scholarly journals Collapse of ATP-Induced pH Gradient by Sodium Ions in Microsomal Membrane Vesicles Prepared from Atriplex gmelini Leaves

1989 ◽  
Vol 89 (1) ◽  
pp. 180-183 ◽  
Author(s):  
Tōru Matoh ◽  
Takayuki Ishikawa ◽  
Eiichi Takahashi
Keyword(s):  
Membrane Vesicles ◽  
Microsomal Membrane ◽  
Ph Gradient ◽  
Sodium Ions ◽  
Atriplex Gmelini

Cl-HCO3 and Cl-OH exchanges mediate Cl uptake in apical membrane vesicles of rat distal colon

1993 ◽  
Vol 264 (5) ◽  
pp. G874-G879 ◽  
Author(s):  
V. M. Rajendran ◽  
H. J. Binder
Keyword(s):  
Apical Membrane ◽  
Kinetic Constant ◽  
Membrane Vesicles ◽  
Distal Colon ◽  
Ph Gradient ◽  
Disulfonic Acid ◽  
Ph Homeostasis ◽  
Rat Distal Colon ◽  
Hyperbolic Curve ◽  
Apical Membrane Vesicles

This study describes Cl-HCO3 and Cl-OH exchanges as the mechanism for Cl uptake by apical membrane vesicles (AMV) of rat distal colon. Although HCO3 gradient-stimulated 36Cl uptake was additionally stimulated by the additional presence of a pH gradient, pH gradient-stimulated 36Cl uptake was not further enhanced by a HCO3 gradient. HCO3 gradient-stimulated and OH gradient-stimulated 36Cl uptake was not inhibited by voltage clamping, with K and its ionophore valinomycin, but was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, an anion exchange inhibitor, with an apparent inhibitory constant of 7.8 and 106.0 microM, respectively. Increasing intravesicular OH concentration in the absence of HCO3 (with fixed extravesicular Cl concentration) yielded a sigmoidal curve for 36Cl uptake. In contrast, increasing intravesicular OH concentration in the presence of equimolar intra- and extravesicular HCO3 (25 mM) yielded a saturable hyperbolic curve. Increasing extravesicular Cl concentration saturated both HCO3 gradient-stimulated and OH gradient-stimulated 36Cl uptake, with a kinetic constant for Cl of approximately 11.9 and 22.6 mM, respectively. We conclude that Cl uptake in AMV of rat distal colon occurs via two separate anion (Cl-HCO3 and Cl-OH) exchange processes. We speculate that one of these two anion exchanges may be responsible for transcellular Cl movement, while the other may be important in the regulation of intracellular pH homeostasis.

scholarly journals Mechanism of n-butyrate uptake in the human proximal colonic basolateral membranes

2002 ◽  
Vol 282 (4) ◽  
pp. G676-G682 ◽  
Author(s):  
S. Tyagi ◽  
J. Venugopalakrishnan ◽  
K. Ramaswamy ◽  
P. K. Dudeja
Keyword(s):  
Fatty Acid ◽  
Anion Exchange ◽  
Short Chain Fatty Acid ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Organ Donor ◽  
Chain Fatty Acid ◽  
Ph Gradient ◽  
Basolateral Membrane Vesicles ◽  
Exchange Inhibitor

Current studies were undertaken to characterize the mechanism of short-chain fatty acid (SCFA) transport in isolated human proximal colonic basolateral membrane vesicles (BLMV) utilizing a rapid-filtration n-[14C]butyrate uptake technique. Human colonic tissues were obtained from mucosal scrapings from organ donor proximal colons. Our results, consistent with the existence of a HCO[Formula: see text]/SCFA exchanger in these membranes, are summarized as follows: 1) n-[14C]butyrate influx was significantly stimulated into the vesicles in the presence of an outwardly directed HCO[Formula: see text] and an inwardly directed pH gradient; 2) n-[14C]butyrate uptake was markedly inhibited (∼40%) by anion exchange inhibitor niflumic acid (1 mM), but SITS and DIDS (5 mM) had no effect; 3) structural analogs e.g., acetate and propionate, significantly inhibited uptake of HCO[Formula: see text] and pH-gradient-driven n-[14C]butyrate; 4) n-[14C]butyrate uptake was saturable with a Kmfor butyrate of 17.5 ± 4.5 mM and a Vmaxof 20.9 ± 1.2 nmol · mg protein−1· 5 s−1; 5) n-[14C]butyrate influx into the vesicles demonstrated a transstimulation phenomenon; and 6) intravesicular or extravesicular Cl−did not alter the anion-stimulated n-[14C]butyrate uptake. Our results indicate the presence of a carrier-mediated HCO[Formula: see text]/SCFA exchanger on the human colonic basolateral membrane, which appears to be distinct from the previously described anion exchangers in the membranes of colonic epithelia.

K+-neutral amino acid symport of Bombyx mori larval midgut: a system operative in extreme conditions

1998 ◽  
Vol 274 (5) ◽  
pp. R1361-R1371 ◽  
Author(s):  
B. Giordana ◽  
M. G. Leonardi ◽  
M. Casartelli ◽  
P. Consonni ◽  
P. Parenti
Keyword(s):  
Amino Acid ◽  
Bombyx Mori ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Electrical Potential ◽  
Membrane Vesicles ◽  
Ph Gradient ◽  
Electrical Potential Difference ◽  
Posterior Midgut ◽  
Solution Bathing

The K+-dependent symporter for leucine and other neutral amino acids expressed along the midgut of the silkworm Bombyx mori operates with best efficiency in the presence of a steep pH gradient across the brush-border membrane, with external alkaline pH values up to 11, and an electrical potential difference (Δψ) of ∼200 mV. Careful determinations of leucine kinetics as a function of external amino acid concentrations between 50 and 1,000 μM, performed with brush-border membrane vesicles (BBMV) obtained from the middle and posterior midgut regions, revealed that the kinetic parameter affected by the presence of a ΔpH was the maximal rate of transport. The addition of Δψ caused a further marked increase of the translocation rate. At nonsaturating leucine concentrations in the solution bathing the external side of the brush-border membrane, leucine accumulation within BBMV and midgut cells was not only driven by the gradient of the driver cation K+ and Δψ but occurred also in the absence of K+. The ability of the symporter to translocate the substrate in its binary form allows the intracellular accumulation of leucine in the absence of K+, provided that a pH gradient, with alkaline outside, is present. The mechanisms involved in this accumulation are discussed.

pH gradient-stimulated phosphate transport in outer medullary brush-border membranes

1989 ◽  
Vol 257 (4) ◽  
pp. F639-F648
Author(s):  
G. A. Quamme ◽  
J. J. Walker ◽  
T. S. Yan
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Phosphate Uptake ◽  
Membrane Vesicles ◽  
Phosphate Transport ◽  
Brush Border Membrane Vesicles ◽  
Ph Gradient ◽  
Disulfonic Acid ◽  
Maximal Velocity ◽  
Medullary Tissue

Phosphate transport was studied in brush-border membrane vesicles prepared from outer medullary tissue of the porcine kidney. Phosphate uptake studies were performed in the absence of sodium at 21 degrees C. A 1.2- to 12-fold overshoot, above equilibrium values, was present with intracellular pH (pHin) equal to 8.0 and extracellular pH (pHout) equal to 6.5, which was not evident at pHin = pHout. Concentration-dependence of the pH-stimulate uptake was determined by the difference of uptake in the absence of a pH gradient (pHin = pHout) from that in the presence of a pH gradient over a large range of phosphate concentrations. The uptake was consistent with a single facilitative system characterized by apparent kinetic parameters; with Michaelis constant 149 +/- 11 microM and maximal velocity 4.9 +/- 0.4 nmol.mg protein-1.min-1, n = 3. Phosphate uptake was inhibited by the stilbene derivative 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid with a mean inhibition constant (Ki) value of 0.15 mM (n = 2). In addition, pH gradient-stimulated phosphate uptake was sensitive to furosemide and bumetanide; Ki values of 0.50 +/- 0.05 and 0.11 +/- 0.04 mM, respectively. Arsenate (1 mM) and phosphonoformate (1 mM) inhibited pH-dependent phosphate uptake, whereas sulfate (5 mM), bicarbonate (25 mM), and chloride (100 mM) were without effect, indicating that the transport system is relatively specific to phosphate and its close analogues. pH gradient-stimulated phosphate uptake was not influenced by potassium-diffusional gradients. The data provide evidence for a facilitative process in brush-border membrane vesicles isolated from outer medullary tissue of the pig kidney that is capable of transporting phosphate in the absence of sodium.

Transport of N1-methylnicotinamide by organic cation-proton exchange in rat liver membrane vesicles

1990 ◽  
Vol 259 (6) ◽  
pp. G973-G982
Author(s):  
R. H. Moseley ◽  
J. Morrissette ◽  
T. R. Johnson
Keyword(s):  
Substrate Specificity ◽  
Active Transport ◽  
Rat Liver ◽  
Time Course ◽  
Organic Cation ◽  
Drug Disposition ◽  
Membrane Vesicles ◽  
Proton Exchange ◽  
Ph Gradient ◽  
Transport Systems

The characteristics of hepatic organic cation transport were examined in basolateral (blLPM) and canalicular (cLPM) rat liver plasma membrane vesicles, using the naturally occurring organic cation, N1-methylnicotinamide (NMN). In blLPM vesicles, an outwardly directed H+ gradient (pHin 5.9/pHout 7.9) stimulated [3H]NMN uptake compared with [3H]NMN uptake under pH-equilibrated conditions. The time course of [3H]NMN uptake exhibited a transient "over-shoot" phenomenon, consistent with active transport. The proton ionophore, carbonyl cyanide-p-trifluoromethoxyphenylhydrazone, had no effect on [3H]NMN uptake, demonstrating that pH-dependent [3H]NMN uptake was not the result of a H+ diffusion potential. An outwardly directed H+ gradient also stimulated [3H]NMN uptake under voltage-clamped conditions, consistent with electroneutral NMN-H+ exchange. Under conditions that effectively dissipated the H+ gradient, no active transport of [3H]NMN was observed. In the absence of a pH gradient, the intravesicular presence of NMN trans-stimulated the uptake of [3H]NMN. NMN-H+ exchange was differentiated from sinusoidal Na(+)-H+ exchange by determining sensitivity to amiloride. The substrate specificity of NMN-H+ exchange in blLPM vesicles was examined by determining the cis-inhibitory effects of typical endogenous and exogenous substrates of other epithelial organic cation-H+ exchangers. Kinetic analysis of initial rates of carrier-mediated [3H]NMN uptake over a NMN concentration range of 0.05-15 mM demonstrated that uptake occurred via two saturable transport systems, one a high-affinity low-capacity process and the other a low-affinity high-capacity type. In contrast, in cLPM vesicles, no pH gradient-dependent [3H]NMN uptake was demonstrated. These findings are consistent with the presence of an organic cation-H+ antiport on the sinusoidal membrane, with features distinct from the renal antiport, such as substrate specificity and membrane localization, that may account for differences in drug disposition by these two organs.

Effects of cations on pH gradient-stimulated sulfate transport in rabbit ileal brush-border membrane vesicles

1985 ◽  
Vol 249 (5) ◽  
pp. G614-G621 ◽  
Author(s):  
C. M. Schron ◽  
R. G. Knickelbein ◽  
P. S. Aronson ◽  
J. Della Puca ◽  
J. W. Dobbins
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Electrical Potential ◽  
Membrane Vesicles ◽  
Disodium Salt ◽  
Brush Border Membrane Vesicles ◽  
Ph Gradient ◽  
Disulfonic Acid ◽  
Rabbit Ileum ◽  
External K

In brush-border membrane vesicles from rabbit ileum, we previously reported pH gradient-stimulated SO4 uptake and presented evidence that this represents carrier-mediated SO4-OH exchange. In the present study inhibitors of SO4-OH exchange (H-SO4 cotransport) were shown not to inhibit Na-SO4 cotransport, suggesting that these are two separate carrier-mediated transport mechanisms. While pH gradient-stimulated SO4 uptake was inhibited 87% by 0.1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, disodium salt (DIDS) and 79% by 1.0 mM furosemide, Na+-stimulated SO4 uptake was only inhibited 11 and 0%, respectively. K+ (20 mM), Cl (5 mM), and oxalate (0.25 mM) inhibited pH gradient-stimulated SO4 uptake (38-65%) but had no effect on Na+-stimulated SO4 uptake. Finally, at Na+ concentrations (10 mM) significantly less than that required for Na+-stimulated SO4 uptake (60-100 mM), external Na+ inhibited pH gradient-stimulated SO4 uptake, suggesting two independent effects of this cation. SO4 uptake was also inhibited by external K+ both in the presence and absence of a pH gradient. A Dixon plot of the DIDS-sensitive SO4 uptake under pH gradient conditions yielded a straight line, indicating a single site of interaction between external K+ and the SO4-OH carrier (apparent Ki = 7.2 mM). In contrast to the inhibition by external K+, internal K+ stimulated SO4 uptake. This effect was DIDS sensitive and not enhanced by valinomycin, suggesting an interaction of internal K+ with the SO4-OH exchanger independent of a K+-induced electrical potential. SO4 uptake and the effects of K+ were pH modulated with less SO4 uptake and less K+ effect at higher pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Multispecific anion exchange in basolateral (sinusoidal) rat liver plasma membrane vesicles

1986 ◽  
Vol 251 (5) ◽  
pp. G656-G664 ◽  
Author(s):  
G. Hugentobler ◽  
P. J. Meier
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Driving Forces ◽  
Competitive Inhibition ◽  
Membrane Vesicles ◽  
Ph Gradient ◽  
Disulfonic Acid ◽  
Sulfate Uptake ◽  
Plasma Membrane Vesicles ◽  
Liver Plasma Membrane

The mechanisms and driving forces for hepatic uptake of sulfate were investigated in basolateral (sinusoidal) rat liver plasma membrane vesicles. A transmembrane pH difference (pH 8.0 inside, 6.0 outside) stimulated sulfate uptake above equilibrium (“overshoot”). This pH gradient-stimulated sulfate uptake was saturable with increasing concentrations of sulfate and could be inhibited by probenecid, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), carbonyl cyanide p-(trifluoromethoxy)-phenylhydrazone, and nigericin. At low buffer concentrations and pH 6.0 an inwardly directed sodium gradient also stimulated sulfate uptake. This sodium-dependent sulfate uptake could be inhibited by amiloride and DIDS, indicating indirect coupling of sodium and sulfate flux through concomitant sodium-proton and sulfate-hydroxyl exchange. Cisinhibition of initial pH gradient-stimulated sulfate uptake, as well as transstimulation of sulfate uptake under pH-equilibrated conditions (pH 7.5 inside and outside), were observed with sulfate, thiosulfate, oxalate, and succinate, but not with chloride, bicarbonate, acetate, lactate, pyruvate, p-aminohippurate, citrate, glutamate, aspartate, and taurocholate. Furthermore, cholate and sulfobromophthalein exhibited competitive inhibition of pH gradient-stimulated sulfate uptake. In addition, an inside-to-outside hydroxyl gradient also stimulated uptake of cholate and this pH gradient-sensitive portion of cholate uptake was inhibited by extravesicular sulfate. In contrast to basolateral membranes, no evidence for multispecific sulfate-hydroxyl exchange was found in canalicular plasma membrane vesicles.

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