TY - JOUR
T1 - Organic cation uptake by a cultured renal epithelium
AU - McKinney, T. Dwight
AU - DeLeon, Catherine
AU - Speeg, K. Vincent
PY - 1988/12
Y1 - 1988/12
N2 - Several organic cations are actively transported by proximal renal tubules by mediated processes across both the apical and basolateral cell membranes. In order to evaluate this transport system in a cultured renal epithelium, uptake of 3H‐tetraethylammonium (TEA) across the apical membrane was measured in LLCPK1 cells, a cell line with several characteristics of proximal tubules. 3H‐TEA progressively entered these cells and reached a near‐steady state by 30 min. Three‐minute uptake was saturable with an apparent Vmax of 1,669 ± 129 fmoles/μg DNA and apparent Km of 34.0 ± 3.4 μM. 3H‐TEA uptake was inhibited by an excess of nonradioactive TEA, other organic cations, sodium azide, and hypothermia. An alkaline external pH was associated with greater 3H‐TEA uptake than an acid pH. However, efflux of 3H‐TEA from cells was not appreciably affected by changes in external pH. Preincubation of cells in acid or alkaline media did not affect uptake. Alteration of cell pH by ammonium chloride addition or removal had little effect on 3H‐TEA uptake. Finally, uptake of 3H‐TEA was not accelerated by preloading cells with an excess of nonradioactive TEA. These results indicate that intact LLCPK1 cells possess a mechanism(s) in their apical membranes for the mediated transport of a prototypic organic cation. The mechanism(s) involved in this transport is uncertain. However, neither organic cation/proton nor organic cation/organic cation exchange appears to be the predominant process.
AB - Several organic cations are actively transported by proximal renal tubules by mediated processes across both the apical and basolateral cell membranes. In order to evaluate this transport system in a cultured renal epithelium, uptake of 3H‐tetraethylammonium (TEA) across the apical membrane was measured in LLCPK1 cells, a cell line with several characteristics of proximal tubules. 3H‐TEA progressively entered these cells and reached a near‐steady state by 30 min. Three‐minute uptake was saturable with an apparent Vmax of 1,669 ± 129 fmoles/μg DNA and apparent Km of 34.0 ± 3.4 μM. 3H‐TEA uptake was inhibited by an excess of nonradioactive TEA, other organic cations, sodium azide, and hypothermia. An alkaline external pH was associated with greater 3H‐TEA uptake than an acid pH. However, efflux of 3H‐TEA from cells was not appreciably affected by changes in external pH. Preincubation of cells in acid or alkaline media did not affect uptake. Alteration of cell pH by ammonium chloride addition or removal had little effect on 3H‐TEA uptake. Finally, uptake of 3H‐TEA was not accelerated by preloading cells with an excess of nonradioactive TEA. These results indicate that intact LLCPK1 cells possess a mechanism(s) in their apical membranes for the mediated transport of a prototypic organic cation. The mechanism(s) involved in this transport is uncertain. However, neither organic cation/proton nor organic cation/organic cation exchange appears to be the predominant process.
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U2 - 10.1002/jcp.1041370317
DO - 10.1002/jcp.1041370317
M3 - Article
C2 - 3192630
AN - SCOPUS:0024268393
VL - 137
SP - 513
EP - 520
JO - Journal of Cellular Physiology
JF - Journal of Cellular Physiology
SN - 0021-9541
IS - 3
ER -