RT Journal Article
SR Electronic
T1 Application of the Fluorescent Probe 1-Anilinonaphthalene-8-Sulfonate to the Measurement of the Nonspecific Binding of Drugs to Human Liver Microsomes
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 1711
OP 1717
DO 10.1124/dmd.111.039354
VO 39
IS 9
A1 McLure, James A.
A1 Birkett, Donald J.
A1 Elliot, David J.
A1 Williams, J. Andrew
A1 Rowland, Andrew
A1 Miners, John O.
YR 2011
UL http://dmd.aspetjournals.org/content/39/9/1711.abstract
AB The fluorescence of 1-anilinonaphthalene-8-sulfonate (ANS) in the presence of human liver microsomes (HLMs) is altered by drugs that bind nonspecifically to the lipid bilayer. The present study characterized the relationship between the nonspecific binding (NSB) of drugs to HLMs as measured by equilibrium dialysis and the magnitude of the change in baseline ANS fluorescence. Fraction unbound in incubations of HLMs (fu(mic)) was determined for 16 drugs (12 bases, 3 acids, and 1 neutral) with log P values in the range 0.1 to 6.7 at three concentrations (100, 200, and 500 μM). Changes in ANS fluorescence induced by each of the drugs in the presence of HLMs were measured by spectrofluorometry. Values of fu(mic) determined by equilibrium dialysis ranged from 0.08 to 1.0. Although NSB of the basic drugs tended to increase with increasing log P, exceptions occurred. Basic drugs generally caused an increase in ANS fluorescence, whereas the acidic and neutral drugs resulted in a decrease in ANS fluorescence. There were highly significant (p < 0.001) linear relationships between the modulus (absolute value) of the increment/decrement in ANS fluorescence and both fu(mic) (r = 0.90 to 0.96) and log(1 − fu(mic)/fu(mic)) (r = 0.85 to 0.92) at the three drug concentrations. Agreement between measured fu(mic) and that predicted by ANS fluorescence was very good (<10% variance) for a validation set of six compounds. The ANS fluorescence method provides an accurate measure of the NSB of drugs to HLMs. Physicochemical determinants other than log P and charge type influence the NSB of drugs to HLMs.