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Modulation of uptake of organic cationic drugs in cultured human colon adenocarcinoma Caco‐2 cells by an ecto‐alkaline phosphatase activity
Author(s) -
Calhau C.,
Martel F.,
HipólitoReis C.,
Azevedo I.
Publication year - 2002
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/jcb.10306
Subject(s) - caco 2 , alkaline phosphatase , colon adenocarcinoma , chemistry , cationic polymerization , phosphatase , adenocarcinoma , modulation (music) , biochemistry , pharmacology , in vitro , cancer research , medicine , biology , enzyme , cancer , organic chemistry , philosophy , aesthetics
Alkaline phosphatase (ALP) refers to a group of nonspecific phosphomonoesterases located primarily in cell plasma membrane. It has been described in different cell lines that ecto‐ALP is directly or indirectly involved in the modulation of organic cation transport. We aimed to investigate, in Caco‐2 cells, a putative modulation of 1‐methyl‐4‐phenylpyridinium (MPP + ) apical uptake by an ecto‐ALP activity. Ecto‐ALP activity and 3 H‐MPP + uptake were evaluated in intact Caco‐2 cells (human colon adenocarcinoma cell line), in the absence and presence of a series of drugs. The activity of membrane‐bound ecto‐ALP expressed on the apical surface of Caco‐2 cells was studied at physiological pH using p ‐nitrophenylphosphate as substrate. The results showed that Caco‐2 cells express ALP activity, characterized by an ecto‐oriented active site functional at physiological pH. Genistein (250 µM), 3‐isobutyl‐1‐methylxanthine (1 mM), verapamil (100 µM), and ascorbic acid (1 mM) significantly increased ecto‐ALP activity and decreased 3 H‐MPP + apical transport in this cell line. Orthovanadate (100 µM) showed no effect on 3 H‐MPP + transport and on ecto‐ALP activity. On the other hand, okadaic acid (310 nM) and all trans ‐retinoic acid (1 µM) significantly increased 3 H‐MPP + uptake and inhibited ecto‐ALP activity. There is a negative correlation between the effect of drugs upon ecto‐ALP activity and 3 H‐MPP + apical transport ( r = −0.9; P = 0.0014). We suggest that apical uptake of organic cations in Caco‐2 cells is affected by phosphorylation/dephosphorylation mechanisms, and that ecto‐ALP activity may be involved in this process. J. Cell. Biochem. 87: 408–416, 2002. © 2002 Wiley‐Liss, Inc.