POSTNATAL DEVELOPMENT OF ORGANIC CATION TRANSPORT IN THE RAT LIVER

1998 ◽  
Vol 37 (2) ◽  
pp. 131-136 ◽  
Author(s):  
F. MARTEL ◽  
M.J. MARTINS ◽  
C. CALHAU ◽  
C. HIPÓLITO-REIS ◽  
I. AZEVEDO
Keyword(s):  
Postnatal Development ◽  
Rat Liver ◽  
Organic Cation ◽  
Cation Transport ◽  
Organic Cation Transport

Organic cation transport by rat liver lysosomes

1995 ◽  
Vol 268 (3) ◽  
pp. G480-G486 ◽  
Author(s):  
R. H. Moseley ◽  
R. W. Van Dyke
Keyword(s):  
Steady State ◽  
Membrane Potential ◽  
Rat Liver ◽  
Organic Cation ◽  
Cation Transport ◽  
Transport Processes ◽  
Organic Cation Transport ◽  
Cationic Drugs ◽  
Liver Lysosomes ◽  
Rat Liver Lysosomes

Hepatic organic cation transport has been characterized in rat liver plasma membrane vesicles, using the quaternary amine tetraethylammonium (TEA) as a model substrate. Sinusoidal TEA uptake is stimulated by an inside-negative membrane potential; TEA transport across the canalicular membrane is mediated by electroneutral organic cation-H+ exchange. Substrates for these transport processes include procainamide ethobromide (PAEB) and vecuronium, cationic drugs that undergo biliary excretion. Given the apparent absence of sinusoidal transport mechanisms able to generate high hepatocyte-to-blood organic cation concentration ratios, intracellular transport of organic cations may involve sequestration and concentration within acidified organelles. Therefore, the characteristics of TEA uptake were examined in isolated rat liver lysosomes that are acidified by a well-described H(+)-adenosinetriphosphatase (ATPase). Lysosomal uptake of [14C]TEA was a time- and ATP-dependent process, reaching steady state after 30-60 min. Steady-state [14C]TEA uptake was significantly reduced by omission of ATP and by addition of monensin, conditions that alter lysosomal pH and membrane potential gradients, and by the H(+)-ATPase inhibitors, N-ethylmaleimide and bafilomycin A. ATP-dependent lysosomal [14C]TEA uptake was significantly inhibited by PAEB, vecuronium, and other organic cationic substrates of canalicular TEA/H+ exchange. These findings demonstrate that rat liver lysosomes sequester certain organic cationic drugs, most likely via organic cation/H+ exchange driven by H(+)-ATPase. Canalicular organic cation/H+ exchange may reflect, in part, the exocytic insertion of this transporter from an intracellular compartment to this membrane domain.

Organic cation transport by rat liver plasma membrane vesicles: studies with tetraethylammonium

1992 ◽  
Vol 263 (5) ◽  
pp. G775-G785 ◽  
Author(s):  
R. H. Moseley ◽  
S. M. Jarose ◽  
P. Permoad
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Organic Cation ◽  
Membrane Vesicles ◽  
Cation Transport ◽  
Organic Cations ◽  
Organic Cation Transport ◽  
Plasma Membrane Vesicles ◽  
Canalicular Membrane ◽  
Ph Dependent

Recently, an organic cation:H+ antiport was selectively identified on the sinusoidal domain of rat liver with the use of the endogenous organic cation N1-methylnicotinamide (NMN). Absence of NMN+:H+ exchange on canalicular membrane suggested that this transport process was primarily involved in organic cation uptake, leaving the mechanism(s) for organic cation secretion into bile unknown. To further define hepatic organic cation transport, we examined the characteristics of tetraethylammonium (TEA) transport in basolateral (blLPM) and canalicular (cLPM) rat liver plasma membrane vesicles. In cLPM vesicles, under voltage-clamped conditions, an outwardly directed H+ gradient stimulated [14C]TEA uptake compared with [14C]TEA uptake under pH-equilibrated conditions, consistent with electroneutral TEA:H+ exchange. The proton ionophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone had no effect on [14C]TEA uptake, demonstrating that pH-dependent [14C]TEA uptake was not the result of a H+ diffusion potential. In the absence of a pH gradient, the intravesicular presence of TEA trans-stimulated uptake of [14C]TEA. Procainamide ethobromide (PAEB), vecuronium, and tributylmethylammonium (TBuMA), organic cations selectively excreted in bile, cis-inhibited pH-dependent TEA uptake. In contrast, in blLPM vesicles, no pH gradient-dependent [14C]TEA uptake was demonstrated. Instead, basolateral [14C]TEA uptake was significantly stimulated by a valinomycin-induced intravesicular-negative K+ diffusion potential. Basolateral [14C]TEA uptake was also cis-inhibited by PAEB, vecuronium, and TBuMA, but not by NMN. Conversely, PAEB, vecuronium, and TBuMA had no effect on basolateral pH-dependent [3H]NMN uptake. These findings suggest that organic cation transport, with TEA as a model quaternary amine, across the canalicular membrane is driven by an electroneutral organic cation:H+ exchange and that the transport of certain organic cations across the basolateral membrane is via a carrier-mediated system stimulated by an inside-negative membrane potential.

Functional Impairment of Renal Organic Cation Transport in Experimental Diabetes

2002 ◽  
Vol 90 (4) ◽  
pp. 181-186 ◽  
Author(s):  
Brett Grover ◽  
Christopher Auberger ◽  
Rangaprasad Sarangarajan ◽  
William Cacini
Keyword(s):  
Functional Impairment ◽  
Organic Cation ◽  
Experimental Diabetes ◽  
Cation Transport ◽  
Organic Cation Transport

Peritubular organic cation transport in isolated rabbit proximal tubules

1994 ◽  
Vol 266 (3) ◽  
pp. F450-F458 ◽  
Author(s):  
C. E. Groves ◽  
K. K. Evans ◽  
W. H. Dantzler ◽  
S. H. Wright
Keyword(s):  
Organic Cation ◽  
High Capacity ◽  
Organic Cation Transporter ◽  
Cation Transport ◽  
Proximal Tubules ◽  
Organic Cation Transport ◽  
Inhibitory Potency ◽  
Renal Proximal Tubules ◽  
Michaelis Constants ◽  
Maximal Capacity

The physiological characteristics of peritubular organic cation transport were examined by measuring the transport of the organic cation tetraethylammonium (TEA) in rabbit renal proximal tubule suspensions and isolated nonperfused rabbit renal proximal tubules. Peritubular organic cation transport in both single S2 segments and suspensions of isolated renal proximal tubules was found to be a high-capacity, high-affinity, carrier-mediated process. For tubule suspensions, the maximal capacity of the carrier for TEA (Jmax) and the concentration of TEA at 1/2 Jmax (Kt) (1.49 +/- 0.21 nmol.min-1.mg dry wt-1 and 131 +/- 16 microM, respectively), did not differ significantly from those measured in single S2 segments (Jmax, 1.16 +/- 0.075 nmol.min-1.mg dry wt-1; Kt, 108 +/- 10 microM). In addition, the pattern of inhibition of peritubular TEA transport by long-chain n-tetraalkylammonium compounds (n = 1-5) was both qualitatively and quantitatively similar in single S2 segments and tubule suspensions, exhibiting an increase in inhibitory potency with increasing alkyl chain length. For example, in tubule suspensions, apparent Michaelis constants for inhibition of TEA uptake ranged from 1.3 mM for tetramethylammonium (TMA) to 0.8 microM for tetrapentylammonium (TPeA). To determine whether these compounds were substrates for the peritubular organic cation transporter, their effect on the efflux of [14C]TEA from tubule suspensions was examined. A concentration of 0.5 mM of the short-chain tetraalkyls TMA or TEA increased the efflux of [14C]TEA (i.e., trans-stimulated) from tubules in suspension. The longer-chain tetraalkyls tetrapropylammonium, tetrabutylammonium, and TPeA all decreased the efflux of [14C]TEA from tubules in suspension; TPeA completely blocked efflux.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of organic cation transport

2004 ◽  
Vol 449 (5) ◽  
pp. 423-441 ◽  
Author(s):  
Giuliano Ciarimboli ◽  
Eberhard Schlatter
Keyword(s):  
Organic Cation ◽  
Cation Transport ◽  
Organic Cation Transport

scholarly journals Organic cation transport in the rat kidney in vivo visualized by time-resolved two-photon microscopy

2007 ◽  
Vol 72 (4) ◽  
pp. 422-429 ◽  
Author(s):  
M. Hörbelt ◽  
C. Wotzlaw ◽  
T.A. Sutton ◽  
B.A. Molitoris ◽  
T. Philipp ◽  
...  
Keyword(s):  
Organic Cation ◽  
Rat Kidney ◽  
Cation Transport ◽  
Organic Cation Transport ◽  
Time Resolved ◽  
Two Photon Microscopy ◽  
Two Photon
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