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Role of vasopressin in rat distal colon function
Author(s) -
Cristià Esther,
Amat Concepció,
Naftalin Richard J.,
Moretó Miquel
Publication year - 2007
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2006.118315
Subject(s) - vasopressin , crypt , medicine , endocrinology , chemistry , receptor , biology
The specific role of vasopressin in colonic crypt function and its possible synergistic action with aldosterone were studied. Sprague‐Dawley rats fed a high‐Na + (HS; 150 m m NaCl) or a low‐Na + (LS; 150 μ m NaCl) diet were deprived of water or infused with vasopressin, and some animals were treated with specific vasopressin receptor subtype V 1 and V 2 antagonists. The expression of the epithelial Na + channel (ENaC), α‐smooth muscle actin (α‐SMA) and aquaporin‐2 (AQP‐2) were determined by immunolocalization in distal colonic mucosa. The pericryptal Na + concentration was determined by confocal microscopy, using a low‐affinity Na + ‐sensitive fluorescent dye (sodium red) and crypt permeability was measured by the rate of escape of fluorescein isothiocyanate‐labelled dextran (10 kDa) from the crypt lumen into the pericryptal space in isolated rat distal colonic mucosa. A high plasma concentration of vasopressin raised α‐SMA expression in the pericryptal sheath ( P < 0.05), increased the pericryptal Na + accumulation in this space ( P < 0.01) and caused a reduction of crypt wall permeability ( P < 0.01). All these effects were reversed by selective blockade of V 1 and V 2 receptors. No synergistic effects with aldosterone were observed. Dehydration and vasopressin infusion increased AQP‐2 expression in distal colonic mucosa ( P < 0.05). This action of vasopressin was prevented by tolvaptan, a specific V 2 receptor antagonist ( P < 0.05). It is concluded that vasopressin has trophic effects in the rat distal colon, increasing pericryptal myofibroblast growth which affects crypt absorption, and these effects are independent of the presence of aldosterone.