scholarly journals The protonmotive potential difference across the vacuo-lysosomal membrane of Hevea brasiliensis (rubber tree) and its modification by a membrane-bound adenosine triphosphatase

1981 ◽  
Vol 198 (2) ◽  
pp. 365-372 ◽  
Author(s):  
B Marin ◽  
M Marin-Lanza ◽  
E Komor
Keyword(s):  
Membrane Potential ◽  
Hevea Brasiliensis ◽  
Ph Dependence ◽  
Rubber Tree ◽  
Lysosomal Membrane ◽  
Potential Difference ◽  
Experimental Conditions ◽  
Carbonyl Cyanide ◽  
Membrane Bound ◽  
K Concentration

The vacuo-lysosomes of Hevea brasiliensis (rubber tree) constitute a suitable model system for the study of active transport and energization at the level of the membrane of plant vacuoles. The pH gradient (delta pH) and the membrane potential (delta psi) of vacuo-lysosomes were determined by means of the weak base methylamine and the lipophilic cation tetraphenylphosphonium. The values obtained depended strongly on the experimental conditions such as medium pH or K+ concentration. Under experimental conditions, i.e., pH 7.5 outside and low K+, the delta pH amounts to about 0.9 unit, interior acid, and the delta psi to -120 mV, interior negative. The delta psi is presumably caused by the imposed K+ gradient, and the internal acidification might be a consequence of the passive proton inflow along the electric field. This explanation is sustained by the ineffectiveness of carbonyl cyanide p-trifluoromethoxyphenylhydrazone in destroying the delta pH and delta psi, whereas higher K+ concentration decreased both. Under conditions existing in vivo, the membrane potential might be significantly lower. The presence of ATP increased the acidification of the intravesicular space by 0.5pH unit to a delta pH of up to 1.4 and shifts the membrane potential at least 60mV to a more positive value. The change of the protonmotive potential did not occur with ADP; the pH-dependence of the change was identical with the pH-dependence of a vacuo-lysosomal membrane-bound ATPase, and the effect of ATPase was prevented by the presence of the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone. The change of protonmotive potential difference, brought about by the ATPase, was at least 90 mV. This is evidence that a vacuo-lysosomal ATPase in plants can function as an electrogenic proton pump that transfers protons into the vacuo-lysosomal space.

scholarly journals Chloride-ion stimulation of the tonoplast H+-translocating ATPase from Hevea brasiliensis (rubber tree) latex. A dual mechanism

1985 ◽  
Vol 226 (1) ◽  
pp. 85-94 ◽  
Author(s):  
B P Marin ◽  
X Gidrol
Keyword(s):  
Membrane Potential ◽  
Atpase Activity ◽  
Hevea Brasiliensis ◽  
Rubber Tree ◽  
Electrical Potential ◽  
Chloride Ion ◽  
The Other ◽  
Potential Difference ◽  
Dual Mechanism ◽  
Stimulation Of

The effect of Cl- and other anions on the tonoplast H+-translocating ATPase (H+-ATPase) from Hevea brasiliensis (rubber tree) latex was investigated. Cl- and other anions stimulated the ATPase activity of tightly sealed vesicles prepared from Hevea tonoplast, with the following decreasing order of effectiveness: Cl- greater than Br- greater than SO4(2-) greater than NO3-. As indicated by the changes of the protonmotive potential difference, anion stimulation of tonoplast H+-ATPase was caused in part by the ability of these anions to dissipate the electrical potential. This interpretation assumes not a channelling of these anions against a membrane potential, negative-inside, but a modification of the permeability of these ions through the tonoplast membrane. In addition, Cl- and the other anions stimulated the ATPase activity solubilized from the tonoplast membrane. Consequently, the tonoplast H+-pumping ATPase can be considered as an anion-stimulated enzyme. These results are discussed in relation to various models described in the literature for the microsomal H+-ATPase systems claimed as tonoplast entities.

Relation of membrane potential to basolateral TEA transport in isolated snake proximal renal tubules

1995 ◽  
Vol 268 (6) ◽  
pp. R1539-R1545 ◽  
Author(s):  
Y. K. Kim ◽  
W. H. Dantzler
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Potent Inhibitor ◽  
Basolateral Membrane ◽  
Potential Difference ◽  
Renal Tubules ◽  
K Concentration ◽  
Electrochemical Equilibrium ◽  
Membrane Potential Difference ◽  
Basolateral Membrane Potential

We measured the effects of changes in bath K+ concentration ([K+]) on basolateral membrane potential difference (PD) and [3H]tetraethylammonium (TEA) transport in isolated snake (Thamnophis) proximal renal tubules (25 degrees C; pH 7.4). Increasing bath [K+] from 3 to 65 mM decreased PD from -60 mV (inside of cells negative) to -20 mV and 2-min uptake of [3H]TEA by approximately 25%, indicating that PD influences TEA entry into the cells. Uptake of [3H]TEA was inhibited similarly at both K+ concentrations by unlabeled TEA, indicating that uptake is carrier mediated. Kt (approximately 18 microM) for 2-min uptake of [3H]TEA in 3 mM K+ increased significantly in 65 mM K+, suggesting that the decrease in PD or the increase in [K+] alters the affinity of the transporter for TEA. The steady-state cell-to-bath ratio for [3H]TEA with 3 mM K+ (-60 mV PD) was approximately 16, significantly above the ratio of 10 predicted for passive distribution at electrochemical equilibrium. With 65 mM K+ (-20 mV PD) this ratio decreased to approximately 6, again significantly above the predicted ratio of 2. These data suggest that the PD can account for much, but not all, of the steady-state uptake of TEA. Efflux of [3H]TEA across the basolateral membrane was identical with either 3 or 65 mM K+ in the bath but was almost completely inhibited in either case by tetrapentylammonium, a potent inhibitor of TEA uptake. These data indicate that virtually all TEA transport across the basolateral membrane is carrier mediated and that transport out of the cells is unaffected by PD.

Nombres de Transport, tK, tNa et tca Pour la Membrane de la Cellule Hépatique In Vivo

1972 ◽  
Vol 50 (5) ◽  
pp. 416-422 ◽  
Author(s):  
Jean Pierre Caillé ◽  
O. F. Schanne
Keyword(s):  
Membrane Potential ◽  
Liver Cell ◽  
Ionic Mobility ◽  
Irreversible Thermodynamics ◽  
Transport Numbers ◽  
Experimental Conditions ◽  
External Potassium ◽  
K Concentration ◽  
External K

We measured the membrane potential of the liver cell in vivo at 38 °C as we increased the external potassium. For the range of K concentration from 20.4 to 78 mM, the membrane potential of the liver cell decreased with a slope of 20.2 mV per decade change in external K concentration. The tissue content of K, Na, and Cl was analyzed under the same experimental conditions. The cytoplasmic resistivity (111 ± 17.5 Ω-cm) was used as a criterion for the state of the ions in the cytoplasm. This result, when it is compared with the value predicted from the ionic content, suggests that either the ionic mobility or the ionic activity in the cytoplasm of the liver cell is less than in a simple salt solution. An analytical expression, derived with the use of irreversible thermodynamics, permits us to calculate the transport numbers for the ions K, Na, and Cl in the membrane of the liver cell (tK 0.28, tNa 0.12, tCl 0.61).

scholarly journals Co- and post-translational processing of the hevein preproprotein of latex of the rubber tree (Hevea brasiliensis)

1991 ◽  
Vol 266 (24) ◽  
pp. 15944-15948
Author(s):  
H.I. Lee ◽  
W.F. Broekaert ◽  
N.V. Raikhel ◽  
H. Lee
Keyword(s):  
Hevea Brasiliensis ◽  
Rubber Tree

scholarly journals Ethrel® stimulant increases the activity of soluble invertase isoforms in rubber tree (Hevea brasiliensis) bark tissues

2018 ◽  
Vol 12 (1) ◽  
pp. 99-107
Author(s):  
Débora Domiciano ◽  
◽  
Pollyanna Aparecida Carvalho ◽  
Luiz Edson Mota de Oliveira ◽  
Hilda Beatriz W. Cárdenaz ◽  
...  
Keyword(s):  
Hevea Brasiliensis ◽  
Rubber Tree

K+ transport across the lamprey erythrocyte membrane: characteristics of a Ba(2+)- and amiloride-sensitive pathway

1991 ◽  
Vol 159 (1) ◽  
pp. 303-324 ◽  
Author(s):  
K. Kirk
Keyword(s):  
Membrane Potential ◽  
Erythrocyte Membrane ◽  
Inhibitory Effect ◽  
Extracellular Ph ◽  
Transport Pathway ◽  
Full Effect ◽  
River Lamprey ◽  
K Concentration ◽  
86Rb Influx ◽  
K Transport

The characteristics of K+ transport in erythrocytes from the river lamprey (Lampetra fluviatilis) were investigated using standard radioisotope flux techniques. The cells were shown to have a ouabain-sensitive transport pathway that carried 43K+ and 86Rb+ into the cell at similar rates. Most of the ouabain-resistant 43K+ and 86Rb+ influx was via a pathway that was insensitive to cotransport inhibitors and to the replacement of extracellular Cl- or Na+. This pathway showed a strong selectivity for 43K+ over 86Rb+. It was inhibited fully by Ba2+ (I50 approximately 2.8 mumol l-1), amiloride (I50 approximately 150 mumol l-1) and ethylisopropylamiloride (I50 approximately 3.3 mumol l-1) and less effectively by quinine and by the tetraethylammonium ion. Inhibition by Ba2+ took full effect within a few minutes whereas the full inhibitory effect of amiloride took more than 1 h to develop. Experiments with the membrane potential probe [14C]tetraphenylphosphonium ion gave results consistent with the lamprey erythrocyte membrane having a Ba(2+)-sensitive K+ conductance that was significantly greater than the membrane Na+ conductance and which gave rise to a marked dependence of the membrane potential on the extracellular K+ concentration. The rate constants for Ba(2+)-sensitive 43K+ and 86Rb+ influx decreased (proportionally) with increasing extracellular K+ concentration in a manner that was consistent with the transport being via a conductive pathway. The decrease was attributed to a depolarisation of the membrane (in response to the increasing extracellular K+ concentration) and a consequent decrease in the driving force for the conductive movement of 43K+ and 86Rb+ into the cells. Ba(2+)-sensitive 86Rb+ influx increased significantly with decreasing cell volume and with increasing intracellular pH (at a constant extracellular pH) but increased only slightly with increasing extracellular pH. The pathway operated normally in the complete absence of extracellular Ca2+ but its activity decreased in cells pretreated with ionomycin and EGTA; this suggests a role for intracellular Ca2+ in the operation of the pathway.

Electrogenic Na+ Transport in a Crustacean Coxal Receptor

1979 ◽  
Vol 78 (1) ◽  
pp. 29-45
Author(s):  
MAURIZIO MIROLLI
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Input Resistance ◽  
Scylla Serrata ◽  
Partial Action ◽  
State Response ◽  
Electrogenic Na Pump ◽  
K Concentration ◽  
Low K ◽  
In Cells

1. The response of the coxal receptors of the crab Scylla serrata to step stretches consisted of a partial action potential, Vα, followed by a steady-state depolarization, V8. The input resistance of the fibre was reduced during V8. 2. In the absence of stimulation, the dendrites of the receptors depolarized when external Na+ was substituted with choline or Li+, and when the external K+ concentration was increased or decreased. The dendrites also depolarized when ouabain was added to the saline. 3. The amplitude of both Vα and V8 was dependent on external Na+. In cells which were depolarized by ouabain, the amplitude of V8 increased when the K+ concentration of the saline was reduced. 4. V8 was followed by a small, but long-lasting, after-potential which was depolarizing when the membrane potential was between −70 and −60 mV. In cells depolarized by ouabain or by low K+ saline, the after-potential became hyperpolarizing. 5. When trains of brief stretches (each 5 ms in duration) were used as stimuli, the cells responded with trains of Vα responses. During this tetanic stimulation the cells hyperpolarized; cessation of the stimulus train was followed by a long-lasting hyperpolarization (PTH). 6. PTH was abolished in Li+ saline, in low K+ saline, and in the presence of ouabain. In control or in low K+ saline, PTH was not accompanied by a decrease in the input resistance of the fibres. 7. It is concluded that an electrogenic Na+ pump (or equivalent process) contributes a substantial fraction of the membrane potential of the unstimulated coxal receptors. Pump activity could be increased by Na+-loading the distal part of the cells with trains of Vα responses. By contrast, during the steady-state response to stretch, the pump was not activated.

Characteristics of active Na transport in intact cardiac cells

1979 ◽  
Vol 236 (2) ◽  
pp. H189-H199 ◽  
Author(s):  
H. G. Glitsch
Keyword(s):  
Heart Muscle ◽  
Muscle Cells ◽  
Cardiac Cells ◽  
Na Transport ◽  
Concentration Gradients ◽  
Experimental Conditions ◽  
Na Pump ◽  
Na Efflux ◽  
Heart Muscle Cells ◽  
K Concentration

An active Na transport maintains the Na and K concentration gradients across the cell membrane of many cells and restores them following excitation. Heart muscle cells display frequent electrical discharges and thus the cardiac Na pump is of fundamental functional significance. Some methods for studying active Na transport are described. The active Na efflux from heart muscle cells is activated by an increase in the intracellular Na and the extracellular K concentration. The linkage between active Na efflux and active K influx varies widely according to the experimental conditions. The cardiac Na pump is electrogenic and can contribute directly to the membrane potential of the cells. The effects of active Na transport on contraction and intercellular coupling in myocardium are discussed.

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