| 7948786 |
Bendayan R, Lo B, Silverman M: Characterization of cimetidine transport in LLCPK1 cells. J Am Soc Nephrol. 1994 Jul;5(1):75-84.
In this study, cimetidine uptake and its regulation by LLCPK1 monolayers were investigated. Uptake was temperature dependent with kinetic and specificity characteristics typical of a carrier-mediated mechanism. With cimetidine uptake in the presence of an excess concentration of the potent inhibitor quinidine as a measure of nonspecific transport, the estimated kinetic parameters for cimetidine uptake at 37 degrees C under steady-state conditions are Km = 32.3 +/- 6.4 microM and Vmax = 20.2 +/- 2.1 pmol/mg per minute. Amiloride, quinidine, and quinine inhibited cimetidine uptake, whereas N1-methylnicotinamide, tetraethylammonium, and guanidine did not. The uptake of cimetidine was increased in the presence of a cell--> lumen H+ gradient, consistent with the behavior of a cimetidine-H+ antiport system. Furthermore, the activity of both the Na (+)-H+ exchanger and H (+)-ATPase acted to dissipate the cell--> lumen H+ gradient, thereby decreasing net cimetidine transport. These results suggest that there is a cimetidine-H+ exchange system in LLCPK1 cells and that the net secretion of organic base in vivo may be regulated by luminal acidification mechanisms. |
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