NBD-TMA: a novel fluorescent substrate of the peritubular organic cation transporter of renal proximal tubules

2000 ◽  
Vol 440 (1) ◽  
pp. 184 ◽  
Author(s):  
Dallas Bednarczyk ◽  
Eugene A. Mash ◽  
Bhasker Reddy Aavula ◽  
Stephen H. Wright
Keyword(s):  
Organic Cation ◽  
Organic Cation Transporter ◽  
Proximal Tubules ◽  
Fluorescent Substrate ◽  
Renal Proximal Tubules

Role of MAPK and PKA in regulation of rbOCT2-mediated renal organic cation transport

2007 ◽  
Vol 293 (1) ◽  
pp. F21-F27 ◽  
Author(s):  
Sunhapas Soodvilai ◽  
Atip Chatsudthipong ◽  
Varanuj Chatsudthipong
Keyword(s):  
Organic Cation ◽  
Chinese Hamster ◽  
Organic Cation Transporter ◽  
Inhibitory Effect ◽  
Cell System ◽  
Proximal Tubules ◽  
Common Pathway ◽  
Renal Proximal Tubules ◽  
Organic Cation Transporter 2 ◽  
Heterologous Cell

The effects of protein kinases MAPK and PKA on the regulation of organic cation transporter 2 (OCT2) were investigated both in a heterologous cell system [Chinese hamster ovary (CHO-K1) cells stably transfected with rabbit (rb)OCT2] and in native intact rabbit renal proximal S2 segments. Inhibition of MEK (by U-0126) or PKA (by H-89) reduced transport activity of rbOCT2 in CHO-K1 cells. The inhibitory effect of U-0126 combined with H-89 produced no additive effect, indicating that the action of PKA and MAPK in the regulation of rbOCT2 is in a common pathway. Activation of PKA by forskolin stimulated rbOCT2 activity, and this stimulatory effect was eliminated by H-89, indicating that the stimulation required PKA activation. In S2 segments of rabbit renal proximal tubules, activation of MAPK (by EGF) and PKA (by forskolin) stimulated activity of rbOCT2, and this activation was abolished by U-0126 and H-89, respectively. This is the first study to show that MAPK and PKA are involved, apparently in a common pathway, in the regulation of OCT2 activity in both a heterologous cell system and intact renal proximal tubules.

Daunomycin secretion by killfish renal proximal tubules

1995 ◽  
Vol 269 (2) ◽  
pp. R370-R379 ◽  
Author(s):  
D. S. Miller
Keyword(s):  
Organic Cation ◽  
Basolateral Membrane ◽  
Organic Cation Transporter ◽  
Proximal Tubules ◽  
Epifluorescence Microscopy ◽  
Buffer Solution ◽  
Simple Diffusion ◽  
Renal Proximal Tubules ◽  
Cellular Accumulation ◽  
Tubular Lumen

Epifluorescence microscopy and video-image analysis were used to measure the uptake of the fluorescent anthracycline daunomycin by intact killifish renal proximal tubules. When tubules were incubated in medium containing 2-5 microM daunomycin, the drug accumulated in the cells and the tubular lumen. At steady state, luminal fluorescence was two to three times greater than cellular fluorescence. Luminal accumulation of daunomycin was reduced when tubules were exposed to the multidrug-resistance (MDR) transporter modifiers verapamil and cyclosporin A (CSA), but not tetraethylammonium (TEA), a model substrate for the renal organic cation transport system. NaCN and vanadate reduced luminal drug accumulation. In contrast, cellular daunomycin accumulation was not affected by verapamil, CSA, TEA, or vanadate and was only slightly reduced by NaCN. When the pH of the buffer solution was decreased from 8.25 to 7.25, luminal, but not cellular, accumulation of daunomycin was again reduced by CSA; however, TEA now reduced cellular and luminal accumulation. These findings are consistent with daunomycin being actively secreted in killifish proximal tubule by two mechanisms. At pH 8.25, daunomycin crossed the basolateral membrane by simple diffusion and was secreted into the tubular lumen by the MDR transporter. At pH 7.25, daunomycin was transported across the basolateral membrane by simple diffusion and carrier-mediated uptake on the organic cation transporter and was secreted into the lumen by the MDR transporter and the organic cation/H+ exchanger.

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)

Tetraspanin CD63 controls basolateral sorting of organic cation transporter 2 in renal proximal tubules

2016 ◽  
Vol 31 (4) ◽  
pp. 1421-1433 ◽  
Author(s):  
Ulf Schulze ◽  
Sabine Brast ◽  
Alexander Grabner ◽  
Christian Albiker ◽  
Beatrice Snieder ◽  
...  
Keyword(s):  
Organic Cation ◽  
Organic Cation Transporter ◽  
Proximal Tubules ◽  
Renal Proximal Tubules ◽  
Organic Cation Transporter 2 ◽  
Tetraspanin Cd63

Functional characterization of ORCTL2 - an organic cation transporter expressed in the renal proximal tubules

FEBS Letters ◽  
1998 ◽  
Vol 433 (3) ◽  
pp. 245-250 ◽  
Author(s):  
Mark Reece ◽  
Dirk Prawitt ◽  
John Landers ◽  
Christina Kast ◽  
Philippe Gros ◽  
...  
Keyword(s):  
Organic Cation ◽  
Functional Characterization ◽  
Organic Cation Transporter ◽  
Proximal Tubules ◽  
Renal Proximal Tubules

Basolateral localization of organic cation transporter 2 in intact renal proximal tubules

2000 ◽  
Vol 279 (5) ◽  
pp. F826-F834 ◽  
Author(s):  
Douglas H. Sweet ◽  
David S. Miller ◽  
John B. Pritchard
Keyword(s):  
Plasma Membrane ◽  
Organic Cation ◽  
Apical Membrane ◽  
Organic Cation Transporter ◽  
Proximal Tubules ◽  
Renal Cells ◽  
Renal Proximal Tubules ◽  
Lateral Membrane ◽  
Organic Cation Transporter 2 ◽  
Specific Potential

The localization of organic cation transporter 2 (OCT2) within renal cells is the subject of considerable controversy, resulting in marked uncertainty as to its function. To resolve this issue, we made an OCT2/green fluorescent protein (GFP) fusion construct (rOCT2-GFP) and determined its localization within Xenopus laevis oocytes and renal cells using confocal microscopy. Oocytes expressing rOCT2-GFP exhibited plasma membrane fluorescence as well as greatly increased specific, potential-driven uptake of [14C]tetraethylammonium (TEA). Polarized monolayers of renal epithelial cell lines [LLC-PK1 and Madin-Darby canine kidney (MDCK)] transiently transfected with pEGFP-C3, which codes for a cytoplasmic GFP, showed a diffuse, evenly distributed cytoplasmic signal with no plasma membrane fluorescence. In contrast, cells transiently transfected with pEGFP-C3/rOCT2 (the vector coding for rOCT2-GFP) showed predominantly plasma membrane fluorescence, which was most prominent in the lateral membrane. MDCK cells stably expressing rOCT2-GFP (MDCK/rOCT2-GFP) maintained in long-term culture showed a greatly increased basal and lateral membrane fluorescence. When grown on porous supports, MDCK/rOCT2-GFP monolayers showed specific, potential-driven TEA uptake from the basal side. Finally, expression and distribution of rOCT2-GFP were investigated in isolated killifish ( Fundulus heteroclitus) renal proximal tubules. On expression of rOCT2-GFP, transfected tubules showed marked basal and lateral membrane fluorescence, with no detectable signal at the apical membrane. In contrast, tubules expressing a luminal sodium-dicarboxylate cotransporter (rbNaDC-1)-GFP construct showed apical membrane fluorescence, and tubules expressing cytoplasmic GFP had a diffuse cytoplasmic fluorescence. These results indicate that rOCT2 is basolateral in renal proximal tubule cells.

scholarly journals Organic cation transporter 3 contributes to norepinephrine uptake into perivascular adipose tissue

2015 ◽  
Vol 309 (11) ◽  
pp. H1904-H1914 ◽  
Author(s):  
Nadia Ayala-Lopez ◽  
William F. Jackson ◽  
Robert Burnett ◽  
James N. Wilson ◽  
Janice M. Thompson ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Organic Cation ◽  
Organic Cation Transporter ◽  
Confocal Imaging ◽  
Uptake System ◽  
Sprague Dawley ◽  
Uptake Mechanism ◽  
Fluorescent Substrate ◽  
Perivascular Adipose Tissue ◽  
Organic Cation Transporter 3

Perivascular adipose tissue (PVAT) reduces vasoconstriction to norepinephrine (NE). A mechanism by which PVAT could function to reduce vascular contraction is by decreasing the amount of NE to which the vessel is exposed. PVATs from male Sprague-Dawley rats were used to test the hypothesis that PVAT has a NE uptake mechanism. NE was detected by HPLC in mesenteric PVAT and isolated adipocytes. Uptake of NE (10 μM) in mesenteric PVAT was reduced by the NE transporter (NET) inhibitor nisoxetine (1 μM, 73.68 ± 7.62%, all values reported as percentages of vehicle), the 5-hydroxytryptamine transporter (SERT) inhibitor citalopram (100 nM) with the organic cation transporter 3 (OCT3) inhibitor corticosterone (100 μM, 56.18 ± 5.21%), and the NET inhibitor desipramine (10 μM) with corticosterone (100 μM, 61.18 ± 6.82%). Aortic PVAT NE uptake was reduced by corticosterone (100 μM, 53.01 ± 10.96%). Confocal imaging of mesenteric PVAT stained with 4-[4-(dimethylamino)-styrl]- N-methylpyridinium iodide (ASP+), a fluorescent substrate of cationic transporters, detected ASP+ uptake into adipocytes. ASP+ (2 μM) uptake was reduced by citalopram (100 nM, 66.68 ± 6.43%), corticosterone (100 μM, 43.49 ± 10.17%), nisoxetine (100 nM, 84.12 ± 4.24%), citalopram with corticosterone (100 nM and 100 μM, respectively, 35.75 ± 4.21%), and desipramine with corticosterone (10 and 100 μM, respectively, 50.47 ± 5.78%). NET protein was not detected in mesenteric PVAT adipocytes. Expression of Slc22a3 (OCT3 gene) mRNA and protein in PVAT adipocytes was detected by RT-PCR and immunocytochemistry, respectively. These end points support the presence of a transporter-mediated NE uptake system within PVAT with a potential mediator being OCT3.

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