Carrier-Mediated Active Transport of the Glucuronide and Sulfate of 6-Hydroxy-5,7-dimethyl-2-methylamino-4-(3-pyridylmethyl) benzothiazole (E3040) into Rat Liver: Quantitative Comparison of Permeability in Isolated Hepatocytes, Perfused Liver and Liver in Vivo
- 1Tsukuba Research Laboratories, Eisai Co., Ltd., Tokodai, Tsukuba-shi, Ibaraki 300-26, Japan (O.T., T.H.) and 2Faculty of Pharmaceutical Sciences, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113, Japan (H.S., Y.S.)
Abstract
The hepatic uptake of glucuronic acid and sulfate conjugates of 6-hydroxy-5,7-dimethyl-2-methylamino-4-(3-pyridylmethyl) benzothiazole (E3040), a dual inhibitor of 5-lipoxygenase and thromboxane A2 synthetase, was investigated in rats. The biliary excretion clearance values for the glucuronide and the sulfate, obtained after i.v. administration of E3040, were similar and corresponded to approximately 30% of the hepatic blood flow rate. The influx clearance values of E3040 conjugates in the presence of 3% bovine serum albumin, measured by a multiple indicator dilution method in the perfused liver, were 1.20 ml/min/g liver for the glucuronide and 0.74 ml/min/g liver for the sulfate, which were twice and equal to the normal hepatic plasma flow rate, respectively, which suggests the presence of an efficient transport system(s). The uptake of E3040 conjugates into the isolated hepatocytes is mediated by Na+-independent active transport system(s), which is inhibited by dibromosulfophthalein and bile acids. The uptake for the sulfate had high-affinity and high-capacity transport activity (Km = 25 μM; V max = 7.8 nmol/min/106 cells) compared with that for the glucuronide (Km = 59 μM; V max = 2.2 nmol/min/106 cells). The uptakes of E3040 conjugates (glucuronide, sulfate) exhibited a mutual competitive inhibition. It is suggested that both conjugates share a multispecific organic anion transporter located on the sinusoidal membrane.
Footnotes
-
Send reprint requests to: Yuichi Sugiyama, Ph.D., Faculty of Pharmaceutical Sciences, The University of Tokyo, Hongo Bunkyo-ku, Tokyo 113, Japan.
- Abbreviations:
- E3040
- 6-hydroxy-5,7-dimethyl-2-methylamino-4-(3-pyridylmethyl) benzothiazole
- [14C]E3040
- [2-14C]6-hydroxy-5,7-dimethyl-2-methylamino-4-(3-pyridylmethyl) benzothiazole dihydrochloride
- SD rats
- Sprague-Dawley rats
- DBSP
- dibromosulfophthalein
- HEPES
- N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid
- MID method
- multiple indicator dilution method
- HPLC
- high-performance liquid chromatography
- BSA
- bovine serum albumin
- TLC
- thin-layer chromatography
- AUC∞
- the area under the plasma concentration-time profiles from zero to infinity
- CLbile
- the biliary excretion clearance
- CLrenal
- the urinary excretion clearance
- CLu,renal
- the unbound urinary excretion clearance
- Xbile
- the amount excreted into the bile
- Xurine
- the amount excreted into the urine
- CLtot
- the total body clearance
- PSinf
- the influx clearance
- PSu,inf
- the unbound influx clearance
- Kinf
- the influx rate constant
- Keff
- the efflux rate constant
- Kseq
- the sequestration rate constant
- Km
- Michaelis constant
- Vmax
- maximal uptake rate
- Pdif
- the nonspecific uptake clearance
- LUR
- the first-pass liver uptake ratio
- UWL
- the unstirred water layer
- PCMBS
- p-chloromercuriphenylsulfonic acid
- DIDS
- 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid
- FCCP
- carbonyl cyanide-p-(trifluoromethoxy)-phenylhydrazone
- C/M
- cell-to-medium concentration
-
- Received May 24, 1996.
- Accepted October 30, 1996.
- The American Society for Pharmacology and Experimental Therapeutics
