7-Alkoxyquinolines: new fluorescent substrates for cytochrome P450 monooxygenases.
A series of 7-alkoxyquinolines was synthesized and tested as substrates with hepatic microsomes prepared from male Wistar rats. Microsomal O-dealkylation rates and kinetic constants were determined for the 7-alkoxyquinolines with microsomes from control, 3-methylcholanthrene (MC)-pretreated, and phenobarbitone (PB)-pretreated rats. Structure-activity relationship studies indicated that the 7-benzyloxyquinoline was the most rapidly metabolized substrate for control microsomes and those from PB-pretreated rats, whereas the 7-ethoxy- and 7-propoxyquinolines were O-dealkylated more rapidly by microsomes of MC-pretreated animals. Differences in activities occurred in Vmax and apparent Km values; however, there does not appear to be a correlation between these two values for the different quinoline substrates. Apparent Km and Vmax values for the 7-alkoxyquinolines were: control microsomes, Km = 71-773 microM, Vmax = 0.37-8.4 nmol 7-quinolinol/min/mg protein; MC microsomes, Km = 0.5-14 microM, Vmax = 0.29-2.7 nmol 7-quinolinol/min/mg protein; PB microsomes, Km = 2.8-46 microM, Vmax = 0.9-12 nmol 7-quinolinol/min/mg protein. All of the quinoline substrates gave Type I binding spectra with control and MC microsomes. With PB microsomes, Type I. Reverse Type I, and a mixture of the two types of binding spectra were observed. Comparisons of the structure-activity relationships, levels of induction, and kinetic constants were made with 7-alkoxycoumarin and 7-alkoxyphenoxazone analogs. In addition, three new coumarin substrates (7-pentoxy-, 7-hexoxy-, and 7-benzyloxycoumarin) are described.
Mayer
R T
RT
U.S. Department of Agriculture, Agricultural Research Service, U.S. Horticultural Research Laboratory, Orlando, FL 32803.
Netter
K J
KJ
Heubel
F
F
Hahnemann
B
B
Buchheister
A
A
Mayer
G K
GK
Burke
M D
MD
D000818:Animals; D003374:Coumarins / Q000138:chemical synthesis / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D010078:Oxazines / Q000138:chemical synthesis / Q000378:metabolism; D011804:Quinolines / Q000138:chemical synthesis* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D003374:Coumarins; D010078:Oxazines; D011804:Quinolines; C065955:7-hexoxyquinoline; C065956:7-benzyloxyquinoline; C059160:7-methoxyquinoline; D003577:Cytochrome P-450 Enzyme System