Ca2+ activation and pH dependence of a maxi K+ channel from rabbit distal colon epithelium

1993 ◽  
Vol 136 (1) ◽  
Author(s):  
DanA. Klaerke ◽  
Hubert Wiener ◽  
Thomas Zeuthen ◽  
PeterL. J�rgensen
Keyword(s):  
Ph Dependence ◽  
Distal Colon ◽  
K Channel ◽  
Distal Colon Epithelium

Regulation of Ca 2+ -activated K + Channel from Rabbit Distal Colon Epithelium by Phosphorylation and Dephosphorylation

1996 ◽  
Vol 151 (1) ◽  
pp. 11-18 ◽  
Author(s):  
D.A. Klærke ◽  
H. Wiener ◽  
T. Zeuthen ◽  
P.L. Jørgensen
Keyword(s):  
Distal Colon ◽  
K Channel ◽  
Distal Colon Epithelium

Brain natriuretic peptide stimulates K and Cl secretion across porcine distal colon epithelium

1991 ◽  
Vol 260 (4) ◽  
pp. C750-C755 ◽  
Author(s):  
T. R. Traynor ◽  
S. M. O'Grady
Keyword(s):  
Brain Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Distal Colon ◽  
Ringer Solution ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
The Difference ◽  
Distal Colon Epithelium

Porcine distal colon epithelium was mounted in Ussing chambers and bathed with porcine Ringer solution. The serosal addition of brain natriuretic peptide (BNP; 50 nM) or atriopeptin III (AP-III; 500 nM) produced significant increases (50-75 microA/cm2) in short-circuit current (Isc). These increases in Isc were not inhibited by pretreatment with tetrodotoxin (TTX) or 5,8,11,14-eicosatetraynoic acid (ETYA). Analysis of concentration-response relationships revealed that BNP was 5.8-fold more potent than AP-III in stimulating the Isc. BNP and AP-III significantly increased the serosal-to-mucosal (S----M) Cl flux and reduced net Cl absorption by 38 and 41%, respectively. The BNP-stimulated S----M Cl flux was abolished when HCO3 was removed. In contrast, the vasoactive intestinal peptide (VIP)-stimulated S----M Cl flux was not affected by HCO3 replacement. In addition to their effects on Cl transport, BNP and AP-III increased net Rb secretion by 79 and 58%, respectively. BNP-stimulated Rb secretion was reduced by 76% after HCO3 replacement. These results indicate that natriuretic peptides stimulate K- and HCO3-dependent Cl secretion which is not present under basal conditions or after VIP stimulation. The difference in potency between BNP and AP-III suggests that ANP-B receptors may mediate their effects on ion transport in the porcine colon.

Comparison of aldosterone- and RU-28362-induced apical Na+ and K+ conductances in rat distal colon

1994 ◽  
Vol 267 (3) ◽  
pp. G485-G493 ◽  
Author(s):  
R. B. Lomax ◽  
G. I. Sandle
Keyword(s):  
Distal Colon ◽  
Distal Segment ◽  
K Channel ◽  
Rat Colon ◽  
Na Channel ◽  
Channel Blockers ◽  
Mineralocorticoid Antagonist ◽  
Channel Expression ◽  
K Secretion ◽  
Crypt Cells

In mammalian distal colon, aldosterone induces electrogenic Na+ absorption and electrogenic K+ secretion, whereas the sole transport effect of specific glucocorticoid agonists is thought to be stimulation of electroneutral NaCl absorption. In this study, intracellular microelectrodes and Na(+)- and K(+)-channel blockers were used to compare the effects of aldosterone and RU-28362 (a specific glucocorticoid agonist) on apical Na+ and K+ conductances in surface cells and upper crypt cells in the most distal colonic segment from adrenalectomized rats. In control animals, surface cells and crypt cells were devoid of apical Na+ and K+ conductances. In aldosterone-treated animals (70 micrograms.100 g body wt-1.day-1 for 7 days), Na+ conductances were induced in 88% of surface cells but only 40% of crypt cells, and the distribution of K+ conductances was similar (82% of surface cells and 50% of crypt cells). The same dose of RU-28362 also induced Na+ conductances in 82% of surface cells and 50% of crypt cells, which tended to be smaller than those induced by aldosterone. RU-28362, in contrast to aldosterone, had no effect on apical K+ conductance in surface cells or crypt cells. Concurrent treatment with the mineralocorticoid antagonist RU-28318 (3.5 mg.100 g body wt-1.day-1 for 7 days) inhibited Na(+)-channel expression in aldosterone-treated animals but had no effect in RU-28362-treated animals. We conclude that in the most distal segment of rat colon, aldosterone acts via mineralocorticoid receptors to induce apical Na+ and K+ conductances, which are only fully expressed in the surface cell population.(ABSTRACT TRUNCATED AT 250 WORDS)

Sign in / Sign up

Export Citation Format

Share Document