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J Teulon

Publications and source records attributed to J Teulon.

35 records · Page 2Linked to original sources
PubMed1992

Regulation by calcitonin of Na(+)-K(+)-Cl- cotransport in a rabbit thick ascending limb cell line.

The hormonal regulation of a Na(+)-K(+)-Cl- cotransport was investigated in a renal tubule cell line (RC.SV2 cells) transformed by the simian virus 40. This cell line has the main characteristics of cells from the thick ascending limb of Henle, including the presence of Tamm-Horsfall protein and stimulation of adenosine 3',5'-cyclic monophosphate (cAMP) production by calcitonin (CT). Kinetic studies with 22Na+, 36Cl-, and 86Rb+ indicated the existence of a Na(+)-K(+)-Cl- cotransport with a stoichiometry of 1Na+:1K+: 2Cl-. All compounds stimulating cAMP production enhanced the ouabain-resistant bumetanide-sensitive (Or-Bs) Rb+ influx mediated by Na(+)-K(+)-Cl- cotransport. CT (100 ng/ml) increased the Or-Bs influx twofold by enhancing maximum velocity without changing the apparent Michaelis constant. The K(+)-channel blocker barium blunted the CT-stimulated Or-Bs influx by 64-74%, whereas the Cl(-)-channel blocker 5-nitro-2-(3-phenylpropylamino)benzoate reduced the CT-stimulated influx by 28-40%. These results suggest that CT stimulates the Na(+)-K(+)-Cl- cotransport by a cAMP-dependent mechanism and that K+ recycling through K+ membrane channels is an important modulator of cotransporter-mediated ion fluxes.

Animals↗
PubMed1990

cAMP-activated chloride channel in the basolateral membrane of the thick ascending limb of the mouse kidney.

The properties of an anion-selective channel observed in basolateral membranes of microdissected, collagenase-treated, cortical thick ascending limbs of Henle's loop from mouse kidney were investigated using patch-clamp single-channel recording techniques. In basal conditions, single Cl- currents were detected in 8% of cell-attached and excised, inside-out, membrane patches whereas they were observed in 24% of cell-attached and 67% of inside-out membrane patches when tubular fragments were preincubated with Forskolin (10(-5) M) or 8-bromo-cAMP (10(-4) M) and isobutylmethylxanthine (10(-5) M). The channel exhibited a linear current-voltage relationship with conductances of about 40 pS in both cell-attached and cell-free membrane configurations. A PNa+/PCl- ratio of 0.05 was estimated in the presence of a 142/42 mM NaCl concentration gradient applied to inside-out membrane patches. Anionic selectivity of the channel followed the sequence Cl- greater than Br- greater than NO3- much greater than F-; gluconate was not a permeant species. The open-state probability of the channel increased with membrane depolarization in cell-attached, i.e., in situ membrane patches. In excised, inside-out, membrane patches, the channel was predominantly open with the open-state probability close to 0.8 over the whole range of potentials tested (-60 to +60 mV). The channel activity was not a function of internal calcium concentration between 10(-9) and 10(-3) M. We suggest that this Cl- channel, whose properties are distinct from those in other epithelia, could account for the well-documented conductance which mediates Cl- exit in the basolateral step of NaCl absorption in thick ascending limb of Henle's loop.

1-Methyl-3-isobutylxanthine↗
PubMed1989

A cation channel in the thick ascending limb of Henle's loop of the mouse kidney: inhibition by adenine nucleotides.

1. Patch-clamp single-channel current recordings were used to study the inhibition of Ca2+-activated non-selective cation channels by internal nucleotides in patches excised from basolateral membranes of the thick ascending limb of Henle's loop of the mouse kidney. 2. The application of ATP, ADP or AMP to the cytoplasmic face of excised inside-out membrane patches reduced the open-state probability of the channels (Po) in a dose-dependent way without effect upon the unitary current amplitude. Dose-response curves gave half-maximal inhibitory concentrations of 20, 21 and 2.5 microM for ATP, ADP and AMP, respectively, while the Hill coefficient was close to one in all three cases. 3. Cyclic AMP partially inhibited channel activity (Po = 35 +/- 17% of control) only at high, unphysiological concentrations (10(-3) M) while adenosine (10(-3) M) had very little effect (Po = 83 +/- 7% of control). 4. Replacement of adenine with other purines (guanine, hypoxanthine) or pyrimidine (uridine) bases very largely reduced inhibitory activity. Cyclic GMP had no effect. 5. Non-hydrolysable analogues of ATP, AMP-PNP (10(-3) M) and ATP-gamma-S (5 x 10(-4) M), were effective inhibitors of the channel (Po = 24 +/- 7 and 9 +/- 4% of control, respectively.

Adenine Nucleotides↗
PubMed1987

A Ca2-activated cation-selective channel in the basolateral membrane of the cortical thick ascending limb of Henle's loop of the mouse.

The patch-clamp technique was used to investigate the properties of a cation-selective channel in the basolateral membrane of microdissected collagenase-treated fragments of cortical thick ascending limbs of Henle's loop from mouse kidney. The channel activity was seldom observed in cell-attached patches (2 out 15 studied cases). In inside-out excised patches immersed in symmetrical NaCl Ringer's solutions, the unit channel conductance was ohmic and ranged from 22 to 33 pS (mean, 26.8 +/- 0.6 pS, n = 24). When NaCl was replaced by KCl (n = 8) or sodium gluconate (n = 2) on the cytoplasmic side of the membrane, single-channel currents still reversed at 0 mV and the conductance was unchanged. The reversal potential was +28.8 +/- 0.4 mV (n = 8) when a NaCl concentration (140 vs. 42 mmol/l) gradient was applied, close to the expected value (approx. 30 mV) for a cation selective channel. The channel was found to discriminate poorly between Na+, K+, Cs+, and Li+ ions. The activity of the channel was not clearly voltage-dependent but was dependent upon the free Ca2+ concentration on the cytoplasmic side of the membrane. We conclude that the channel resembles the non-selective cation channel which has been previously described in several tissues.

Animals↗
PubMed1985

Electrochemical profile of K+ and Na+ in the amphibian early distal tubule.

Double-barreled microelectrodes selective to either potassium or sodium were used to determine the transepithelial potential difference (VTE) and the intraluminal activity of potassium (alpha LuK) or sodium (alpha LuNa) in the early distal tubule (EDT) of Triturus waltlii in vivo; luminal activities were compared with the corresponding plasma ion activities, alpha PtK and alpha PtNa. The transepithelial equilibrium potentials for potassium (EK(TE] and sodium (ENa(TE] were computed from the respective transmural chemical distributions: they were used to assess the transepithelial electrochemical potential differences [(V-EK)TE and (V-ENa)TE]. By dividing the raw data into three groups of 30% total tubular length (0-30, 31-60, 61-90%), the following results were obtained. 1) VTE increases from +15 to +20 mV (lumen positive) between the first and second portion of the EDT but remains constant thereafter. 2) The alpha LuK/alpha PtK ratio decreases steadily along the EDT from 1.92 to 1.66 and then to 1.32. 3) The values of alpha LuNa/alpha PtNa in the same three subdivisions are 0.79, 0.44, and 0.45. 4) The (V-EK)TE difference is largely positive along the whole EDT: +32, +33, and +27 mV. 5) The (V-ENa)TE difference declines from +9 mV (first portion) to values statistically not different from zero in the last two thirds of the EDT.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

[Transport of chlorine in the proximal tubule. Its effects on water-electrolyte absorption].

Several studies in rat kidney have established that an appreciable fraction of proximal absorption is passive in nature and occurs across the highly conductive paracellular pathway. Passive absorption is generally ascribed to the transepithelial Cl- distribution, luminal Cl- activity (alpha lCl) being higher than plasma Cl- activity (alpha pCl). The inequality alpha lCl greater than alpha pCl generates a transepithelial diffusion potential, lumen positive, which taken together with the chemical potential differences of Cl- and Na+ across the epithelium gives rise to transepithelial electrochemical potential differences for Cl- and Na+ favoring their absorption. The alpha lCl greater than alpha pCl distribution is traditionally ascribed to preferential bicarbonate absorption. We argue that HCO3- absorption alone cannot generate a non equilibrium transepithelial Cl- distribution. Other mechanisms are necessary. Our measurements in amphibian proximal tubule demonstrate that the intracellular Cl- activity, alpha cCl, is higher than the theoretical value predicted for equilibrium. This distribution is the result of two basolateral coupled transport processes (Cl-/HCO3- exchange and Cl-/Na+ cotransport). It contributes to the exit of Cl- from cell to lumen (by passive diffusion and K+/Cl- cotransport), yielding alpha lCl values higher than the theoretical value for equilibrium with regard to plasma. Thus, a small transcellular flux of Cl- (without solvent) proceeds from interstitium to lumen. It compensates the dissipative tendency of a much higher paracellular Cl- absorptive flux (in association with water) on the transepithelial Cl- gradient. The result is a steady-state luminal Cl- distribution above equilibrium, along the major part of the proximal tubule.

Animals↗
PubMed1983

Peculiarities of the Na+/D-glucose cotransport system in Necturus renal tubules.

The effects of D-glucose addition to a glucose-free luminal perfusate were investigated in the proximal tubule of Necturus kidney, by electrophysiological techniques. The main findings are: (1) In the presence of sodium, D-glucose produces 10.5 mV +/- 1.1 (S.E.) depolarization. (2) Phlorizin reduces the magnitude of this response to 2.1 +/- 0.1 mV. (3) The glucose-evoked depolarization, delta VG, does not alter the intracellular K+ activity nor is it affected by peritubular addition of ouabain. (4) Isosmotic reduction of Na+ concentration in luminal perfusate from 95 to 2 mmol/l (choline or Li+ substituting for Na+) does not change the magnitude of delta VG; complete removal of sodium from the lumen lowers the value of delta VG (3.2 +/- 0.2 mV) but the response is not abolished. This observation suggests that the D-glucose carrier of renal tubules in Necturus is poorly specific with regard to the cotransported cation species.

Animals↗
PubMed1982

The electrical profile of the distal tubule in Triturus kidney.

The transepithelial potential difference (VTE) and transepithelial resistance (RTE) were determined along the length of the distal tubule of the amphibian Triturus alpestris. The site of impalements was determined at the end of each experiment by latex injection and microdissection. Two segments, differing by their distribution at the surface of the kidney, by their respective diameters and by their electrical properties could be identified: the early distal tubule (EDT) and the late distal tubule (LDT). VTE was invariably positive in the EDT; it increased from approximately + 5 mV to approximately + 22 mV within the first 30% of this segment and remained roughly constant distally to this site. RTE was estimated at 57 omega X cm2 in the EDT. The LDT exhibited essentially negative VTE figures with the exception of its very initial portion; the peak negativity at the end of the LDT was -35 mV. RTE was assessed from 8 measurements performed in the first 30% of the LDT; the tentative transepithelial resistance was 530 omega X cm2. Provisional evidence suggests that the transepithelial resistance of the terminal portion of the LDT may be substantially larger than the resistance measured in other parts of this segment.

Animals↗
PubMed1982

Proximal cell K+ activity: technical problems and dependence on plasma K+ concentration.

UNLABELLED: K+-selective liquid ion-exchanger double-barreled microelectrodes were used to measure intracellular K+ activity (alpha Ki) of proximal tubular cells in Necturus kidney. SEveral methodological problems inherent in the construction and in vivo application of such microelectrodes were considered, in particular the identification of leaky impalements and the correct assessment of alpha Ki during reversible perfusion of peritubular capillaries from control to a test solution. Peritubular potassium concentration (CpK) could be altered by means of double-barreled micropipettes containing a physiologic and a high or low K solution. The control alpha Ki value averaged 57.9 +/- 8.5 mM (mean +/- SD, n = 38) and the basolateral membrane potential was -70.4 +/- 5.8 mV. Thus, the K+ equilibrium potential across the basolateral membrane (EK) was -81.1 +/- 3.4 mV. Increasing CpK from 3.0 to 30.0 mM raised alpha Ki by 7.0 +/- 1.5 mM, and lowering CpK to 0.3 mM decreased alpha Ki by 9.2 +/- 2.9 mM. CONCLUSIONS: 1) the steady-state K+ distribution across the basolateral membrane indicates that potassium is actively pumped into the cell. 2) The relative stability of alpha Ki in the face of large CpK variations underscores the effectiveness of cell homeostasis; passive mechanisms appear to contribute to this end.

Animals↗
PubMed1981

The effects of barium on the electrical properties of the basolateral membrane in proximal tubule.

We studied the effects of millimolar Ba2+ concentrations on the properties of the basolateral membrane of the proximal tubule in Necturus kidney. Ba2+ was added in the peritubular perfusate by means of capillary microperfusion experiments. Basolateral membrane p.d. and conductance were continuously monitored in single tubules (their lumen was filled with oil) during reversible application of Ba2+ in peritubular fluid. The effect was membrane depolarization by 14mV and a decrease of membrane conductance to 63% of control values. This association strongly suggests that the main effect of Ba2+ is a decrease of the partial conductance to K+ at the basolateral membrane. However, in other experiments, performed also in oil-filled tubules, Ba2+ was shown to decrease intracellular K+ activity, recorded continuously by means of double-barreled (selective vs non selective) K+ microelectrodes. This and other, indirect evidence support the hypothesis that Ba2+ elicits also a small increase of the partial conductance to sodium at the basolateral membrane.

Animals↗
PubMed1980

Conductive properties of the proximal tubule in Necturus kidney.

The electrical properties of the proximal tubule of the in vivo Necturus kidney were investigated by injecting current (as rectangular waves) into the lumen or into the epithelium of single tubules and by studying the resulting changes of transepithelial (VL) and/or cell membrane potential (VC) at various distances from the source. In some experiments paired measurements of VL and VC were performed at two abscissas x and x'. The luminal length constant of about 1,030 micrometer was shown to provide a good estimate of the transepithelial resistance, specific resistance (RTE = 420 omega.cm2) and/or per unit length (rTE = 1.3 x 10(4) omega.cm). The apparent intraepithelial length constant was subject to distortions arising from concomitant current spread in the lumen. The resistances of luminal membrane (rL), basolateral membrane (rB), and shunt pathway (rS) were estimated by two independent methods at 3.5 x 10(4), 1.2 x 10(4), and 1.7 x 10(4) omega.cm, respectively. The corresponding specific resistances were close to 1,200, 600, and 600 omega.cm2. There are two main conclusions of this study. (a) The resistances of cell membranes and shunt pathway are of the same order of magnitude. The figure of the shunt resistance is at variance with the notion that the proximal tubule of Necturus is a leaky epithelium. (b) A rigorous assessment of the conductive properties of concentric cylindrical double cables (such as renal tubules) requires that electrical interactions arising from one cable to another be taken into account. Appropriate equations were developed to deal with this problem.

Animals↗
PubMed1978

The effect of a disulfonic acid stilbene on proximal cell membrane potential in Necturus kidney.

The effects of 0.5 mM 4-acetamido-4'-isothiocyano-stilbene-2,2' disulfonic acid on the electrical properties of the peritubular membrane were studied in the proximal tubule of the perfused Necturus kidney. The addition of stilbene isothiocyanate disulfonic acid in peritubular perfusate resulted in an average 4.5 mV hyperpolarization with no detectable changes of peritubular membrane input conductance. The depolarization elicited by high-K media was enhanced by 18% in the presence of stilbene isothiocyanate disulfonic acid, an observation indicating that the inhibitor increased the contribution of potassium to membrane potential, presumably by decreasing anionic permeabilities. The hyperpolarizing effect of stilbene isothiocyanate disulfonic acid was abolished when peritubular bicarbonate was removed from the medium and isoosmotically replaced by chloride. These data suggest that (a) intracellular bicarbonate activity is higher than that predicted from passive distribution, (b) stilbene isothiocyanate disulfonic acid decreases P HCO3, thus hyperpolarizing the membrane, (c) chloride distribution appears to be passive when bicarbonate is removed from the peritubular perfusate. The state of Cl distribution when extracellular bicarbonate is at physiologic concentration cannot be assessed from the present data.

Animals↗
PubMed1978

[Effects of salicylate on the electrical properties of the proximal convoluted tubule of Necturus maculosus].

The effects of peritubular salicylate for chloride substitution were studied in the isolated perfused Necturus kidney. This substitution resulted in changes of cell membrane p.d., varying from tubule to tubule; the withdrawal of the test-anion invariably produced a steep and prolonged depolarization. Exposure of the tissue to salicylate brought about, in addition, electrical uncoupling of junctional membranes, which was not related to concomitant changes of membrane p.d.

Animals↗
PubMed1976

Visual receptive field types in the nucleus dorsolateralis anterior of the pigeon's thalamus.

Extracellular recordings were made from cells in the dorsolateral thalamus (DLLv, DLLd, DLAmc) of the pigeon, and their receptive field properties analyzed with stationary and moving visual stimuli. One hundred and ten cells were classified as follows on the basis of their responses. I. On-center and off-center cells (56%). Most of the units in this class had a powerful inhibitory surround which decreased the activity generated at the field center and in some cases gave rise to firing when stimulated alone. II. On-off center cells (16%). These gave on-off responses to static stimulation. More than half of them had an inhibitory surround which suppressed both on and off discharge, or in other cases either the on or the off burst of the center response. This group of cells also responded strongly to motion independently of direction. III. Cells sensitive only to motion (28%). The discharges to movements of units in this class were not affected by the direction of motion. The visual properties of the thalamic units are discussed in conjunction with previous results in the optic tectum of the pigeon.

Animals↗