HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 295/4/F1052    most recent 00031.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Nesterov, V. Articles by Korbmacher, C. Search for Related Content PubMed PubMed Citation Articles by Nesterov, V. Articles by Korbmacher, C.

Trypsin can activate the epithelial sodium channel (ENaC) in microdissected mouse distal nephron

¹Institut für Zelluläre und Molekulare Physiologie and ²Medizinische Klinik 4—Nephrologie und Hypertensiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany

Submitted 22 January 2008 ; accepted in final form 21 July 2008

Proteases are involved in the processing and activation of the epithelial sodium channel (ENaC). The aim of the present study was to investigate whether the prototypical serine protease trypsin can activate ENaC in microdissected, split-open mouse renal distal tubules. Whole-cell patch-clamp recordings from principal cells of connecting tubules (CNT) or cortical collecting ducts (CCD) demonstrated that addition of trypsin (20 µg/ml) to the bath solution increased the ENaC-mediated amiloride-sensitive whole cell current (I_Ami) in the majority of cells. In contrast, trypsin applied in the presence of an excess of soybean trypsin inhibitor had no stimulatory effect. The I_Ami response to trypsin was variable, ranging from no apparent effect to a twofold increase in I_Ami with an average stimulatory effect of 31 or 37% in mice on low-Na⁺ or standard Na⁺ diet, respectively. In cultured M-1 mouse collecting duct cells, a robust stimulatory effect of trypsin on I_Ami was only observed in cells pretreated with protease inhibitors. This suggests that endogenous proteases contribute to ENaC activation in renal tubular cells and that the degree of ENaC prestimulation by endogenous proteases determines the magnitude of the stimulatory response to exogenous trypsin. In conclusion, we provide electrophysiological evidence that trypsin can stimulate ENaC activity in native renal mouse tubules. Thus, in the kidney, ENaC stimulation by extracellular proteases may be a relevant regulatory mechanism in vivo.

microdissected renal tubules; whole-cell patch-clamp recording; serine proteases; epithelial sodium transport; amiloride