A Ca-dependent K channel in “luminal” membranes from the renal outer medulla

Burnham, Charles E.; Braw, Ruth H.; Karlish, Steven J. D.

doi:10.1007/bf01870809

Cited by 17 publications

(15 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2 show that approximately 40% of the total S6Rb+ uptake was inhibited by 2 mM BaCI2. This relatively prolonged uptake phase is consistent with the results of Burnham et al [3] and is typical of conductive K § transport when measured under these conditions…”

Section: Na+ Uptake Studiessupporting

confidence: 86%

See 1 more Smart Citation

Activation of K+ channels in renal medullary vesicles by cAMP-dependent protein kinase

Reeves¹,

McDonald²,

Mehta³

et al. 1989

J. Membrain Biol.

View full text Add to dashboard Cite

ADH, acting through cAMP, increases the potassium conductance of apical membranes of mouse medullary thick ascending limbs of Henle. The present studies tested whether exposure of renal medullary apical membranes in vitro to the catalytic subunit of cAMP-dependent protein kinase resulted in an increase in potassium conductance. Apical membrane vesicles prepared from rabbit outer renal medulla demonstrated bumetanide- and chloride-sensitive 22Na+ uptake and barium-sensitive, voltage-dependent 86Rb+ influx. When vesicles were loaded with purified catalytic subunit of cAMP-dependent protein kinase (150 mU/ml), 1 mM ATP, and 50 mM KCl, the barium-sensitive 86Rb+ influx increased from 361 +/- 138 to 528 +/- 120 pM/mg prot.30 sec (P less than 0.01). This increase was inhibited completely when heat-stable protein kinase inhibitor (1 microgram/ml) was also present in the vesicle solutions. The stimulation of 86Rb+ uptake by protein kinase required ATP rather than ADP. It also required opening of the vesicles by hypotonic shock, presumably to allow the kinase free access to the cytoplasmic face of the membranes. We conclude that cAMP-dependent protein kinase-mediated phosphorylation of apical membranes from the renal medulla increases the potassium conductance of these membranes. This mechanism may account for the ADH-mediated increase in potassium conductance in the mouse mTALH.

show abstract

Section: Na+ Uptake Studiessupporting

confidence: 86%

“…The conditions for ~'Rb + uptake were similar to those described by Burnham et al [3]. Specifically, we assayed Ba2+-sensitive ~Rb + uptake, which was ouabain-and bumetanide-insensitive in vesicles loaded, as described above, with I mM ATP.…”

Section: Procedures For Measuring S6rb+ Uptakementioning

confidence: 99%

Activation of K+ channels in renal medullary vesicles by cAMP-dependent protein kinase

Reeves¹,

McDonald²,

Mehta³

et al. 1989

J. Membrain Biol.

View full text Add to dashboard Cite

show abstract

“…The membrane vesicle preparation used in this study has been previously shown to be highly enriched in the basolateral marker Na+/K + ATPase (Jorgensen, 1974), as well as luminal TALH markers such as the Na~/K+/2C1 cotransporter and K + channel (Burnham et al, 1985;Burnham, Braw & Karlish, 1986;Klaerke et al, 1987). Analysis by sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that the 95 kilodalton c~-chain of the Na+/K + ATPase was by far the predominant protein band in the membrane preparation (not shown).…”

Section: Discussionmentioning

confidence: 91%

Characterization of chloride channels in membrane vesicles from the kidney outer medulla

Breuer

1989

J. Membrain Biol.

View full text Add to dashboard Cite

The basolateral membrane of the thick ascending loop of Henle (TALH) of the mammalian kidney is highly enriched in Na+/K+ ATPase and has been shown by electrophysiological methods to be highly conductive to Cl-. In order to study the Cl- conductive pathways, membrane vesicles were isolated from the TALH-containing region of the porcine kidney, the red outer medulla, and Cl- channel activity was determined by a 36Cl uptake assay where the uptake of the radioactive tracer is driven by the membrane potential (positive inside) generated by an outward Cl- gradient. The accumulation of 36Cl- inside the vesicles was found to be dependent on the intravesicular Cl- concentration and was abolished by clamping the membrane potential with valinomycin. The latter finding indicated the involvement of conductive pathways. Cl- channel activity was also observed using a fluorescent potential-sensitive carbocyanine dye, which detected a diffusion potential induced by an imposed inward Cl- gradient. The anion selectivity of the channels was Cl- greater than NO3- = I- much greater than gluconate. Among the Cl- transport inhibitors tested, 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPAB), 4,4'-diisothiocyano-stilbene-2,2'-disulfonate (DIDS), and diphenylamine-2-carboxylate (DPC) showed IC50 of 110, 200 and 550 microM, respectively. Inhibition of 36Cl uptake by NPPAB and two other structural analogues was fully reversible, whereas that by DIDS was not. The nonreactive analogue of DIDS, 4,4'-dinitrostilbene-2,2'-disulfonate (DNDS), was considerably less inhibitory than DIDS (25% inhibition at 200 microM). The irreversible inhibition by DIDS was prevented by NPPAB, whereas DPC was ineffective, consistent with its low inhibitory potency.(ABSTRACT TRUNCATED AT 250 WORDS)

show abstract

“…Wiener et al: Ca2+-Activated K* Channels mM MOPS-Tris, pH 7.2, at 20~ Furosemide (1 raM) was added to increase the sensitivity of the flux measurements by blocking the Na,K,Cl-cotransport system present in the colon epithelium [42]. In experiments where stimulatory effects of Ca 2+ were investigated, vesicles were preincubated for 30 rain in 3.75 mM EGTA and l0/~M CaX+-ionophore A23187 in order to deplete the vesicles of endogenous Ca 2+ [5,23]. The presence ofA23187 in the membrane ensures that the activities of Ca 2+ are the same inside and outside the membrane vesicles irrespective of their orientation.…”

Section: Reconstitution Of K + Channel Activitymentioning

confidence: 99%

Rabbit distal colon epithelium: III. Ca2+-activated K+ channels in basolateral plasma membrane vesicles of surface and crypt cells

1990

View full text Add to dashboard Cite

In the mammalian distal colon, the surface epithelium is responsible for electrolyte absorption, while the crypts are the site of secretion. This study examines the properties of electrical potential-driven 86Rb+ fluxes through K+ channels in basolateral membrane vesicles of surface and crypt cells of the rabbit distal colon epithelium. We show that Ba2(+)-sensitive, Ca2(+)-activated K+ channels are present in both surface and crypt cell derived vesicles with half-maximal activation at 5 x 10(-7) M free Ca2+. This suggests an important role of cytoplasmic Ca2+ in the regulation of the bidirectional ion fluxes in the colon epithelium. The properties of K+ channels in the surface cell membrane fraction differ from those of the channels in the crypt cell derived membranes. The peptide toxin apamin inhibits Ca2(+)-activated K+ channels exclusively in surface cell vesicles, while charybdotoxin inhibits predominantly in the crypt cell membrane fraction. Titrations with H+ and tetraethylammonium show that both high- and low-sensitive 86Rb+ flux components are present in surface cell vesicles, while the high-sensitive component is absent in the crypt cell membrane fraction. The Ba2(+)-sensitive, Ca2(+)-activated K+ channels can be solubilized in CHAPS and reconstituted into phospholipid vesicles. This is an essential step for further characterization of channel properties and for identification of the channel proteins in purification procedures.

show abstract

A Ca-dependent K channel in “luminal” membranes from the renal outer medulla

Cited by 17 publications

References 30 publications

Activation of K+ channels in renal medullary vesicles by cAMP-dependent protein kinase

Activation of K+ channels in renal medullary vesicles by cAMP-dependent protein kinase

Characterization of chloride channels in membrane vesicles from the kidney outer medulla

Rabbit distal colon epithelium: III. Ca2+-activated K+ channels in basolateral plasma membrane vesicles of surface and crypt cells

Contact Info

Product

Resources

About