Pharmacokinetic Analysis of Transcellular Transport of Quinidine across Monolayers of Human Intestinal Epithelial Caco-2 Cells

Abstract

Quinidine, a tertiary amine compound with a site of ionization with a pK a value of pH 8.8, is classified as a type IA antiarrhythmic drug, and has been used for the management of ventricular arrhythmias.1,2) The drug is absorbed rapidly and almost entirely after oral administration, and is detected in the plasma within 15 min.3) Quinidine binds to both albumin and a 1 -acid glycoprotein, and the proportion that binds to plasma protein is 70 to 95%. 4) However, its apparent volume of distribution is quite large (2.0 to 3.5 liters/kg), because the drug is highly lipophilic.4) It is metabolized via 3-hydroxylation and N-oxygenation by cytochrome P450 3A4, and these metabolites are less electrophysiologically active than the parent drug. 5,6) The hepatic extraction ratio of quinidine is about 30%, and the bioavailability after oral administration is about 70%. 7) In addition, quinidine is partly excreted in the urine (15 to 40% of dose), suggesting that reabsorption at the distal tubules in the nephron is not complete. 4)The mechanism of intestinal absorption of lipophilic organic cations has been explained as passive diffusion of unionized compounds according to the pH-partition theory. On the other hand, Mizuuchi et al. investigated the mechanisms responsible for the transcellular transport of diphenhydramine in Caco-2 cells. 8,9) This cell line forms confluent monolayers of well differentiated enterocyte-like cells with functional properties of transporting epithelia, and is widely used as a model to study the absorption of drugs and other xenobiotics.10-12) The uptake of diphenhydramine at the apical membrane in Caco-2 cells was pH-and temperature-dependent, but was not inhibited by tetraethylammonium, biological amines, or neurotransmitters.8) On the other hand, the uptake was inhibited by chlorpheniramine, procainamide, and imipramine, and was trans-stimulated by the preloading of chlorpheniramine, dimethylaminochloride, and triethylamine.8,9) From these results, Mizuuchi et al. concluded that the uptake of diphenhydramine at the apical membrane in Caco-2 cells is mediated by a specific transport system, and that this system recognizes the N-dimethyl or N-diethyl moieties of compounds. 8,9) However, at present, it is unclear whether the transport system for diphenhydramine is involved in the intestinal absorption of other tertiary amine compounds, such as quinidine.During drug absorption in the intestine, therapeutic compounds or nutrients first enter intestinal epithelial cells from their apical side, then pass through the epithelia to the basolateral side, and finally appear in the blood stream. Therefore, to investigate intestinal drug absorption, it is important to separately assess these sequential processes. However, in many cases, drug transport on the apical and basolateral sides of the monolayer in Caco-2 cells was not separately examined, and the influx and efflux clearance rates were not evaluated.13) For the characterization of transcellular drug transport, a pharmacokinetic approach is useful. Tr...

Membrane Transport Mechanisms of Quinidine and Procainamide in Renal LLC-PK1 and Intestinal LS180 Cells

“…2,7) In the present study, to confirm the involvement of the cation transport system in intestinal absorption of quinidine, we investigated the membrane transport mechanism of quinidine using another intestinal epithelial cell line, LS180. This cell line possesses characteristics of the small intestine (e.g., expression of microvillus), and has also been used as an in vitro model of the intestine.…”

“…2,7) The cellular uptake of quinidine in Caco-2 cells grown on plastic dishes was temperature-dependent, and markedly increased by alkalization of the apical medium at 37°C.…”

“…TEER was measured using a Millicell-ERS resistance system (Millipore, Bedford, MA, U.S.A.). LLC-PK 1 cell monolayers whose TEER was above 60 W · cm 2 were used to assess the transcellular transport of cationic drugs. ]procainamide in LLC-PK 1 cell monolayers prepared on a porous membrane was examined as described previously.…”

“…2,7) In the present study, we investigated whether the cation transport system for quinidine is present in another human intestinal epithelial cell line, LS180. Figure 2A shows the time course of the uptake of 100 mM quinidine at 37°C and 4°C in LS180 cells grown on plastic dishes.…”

Stereoselective Metabolism of Carvedilol by the .BETA.-Naphthoflavone-Inducible Enzyme in Human Intestinal Epithelial Caco-2 Cells

“…12,13) In addition, several UGTs, such as UGT1A1, 1A6, and 2B7, are expressed in Caco-2 cells, and the expression of some UGTs is induced by aromatic hydrocarbon receptor (AhR) ligands, such as b-naphthoflavone (b-NF).…”