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This Article Full Text Full Text (PDF) All Versions of this Article: 297/4/F904    most recent 90685.2008v1 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 Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Liu, W. Articles by Satlin, L. M. PubMed PubMed Citation Articles by Liu, W. Articles by Satlin, L. M.

Mechanoregulation of BK channel activity in the mammalian cortical collecting duct: role of protein kinases A and C

¹Division of Pediatric Nephrology, Department of Pediatrics, Mount Sinai School of Medicine, New York; ; ²Department of Pharmacology, New York Medical College, Valhalla, New York; and ; ³Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania

Submitted November 16, 2008 ; accepted in final form August 4, 2009

Flow-stimulated net K secretion (J_K) in the cortical collecting duct (CCD) is mediated by an iberiotoxin (IBX)-sensitive BK channel, and requires an increase in intracellular Ca²⁺ concentration ([Ca²⁺]_i). The -subunit of the reconstituted BK channel is phosphorylated by PKA and PKC. To test whether the BK channel in the native CCD is regulated by these kinases, J_K and net Na absorption (J_Na) were measured at slow (1) and fast (5 nl·min^–1·mm^–1) flow rates in rabbit CCDs microperfused in the presence of mPKI, an inhibitor of PKA; calphostin C, which inhibits diacylglycerol binding proteins, including PKC; or bisindolylmaleimide (BIM) and Gö6976, inhibitors of classic and novel PKC isoforms, added to luminal (L) and/or basolateral (B) solutions. L but not B mPKI increased J_K in CCDs perfused at a slow flow rate; a subsequent increase in flow rate augmented J_K modestly. B mPKI alone or with L inhibitor abolished flow stimulation of J_K. Similarly, L calphostin C increased J_K in CCDs perfused at slow flow rates, as did calphostin C in both L and B solutions. The observation that IBX inhibited the L mPKI- and calphostin C-mediated increases in J_K at slow flow rates implicated the BK channel in this K flux, a notion suggested by patch-clamp analysis of principal cells. The kinase inhibited by calphostin C was not PKC as L and/or B BIM and Gö6976 failed to enhance J_K at the slow flow rate. However, addition of these PKC inhibitors to the B solution alone or with L inhibitor blocked flow stimulation of J_K. Interpretation of these results in light of the effects of these inhibitors on the flow-induced elevation of [Ca²⁺]_i suggests that the principal cell apical BK channel is tonically inhibited by PKA and that flow stimulation of J_K in the CCD is PKA and PKC dependent. The specific targets of the kinases remain to be identified.

K secretion; ROMK; mechanoregulation; in vitro microperfusion; laminar shear