The essential role of luminal BK channels in distal colonic K+ secretion.
نویسندگان
چکیده
Distal colonic K(+) excretion is determined by the balance of K(+) absorption and K(+) secretion of the enterocytes. K(+) secretion occurs via active basolateral K(+) uptake mostly via the NKCC1 co-transporter followed by K(+) exit via a luminal K(+) channel. The specific focus here is directed towards the luminal secretory K(+) channel (1). Several recent observations highlight the pivotal role of the large conductance, Ca(2+)-activated K(Ca)1.1 (BK, KCNMA) channel as the only functionally relevant luminal K(+) efflux pathway in mouse distal colon (2, 3). This conclusion was based on defining results from BK knock-out mice. The following key observations were made: 1. BK channels mediate the resting distal colonic K(+) secretion (2, 4), 2. They are acutely stimulated by activation of luminal nucleotide receptor and elevations of intracellular Ca(2+) (2, 4, 5), 3. Colonic BK channels are up-regulated by increases of plasma aldosterone (3), 4. In addition, the cAMP-stimulated distal colonic K(+) secretion is apparently mediated via BK channels, 5. Finally, aldosterone was found to up-regulate specifically the ZERO (e.g. cAMP activated) C-terminal splice variant of the BK channel. In summary, we suggest that the sole exit pathway for transcellular (K+) secretion in mammalian distal colon is the BK channel, which is the target for short term intracellular Ca(2+) and cAMP activation and long term aldosterone regulation.
منابع مشابه
Distal colonic K(+) secretion occurs via BK channels.
K(+) secretion in the kidney and distal colon is a main determinant of K(+) homeostasis. This study investigated the identity of the relevant luminal secretory K(+) ion channel in distal colon. An Ussing chamber was used to measure ion transport in the recently generated BK channel-deficient (BK(-/-)) mice. BK(-/-) mice display a significant colonic epithelial phenotype with (1) lack of Ba(2+)-...
متن کاملControl of ion transport in mouse proximal and distal colon by prolactin.
The lactogenic hormone prolactin (PRL) has been known to affect Ca(2+) and electrolyte transport in the intestinal epithelium. In the present study we analyzed ion transport in mouse proximal and distal colon, and acute changes induced by PRL. In the proximal colon, carbachol activated a Ca(2+) dependent Cl(-) secretion that was sensitive to DIDS and NFA. In the distal colon, both ATP and carba...
متن کاملInvited Review BK channels in the kidney: role in K secretion and localization of molecular components
Pluznick, Jennifer L., and Steven C. Sansom. BK channels in the kidney: role in K secretion and localization of molecular components. Am J Physiol Renal Physiol 291: F517–F529, 2006; doi:10.1152/ajprenal.00118.2006.—Although it is generally accepted that ROMK is the K secretory channel in the mammalian distal nephron, recent in vitro and in vivo studies have provided evidence that largeconducta...
متن کاملBK channels in the kidney: role in K(+) secretion and localization of molecular components.
Although it is generally accepted that ROMK is the K(+) secretory channel in the mammalian distal nephron, recent in vitro and in vivo studies have provided evidence that large-conductance Ca(2+)-activated K(+) channels (BK, or maxi K) also secrete K(+) in renal tubules. This review assesses the current evidence relating BK channels with K(+) secretion. We shall consider the component proteins ...
متن کاملSegmental differences in upregulated apical potassium channels in mammalian colon during potassium adaptation
Rat proximal and distal colon are net K+ secretory and net K+ absorptive epithelia, respectively. Chronic dietary K+ loading increases net K+ secretion in the proximal colon and transforms net K+ absorption to net K+ secretion in the distal colon, but changes in apical K+ channel expression are unclear. We evaluated expression/activity of apical K+ (BK) channels in surface colonocytes in proxim...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- The journal of medical investigation : JMI
دوره 56 Suppl شماره
صفحات -
تاریخ انتشار 2009