Anion Channels in the Apical Membrane of Collecting Duct Principal Cells in Culture

Abstract

Ion channels in the apical cell membrane of monolayers of rabbit renal collecting duct principal cells in primary culture were investigated with the patch-clamp technique. Besides three or more types of cation channels published previously, three types of anion channels were observed. Most frequent was an outwardly rectifying Cl^– selective channel with the slope conductance of 30.4 ± 4.8 pS (n = 6) in symmetrical isotonic NaCl solutions at 0 mV holding potential. This channel was only observed in excised patches. Its open probability was independent of the calcium concentration at the cytoplasmic surface of the membrane patch. The channel had complex open/close kinetics and was blocked by 5-nitro-2-(3-phenylpropylamino) benzoic acid from the extracellular surface. Inhibition increased at more cytoplasm-positive membrane potentials. Secondly, a high conductance, poorly selective anion channel was observed. It had a linear current voltage (I/V) relation with a conductance of 267 ± 46 pS (n = 4) and exhibited at least four substates. The open probability of this channel decreased sharply with increasing membrane potentials of either polarity. Thirdly, and least frequently, a bursting Cl^– selective channel was observed which displayed a peculiar I/V relation in isotonic NaCl solutions. Near 0 mV it had a slope conductance of ≈ 50 pS which increased to 113 ± 11 pS (n = 4) at potentials exceeding ± 50 mV. Since the peritubular cell membrane of principal cells is Cl^– permeable, it is conceivable that one or more of these channels contribute to collecting duct Cl^– absorption particularly in situations in which the luminal Cl^– concentration and the transepithelial potential difference are high.

PGE2 stimulates CI? secretion in murine M-1 cortical collecting duct cells in an autocrine manner

“…A recent study confirms that cAMP-stimulated fluid secretion occurs in microdissected rat inner medullary collecting duct segments and is inhibited by chloride channel blockers and the reduction of the extracellular Cl − concentration [58]. Patch-clamp evidence indicates several types of apical Cl − channels resident in collecting duct cells [11,35,39]. Moreover, intracellular Cl − activity in rabbit CCD principal cells is significantly elevated above electrochemical equilibrium [49,53], favouring Cl − secretion.…”

“…Total RNA was extracted using the Qiagen RNeasy Mini Kit according to the manufacturer's instructions and DNase I treated on the column to eliminate genomic DNA. cDNA was prepared from 1 μg of total RNA using M-MLV reverse transcriptase (GibcoBRL, UK) and poly (dT) [8][9][10][11][12] primers (Pharmacia, Germany). Controls for the RT procedure were also included.…”

Basolateral adrenoceptor activation mediates noradrenaline-induced Cl - secretion in M-1 mouse cortical collecting duct cells

“…However, active Clsecretion has been demonstrated in microdissected, microperfused rabbit CCD after the animals were fed a K + -rich diet [46]. There is also considerable evidence that various types of apical Cl -channels are present in CCD cells which may mediate Cl -secretion [6,26,28,42]. For Cl -secretion to occur a Cl -.…”

Cation Channels in the Apical Membrane of Collecting Duct Prinicipal Cell Epithelium in Culture

“…although single Na+ channels could not be resolved with certainty. Besides these cation channels also three types of CD channels have been observed, the experimental evi dence for which will be published separately [1]: an outwardly rectifying 32-pS Cl" channel, a bursting 120-pS Cl" channel and a voltageactivated. non-selective 300-pS anion channel.…”

“…This was based on a very small, though significant, hyperpolarization in re sponse to application of the CT channel block er 5-nitro-2-(3-phenylpropylamino)-benzoate [8]. Since the same blocker, if applied from the extracellular surface, also inhibited outwardly rectifying Cl" channels in the apical cell mem brane [1], we tend to conclude that this channel plays a role in Cl" absorption and hence thatcontrary to common belief -principal cells do participate in collecting duct Cl" transport. As in other cells, a physiological role of the non selective anion channel is difficult to envisage.…”