Transport of temocaprilat into rat hepatocytes: role of organic anion transporting polypeptide.
The mechanism for hepatic uptake of temocaprilat, an angiotensin-converting enzyme inhibitor that is predominantly excreted into bile was studied using isolated rat hepatocytes and COS-7 cells expressing the organic anion transporting polypeptide (oatp1). The uptake of temocaprilat into isolated rat hepatocytes exhibited saturation with a Km of 20.9 microM and a Vmax of 0.21 nmol/min/mg protein. This uptake was temperature sensitive and was significantly reduced by metabolic inhibitors, a sulfhydryl-modifying reagent and an anion-exchange inhibitor, although the replacement of Na+ with Li+ in the medium did not affect the uptake. [3H]Temocaprilat uptake was inhibited by estradiol-17beta-D-glucuronide and dibromosulphophthalein, typical substrates for the Na+-independent organic anion transporter, in a concentration-dependent manner, whereas excess estradiol-17beta-D-glucuronide did not completely inhibit the uptake. Temocaprilat uptake into COS-7 cells transfected with oatp1 cDNA revealed a concentration-dependency with a Km of 46.7 microM, a value comparable with that obtained in isolated hepatocytes. The contribution of oatp1 to carrier-mediated hepatic uptake of temocaprilat was less than 50% by correcting the uptake clearance with that of estradiol-17beta-D-glucuronide. A good linear correlation was observed for the inhibitory effect of angiotensin-converting enzyme inhibitors (benazeprilat, cilazaprilat, delaprilat and enalaprilat) between isolated hepatocytes and oatp1-expressing cells. These data suggest that oatp1, along with another transporter(s), mediates the uptake of angiotensin-converting enzyme inhibitors into rat hepatocytes.
Ishizuka
H
H
Analytical and Metabolic Research Laboratories, Sankyo Co., Ltd., Shinagawa-ku, Tokyo 140, Japan.
Konno
K
K
Naganuma
H
H
Nishimura
K
K
Kouzuki
H
H
Suzuki
H
H
Stieger
B
B
Meier
P J
PJ
Sugiyama
Y
Y
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000493:pharmacokinetics* / Q000494:pharmacology; D000818:Animals; D027321:Anion Transport Proteins; D001692:Biological Transport / Q000187:drug effects; D019556:COS Cells; D002352:Carrier Proteins / Q000502:physiology; D008099:Liver / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000502:physiology; D013448:Sulfobromophthalein / Q000494:pharmacology; D013841:Thiazepines / Q000493:pharmacokinetics*
D000806:Angiotensin-Converting Enzyme Inhibitors; D027321:Anion Transport Proteins; D002352:Carrier Proteins; D013841:Thiazepines; D013448:Sulfobromophthalein; C012479:dibromosulphthalein; C069156:temocaprilat; D012964:Sodium