Mechanisms of Na and Cl absorption across the distal colon epithelium of the pig

1992 ◽  
Vol 162 (1) ◽  
Author(s):  
TimothyR. Traynor ◽  
ScottM. O'Grady
Keyword(s):  
Distal Colon ◽  
Distal Colon Epithelium

Brain natriuretic peptide stimulates K and Cl secretion across porcine distal colon epithelium

1991 ◽  
Vol 260 (4) ◽  
pp. C750-C755 ◽  
Author(s):  
T. R. Traynor ◽  
S. M. O'Grady
Keyword(s):  
Brain Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Ringer Solution ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
The Difference ◽  
Distal Colon Epithelium

Porcine distal colon epithelium was mounted in Ussing chambers and bathed with porcine Ringer solution. The serosal addition of brain natriuretic peptide (BNP; 50 nM) or atriopeptin III (AP-III; 500 nM) produced significant increases (50-75 microA/cm2) in short-circuit current (Isc). These increases in Isc were not inhibited by pretreatment with tetrodotoxin (TTX) or 5,8,11,14-eicosatetraynoic acid (ETYA). Analysis of concentration-response relationships revealed that BNP was 5.8-fold more potent than AP-III in stimulating the Isc. BNP and AP-III significantly increased the serosal-to-mucosal (S----M) Cl flux and reduced net Cl absorption by 38 and 41%, respectively. The BNP-stimulated S----M Cl flux was abolished when HCO3 was removed. In contrast, the vasoactive intestinal peptide (VIP)-stimulated S----M Cl flux was not affected by HCO3 replacement. In addition to their effects on Cl transport, BNP and AP-III increased net Rb secretion by 79 and 58%, respectively. BNP-stimulated Rb secretion was reduced by 76% after HCO3 replacement. These results indicate that natriuretic peptides stimulate K- and HCO3-dependent Cl secretion which is not present under basal conditions or after VIP stimulation. The difference in potency between BNP and AP-III suggests that ANP-B receptors may mediate their effects on ion transport in the porcine colon.

Regulation of colonic ion transport by GRP. II. GRP modulates the epithelial response to PGE2

1996 ◽  
Vol 270 (3) ◽  
pp. C859-C865 ◽  
Author(s):  
T. R. Traynor ◽  
S. M. O'Grady
Keyword(s):  
Time Course ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Electrolyte Transport ◽  
Gastrin Releasing Peptide ◽  
Transcellular Pathway ◽  
Flux Measurements ◽  
Pg E2 ◽  
Distal Colon Epithelium

The purpose of this study was to examine the potential modulatory effects of gastrin-releasing peptide (GRP) on prostaglandin (PG) E2-stimulated electrolyte transport across the distal colon epithelium. In an earlier study, PGE2 was shown to reduce net Cl absorption without altering the serosal-to-mucosal unidirectional Cl flux in porcine distal colon (19). In the present study, tissues were pretreated with serosal or mucosal GRP and subsequently stimulated with PGE2. The resulting increase in short-circuit current (ISC) was 152% (serosal GRP) and 49% (mucosal GRP) greater than control PGE2 responses alone. Serosal, but not mucosal, GRP also enhanced the ISC response to vasoactive intestinal peptide. On the basis of flux measurements, the combined effects of serosal GRP and PGE2 resulted in the activation of a transcellular pathway for Cl secretion, which was not activated by either mediator alone. The time course of the PGE2 response was also affected by GRP. Serosal GRP shortened the time to maximum ISC by 35%, whereas mucosal peptide lengthened the time to maximum ISC by 68% These results suggest that GRP acts as a modulator of PG action on electrolyte transport in the distal colon.

scholarly journals Heterogeneous nuclear ribonucleoprotein A2/B1 is a novel aldosterone target gene in the rat distal colon epithelium

2013 ◽  
Vol 27 (S1) ◽  
Author(s):  
Diego Alvarez Rosa ◽  
Ivan Hernandez‐Diaz ◽  
Silvia Morales ◽  
Guadalberto Hernandez ◽  
Eduardo Salido ◽  
...  
Keyword(s):  
Target Gene ◽  
Distal Colon ◽  
Heterogeneous Nuclear Ribonucleoprotein ◽  
Rat Distal Colon ◽  
Distal Colon Epithelium ◽  
Nuclear Ribonucleoprotein

scholarly journals Quantification and distribution of Ca2+-activated maxi K+ channels in rabbit distal colon

1999 ◽  
Vol 277 (1) ◽  
pp. G22-G30 ◽  
Author(s):  
Morten Grunnet ◽  
Hans-Günther Knaus ◽  
Christina Solander ◽  
Dan A. Klaerke
Keyword(s):  
Plasma Membranes ◽  
Distal Colon ◽  
Channel Activity ◽  
Functional Studies ◽  
Receptor Concentration ◽  
Flux Measurements ◽  
Distal Colon Epithelium ◽  
Equilibrium Dissociation ◽  
Channel Type ◽  
Stimulation Of

The Ca2+-activated maxi K+ channel is an abundant channel type in the distal colon epithelium, but nothing is known regarding the actual number and precise localization of these channels. The aim of this study has therefore been to quantify the maxi K+ channels in colon epithelium by binding of iberiotoxin (IbTX), a selective peptidyl ligand for maxi K+ channels. In isotope flux measurements 75% of the total K+ channel activity in plasma membranes from distal colon epithelium is inhibited by IbTX ( K 0.5 = 4.5 pM), indicating that the maxi K+ channel is the predominant channel type in this epithelium. Consistent with the functional studies, the radiolabeled double mutant 125I-IbTX-D19Y/Y36F binds to the colon epithelium membranes with an equilibrium dissociation constant of ∼10 pM. The maximum receptor concentration values (in fmol/mg protein) for125I-IbTX-D19Y/Y36F binding to colon epithelium are 78 for surface membranes and 8 for crypt membranes, suggesting that the maxi K+ channels are predominantly expressed in the Na+-absorbing surface cells, as compared with the Cl−-secreting crypt cells. However, aldosterone stimulation of this tissue induced by a low-Na+ diet does not change the total number of maxi K+ channels.

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)

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