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Competitive inhibition of [ 14 C]‐TEA uptake in A549 cell monolayers by formoterol and salbutamol
Author(s) -
Salomon Johanna Jessica,
Hosoya Kenichi,
Ehrhardt Carsten
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1015.2
Subject(s) - chemistry , a549 cell , pharmacology , tetraethylammonium , agonist , formoterol , receptor , biochemistry , endocrinology , cell , potassium , biology , organic chemistry , budesonide , corticosteroid
Formoterol (For) and salbutamol (Sal), two β 2 ‐receptor agonistic drugs, are positively charged at physiological pH. Here, we investigated, if organic cation/carnitine transporters (OCT/Ns) are involved in the translocation of the drugs in human alveolar epithelial cells (A549). A549 cells were grown to confluent monolayers for 5 days. Investigation of OCT/N‐mediated transport was performed using [ 14 C]‐tetraethylammonium (TEA, 10 μM), [ 3 H]‐acetylcarnitine (5.5 nM, Ac‐Car) and the β 2 ‐agonists (both at 500 μM) in KRB. A549 monolayers were incubated for 30 min (TEA) or 20 min (Ac‐Car) at 37°C. Competitive inhibition studies were also performed in which TEA uptake (0.25 – 2 mM) was studied in the presence and absence of For and Sal for 30 min. The β 2 ‐agonists showed pronounced inhibition of TEA uptake into A549 monolayers. TEA uptake was decreased to 15.4% (For) and 54.5% (Sal) of control, respectively. Neither β 2 ‐receptor agonist had a significant effect on Ac‐Car uptake. Eadie‐Hofstee analysis of TEA uptake revealed linearity and Km values of 858.2 μM and 1050.6 μM in the presence of For and Sal, respectively, which was a 6.5‐fold (For) and 4.5‐fold (Sal) increase compared to control values. No significant change in V max was observed. Ki values were 115 μM (For) and 271 μM (Sal). β 2 ‐agonists competitively inhibited TEA uptake via OCTs, but no interaction between the drugs and OCTNs was found.