamber revealed gaps in the epithelium due to damaged cells. However, tissues examined after 20 min in the chamber showed little evidence of epithelial discontinuity. Thereafter, the initial rise in the electrical parameters was noted. After steady-state attainment, the lumen was exposed to 1.25 M NaCl for 5 min and then changed back to 150 mM NaCl. Ten minutes after washout and return to control solutions, the PD, R, and Isc had fallen to low values. At 30 min after washout of the NaCl, the PD, R, and Isc began to increase and after 2 h were back to control values. Morphological analysis of mucosae fixed up to 10 min after exposure to 1.25 M NaCl showed extensive damage and exfoliation of surface cells. However, by 30 min the epithelium was restored and had very few discontinuities, which was then followed by the return of the electrical parameters. The conclusions from these studies are 1) guinea pig gastric mucosae exposed to hypertonic NaCl on the luminal side will primarily result in surface epithelial cell destruction with an immediate drop in the transepithelial electrical values; 2) after return to isotonic saline the damaged mucosa can repair itself within minutes, which then allows the reestablishment of the transepithelial electrical parameters by 2 h; and 3) the good viability and reproducibility of this preparation present a suitable mammalian model system for the study of factors of mucosal repair.

cGMP and Ca2+ regulation of ion transport across the isolated porcine distal colon epithelium

1994 ◽  
Vol 267 (4) ◽  
pp. R1026-R1033 ◽  
Author(s):  
M. D. DuVall ◽  
S. M. O'Grady
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Nacl Absorption ◽  
Flux Measurements ◽  
K Secretion ◽  
Baseline Values ◽  
Distal Colon Epithelium

Intact epithelium from the porcine distal colon was stripped of serosal muscle and mounted in Ussing chambers to investigate the regulation of Na, Cl, and K transport by guanosine 3',5'-cyclic monophosphate (cGMP) and elevations in intracellular [Ca2+]. Under voltage-clamped conditions cGMP (250 microM) produced an increase in tissue short-circuit current (Isc) that reached a maximal value within 10-20 min and remained elevated > 40 min. This response was associated with an inhibition of NaCl absorption and stimulation of Cl and K secretion. In the absence of Cl the Isc also slowly increased but returned to baseline values within 20 min. Bicarbonate removal from both serosal and mucosal solutions or serosal bumetanide (20 microM) reduced the effect of cGMP on Isc by approximately 40%. When performed simultaneously, these conditions reduced the cGMP response by approximately 60%. Transepithelial Na and Cl flux measurements indicated that serosal bumetanide blocked increased Cl secretion without effecting changes in NaCl absorption. In contrast, mucosal amiloride blocked the effects of cGMP on NaCl absorption but not Cl secretion. The cGMP Isc response was potentiated in the presence of 1 mM, but not 10 microM, amiloride. Moreover, 1 mM amiloride inhibited Isc under control conditions but was ineffective in the presence of cGMP. The Ca2+ ionophore ionomycin (3 microM) produced a transient increase in the Isc that was also associated with a decrease in transepithelial NaCl absorption and an increase in Cl and K secretion. In contrast to cGMP, the ionomycin Isc response was eliminated after Cl removal from the bath.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Prostanoids stimulate K secretion and Cl secretion in guinea pig distal colon via distinct pathways

2001 ◽  
Vol 281 (4) ◽  
pp. G984-G996 ◽  
Author(s):  
Dan R. Halm ◽  
Susan Troutman Halm
Keyword(s):  
Guinea Pig ◽  
Rank Order ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Prostanoid Receptors ◽  
Cl Secretion ◽  
Inflammatory Conditions ◽  
K Secretion

Short-circuit current ( I sc) and transepithelial conductance ( G t) were measured in guinea pig distal colonic mucosa isolated from submucosa and underlying muscle layers. Indomethacin (2 μM) and NS-398 (2 μM) were added to suppress endogenous production of prostanoids. Serosal addition of PGE2 (10 nM) stimulated negative I scconsistent with K secretion, and concentrations >30 nM stimulated positive I sc consistent with Cl secretion. PGE2 also stimulated G t at low and high concentrations. Dose responses to prostanoids specific for EP prostanoid receptors were consistent with stimulating K secretion through EP2 receptors, based on a rank order potency (from EC50 values) of PGE2 (1.9 nM) > 11-deoxy-PGE1 (8.3 nM) > 19( R)-hydroxy-PGE2 (13.9 nM) > butaprost (67 nM) > 17-phenyl-trinor-PGE2 (307 nM) ≫ sulprostone (>10 μM). An isoprostane, 8-iso-PGE2, stimulated K secretion with an EC50 of 33 nM. Cl secretory response was stimulated by PGD2 and BW-245C, a DP prostanoid receptor-specific agonist: BW-245C (15 nM) > PGD2 (30 nM) > PGE2 (203 nM). Agonists specific for FP, IP, and TP prostanoid receptors were ineffective in stimulating I sc and G t at concentrations <1 μM. These results indicate that PGE2stimulated electrogenic K secretion through activation of EP2 receptors and electrogenic KCl secretion through activation of DP receptors. Thus stimulation of Cl secretion in vivo would occur either via physiological concentrations of PGD2(<100 nM) or pathophysiological concentrations of PGE2(>100 nM) that could occur during inflammatory conditions.

Characterization of conductive pathways in guinea pig distal colon in vitro

1985 ◽  
Vol 248 (2) ◽  
pp. G176-G183 ◽  
Author(s):  
W. Clauss ◽  
J. Durr ◽  
G. Rechkemmer
Keyword(s):  
Guinea Pig ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Na Transport ◽  
Cl Transport ◽  
Intracellular Na Activity ◽  
In Vitro Investigation ◽  
The Individual

Isolated mucosal sheets of guinea pig distal colon were studied in vitro in Ussing-type chambers, using a computer-controlled voltage clamp. A conductance of 8–12 mS/cm2 and spontaneous variations of the potential difference (Vt, -4 to +6 mV) and the short-circuit current (Isc, -1.6 to +1.5 mu eq X cm-2 X h-1) were observed. With use of a green feed diet these variations could be entirely attributed to the rate of Na transport. Unidirectional Na and Cl fluxes were measured, and for Na, K, and Cl transport the individual conductances and directions were estimated from the changes in Vt and Isc, using the appropriate blockers amiloride, barium, and piretanide. The sum of the electrogenic Na, K, and Cl transport determines the spontaneous electrical behavior of this epithelium. Na transport was further characterized with transepithelial and transapical current-voltage relations. Apical Na entry occurred by diffusion, intracellular Na activity was 12 mM, and apical Na permeability was calculated as 0.02 cm/h. This study represents the first in vitro investigation of electrogenic transport in this epithelium and shows that it closely resembles transport mechanisms found in rabbit colon.

Protein kinase C potentiates cAMP-stimulated mouse duodenal mucosal bicarbonate secretion in vitro

2004 ◽  
Vol 286 (5) ◽  
pp. G814-G821 ◽  
Author(s):  
Bi-Guang Tuo ◽  
Jimmy Y. C. Chow ◽  
Kim E. Barrett ◽  
Jon I. Isenberg
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Duodenal Mucosa ◽  
Bicarbonate Secretion ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Ussing Chambers ◽  
Duodenal Bicarbonate Secretion

PKC has been shown to regulate epithelial Cl- secretion in a variety of models. However, the role of PKC in duodenal mucosal bicarbonate secretion is less clear. We aimed to investigate the role of PKC in regulation of duodenal mucosal bicarbonate secretion. Bicarbonate secretion by murine duodenal mucosa was examined in vitro in Ussing chambers using a pH-stat technique. PKC isoform expression and activity were assessed by Western blotting and in vitro kinase assays, respectively. PMA (an activator of PKC) alone had no effect on duodenal bicarbonate secretion or short-circuit current ( Isc). When PMA and dibutyryl-cAMP (db-cAMP) were added simultaneously, PMA failed to alter db-cAMP-stimulated duodenal bicarbonate secretion or Isc ( P > 0.05). However, a 1-h preincubation with PMA potentiated db-cAMP-stimulated duodenal bicarbonate secretion and Isc in a concentration-dependent manner (from 10-8 to 10-5M) ( P < 0.05). PMA preincubation had no effects on carbachol- or heat-stable toxin-stimulated bicarbonate secretion. Western blot analysis revealed that PKCα, -γ, -ϵ, -θ, -μ, and -ι/λ were expressed in murine duodenal mucosa. Ro 31–8220 (an inhibitor active against PKCϵ, -α, -β, and -γ), but not Gö 6983 (an inhibitor active against PKCα, -γ, -β, and -δ), reversed the potentiating effect of PMA on db-cAMP-stimulated bicarbonate secretion. PMA also time- and concentration-dependently increased the activity of PKCϵ, an effect that was prevented by Ro 31–8220 but not Gö 6983. These results demonstrate that activation of PKC potentiates cAMP-stimulated duodenal bicarbonate secretion, whereas it does not modify basal secretion. The effect of PKC on cAMP-stimulated bicarbonate secretion is mediated by the PKCϵ isoform.

Cellular pathways mediating tachykinin-evoked secretomotor responses in guinea pig ileum

1997 ◽  
Vol 273 (5) ◽  
pp. G1127-G1134 ◽  
Author(s):  
W. MacNaughton ◽  
B. Moore ◽  
S. Vanner
Keyword(s):  
Guinea Pig ◽  
Receptor Agonist ◽  
Short Circuit ◽  
Ussing Chamber ◽  
Short Circuit Current ◽  
Neurokinin A ◽  
Guinea Pig Ileum ◽  
Cellular Pathways ◽  
20 Nm

This study characterized tachykinin-evoked secretomotor responses in in vitro submucosal and mucosal-submucosal preparations of the guinea pig ileum using combined intracellular and Ussing chamber recording techniques. Superfusion of endogenous tachykinins substance P (SP), neurokinin A (NKA), and neurokinin B depolarized single submucosal neurons and evoked increased short-circuit current ( I sc) responses in Ussing chamber preparations. The NK1-receptor agonist [Sar9,Met(O2)11]SP [50% effective concentration (EC50) = 2 nM] depolarized all submucosal neurons examined. The NK3-receptor agonist senktide (EC50 = 20 nM) depolarized ∼50% of neurons examined, whereas the NK2-receptor agonist [Ala5,β-Ala8]NKA-(4—10) had no effect on membrane potential. [Sar9,Met(O2)11]SP and senktide evoked similar increases in I sc that were tetrodotoxin sensitive (91 and 100%, respectively) and were selectively blocked by the NK1antagonist CP-99,994 and the NK3antagonist SR-142801, respectively. Capsaicin-evoked increases in I sc were significantly inhibited (54%, P < 0.05) by CP-99,994 but not by SR-142801. Neither antagonist inhibited slow excitatory postsynaptic potentials. These findings suggest that tachykinin-evoked secretion in guinea pig ileum is mediated by NK1 and NK3 receptors on submucosal secretomotor neurons and that capsaicin-sensitive nerves release tachykinin(s) that activate the NK1 receptors.

Alterations in capsaicin-evoked electrolyte transport during the evolution of guinea pig TNBS ileitis

2002 ◽  
Vol 282 (6) ◽  
pp. G972-G980 ◽  
Author(s):  
Paula Miceli ◽  
Gerald P. Morris ◽  
Wallace K. MacNaughton ◽  
Stephen Vanner
Keyword(s):  
Substance P ◽  
Guinea Pig ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Electrolyte Transport ◽  
Secretory Function ◽  
Trinitrobenzenesulfonic Acid ◽  
Ussing Chambers ◽  
Circulating Cytokines

The efferent secretomotor activity of capsaicin-sensitive nerves was monitored during the evolution of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced ileitis in the guinea pig by recording changes in short-circuit current (Δ I sc) in response to capsaicin, substance P (SP), and carbachol. Submucosal-mucosal preparations mounted in standard Ussing chambers were studied at time 0, at 8 h, and 1, 3, 5, 7, 14, and 30 days following the intraluminal instillation of TNBS or saline. Maximal Δ I scresponses to capsaicin were dramatically attenuated (54%) by 24 h. By day 7, SP- and TTX-insensitive carbachol-stimulated Δ I sc were also significantly reduced. Similar attenuation in capsaicin and carbachol responses was observed in jejunal tissue 20 cm proximal to the inflamed site at day 7. These studies demonstrate that efferent secretomotor function of capsaicin-sensitive nerves is maintained early in TNBS ileitis but significantly reduced by 24 h. By day 7, defects in enterocyte secretory function at inflamed and noninflamed sites also occurred, an effect that may be mediated by circulating cytokines.

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