Aldosterone glucuronidation by human liver and kidney microsomes and recombinant UDP-glucuronosyltransferases: inhibition by NSAIDs.
OBJECTIVE
To characterize: i) the kinetics of aldosterone (ALDO) 18beta-glucuronidation using human liver and human kidney microsomes and identify the human UGT enzyme(s) responsible for ALDO 18beta-glucuronidation and ii) the inhibition of ALDO 18beta-glucuronidation by non-selective NSAIDs.


METHODS
Using HPLC and LC-MS methods, ALDO 18beta-glucuronidation was characterized using human liver (n= 6), human kidney microsomes (n= 5) and recombinant human UGT 1A1, 1A3, 1A4, 1A5, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, 2B10, 2B15, 2B17 and 2B28 as the enzyme sources. Inhibition of ALDO 18beta-glucuronidation was investigated using alclofenac, cicloprofen, diclofenac, diflunisal, fenoprofen, R- and S-ibuprofen, indomethacin, ketoprofen, ketorolac, meclofenamic acid, mefenamic acid, S-naproxen, pirprofen and tiaprofenic acid. A rank order of inhibition (IC(50)) was established and the mechanism of inhibition investigated using diclofenac, S-ibuprofen, indomethacin, mefenamic acid and S-naproxen.


RESULTS
ALDO 18beta-glucuronidation by hepatic and renal microsomes exhibited Michaelis-Menten kinetics. Mean (+/-SD) K(m), V(max) and CL(int) values for HLM and HKCM were 509 +/- 137 and 367 +/- 170 microm, 1075 +/- 429 and 1110 +/- 522 pmol min(-1) mg(-1), and 2.36 +/- 1.12 and 3.91 +/- 2.35 microl min(-1) mg(-1), respectively. Of the UGT proteins, only UGT1A10 and UGT2B7 converted ALDO to its 18beta-glucuronide. All NSAIDs investigated inhibited ALDO 18beta-G formation by HLM, HKCM and UGT2B7. The rank order of inhibition (IC(50)) of renal and hepatic ALDO 18beta-glucuronidation followed the general trend: fenamates > diclofenac > arylpropionates.


CONCLUSIONS
A NSAID-ALDO interaction in vivo may result in elevated intra-renal concentrations of ALDO that may contribute to the adverse renal effects of NSAIDs and their effects on antihypertensive drug response.
Knights
Kathleen M
KM
Department of Clinical Pharmacology, Flinders University, School of Medicine, Bedford Park, Adelaide 5042, Australia. Kathie.knights@flinders.edu.au
Winner
Leanne K
LK
Elliot
David J
DJ
Bowalgaha
Kushari
K
Miners
John O
JO
D000328:Adult; D000368:Aged; D000450:Aldosterone / Q000378:metabolism*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000378:metabolism / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D005260:Female; D020719:Glucuronides / Q000378:metabolism*; D014453:Glucuronosyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D020128:Inhibitory Concentration 50; D007668:Kidney / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008297:Male; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism*; D008875:Middle Aged
D000894:Anti-Inflammatory Agents, Non-Steroidal; D020719:Glucuronides; D000450:Aldosterone; D014453:Glucuronosyltransferase