Evidence for the existence of a specific binding site for indomethacin on bovine vesicular gland microsomes.
Using bovine vesicular gland microsomes and [14C]indomethacin we demonstrated the presence of a specific binding site for nonsteroidal anti-inflammatory drugs. Specific binding of [14C]indomethacin to microsomes was rapid, with most of the ligand bound by 2 min at 4 degrees C. In routine binding assays the incubation temperature was maintained at 4 degrees C, because the maximal specific binding was obtained. Specific [14C]indomethacin binding appeared to increase linearly with increasing protein concentration over the range of 0.1-1.0 mg of microsomal protein. Specific binding was saturable and Scatchard analysis of binding data showed a single class of binding sites with a dissociation constant (Kd) of 3.8 microM and a maximal number of binding sites (Bmax) of about 1272 pmol/mg of protein. When these binding data were plotted according to the Hill equation, a straight line was obtained with a Hill coefficient of 1.0. Structural specificity of the nonsteroidal anti-inflammatory drug site was studied with diclofenac, arylpropionic acids (ketoprofen and indoprofen), and aspirin. Diclofenac and arylpropionic derivatives were able to compete with [14C]indomethacin for binding to microsomes, while aspirin was a weak inhibitor.
Mazzoni
M R
MR
Istituto Policattedra di Discipline Biologiche, University of Pisa, Italy.
Lucacchini
A
A
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D001667:Binding, Competitive; D002417:Cattle; D007213:Indomethacin / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000378:metabolism*; D012669:Seminal Vesicles / Q000378:metabolism*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D007213:Indomethacin