title: Basolateral PAR-2 receptors mediate KCl secretion and inhibition of Na+ absorption in the mouse distal colon.
abstract: Proteinase-activated receptor-2 (PAR-2) may participate in epithelial ion transport regulation. Here we examined the effect of mouse activating peptide (mAP), a specific activator of PAR-2, on electrogenic transport of mouse distal colon using short-circuit current (I(SC)) measurements. Under steady-state conditions, apical application of amiloride (100 microM) revealed a positive I(SC) component of 74.3 +/- 6.8 microA x cm(-2) indicating the presence of Na+ absorption, while apical Ba2+ (10 mM) identified a negative I(SC) component of 26.2 +/- 1.8 microA x cm(-2) consistent with K+ secretion. Baseline Cl- secretion was minimal. Basolateral addition of 20 microM mAP produced a biphasic I(SC) response with an initial transient peak increase of 11.2 +/- 0.9 microA x cm(-2), followed by a sustained fall to a level 31.2 +/- 2.6 microA x cm(-2) (n = 43) below resting I(SC). The peak response was due to Cl- secretion as it was preserved in the presence of amiloride but was largely reduced in the presence of basolateral bumetanide (20 microM) or in the absence of extracellular Cl-. The secondary decline of I(SC) was also attenuated by bumetanide and by Ba2+, indicating that it is partly due to a stimulation of K+ secretion. In addition, the amiloride-sensitive I(SC) was slightly reduced by mAP, suggesting that inhibition of Na+ absorption also contributes to the I(SC) decline. Expression of PAR-2 in mouse distal colon was confirmed using RT-PCR and immunocytochemistry. We conclude that functional basolateral PAR-2 is present in mouse distal colon and that its activation stimulates Cl- and K+ secretion while inhibiting baseline Na+ absorption.
authors.affiliation: University Laboratory of Physiology, Oxford University, Parks Road, Oxford, OX1 3PT, UK.
authors.forename: John E
authors.initials: JE
authors.lastname: Cuffe
authors.forename: Marko
authors.initials: M
authors.lastname: Bertog
authors.forename: Sara
authors.initials: S
authors.lastname: Velázquez-Rocha
authors.forename: Olivier
authors.initials: O
authors.lastname: Dery
authors.forename: Nigel
authors.initials: N
authors.lastname: Bunnett
authors.forename: Christoph
authors.initials: C
authors.lastname: Korbmacher
mesh_terms: D000042:Absorption / Q000187:drug effects; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D002034:Bumetanide / Q000494:pharmacology; D002712:Chlorides / Q000502:physiology; D003106:Colon / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D004553:Electric Conductivity; D017615:Enteric Nervous System / Q000502:physiology; D007120:Immunochemistry / Q000379:methods; D007425:Intracellular Membranes / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009842:Oligopeptides / Q000494:pharmacology; D011189:Potassium Chloride / Q000378:metabolism*; D011453:Prostaglandins / Q000502:physiology; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin / Q000819:agonists / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012964:Sodium / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014357:Trypsin / Q000494:pharmacology
chemical_list: D002712:Chlorides; D009842:Oligopeptides; D011453:Prostaglandins; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin; C112356:seryl-leucyl-isoleucyl-glycyl--arginyl-leucinamide; D002034:Bumetanide; D001464:Barium; D011189:Potassium Chloride; D000584:Amiloride; D012964:Sodium; D014357:Trypsin