Mechanism of Inhibition of Adrenal Steroid 11β-Hydroxylase by Methopyrapone (Metopirone)

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Abstract
To determine the type of inhibition of 11β-hydroxylation produced by Metopirone, deoxycorticosterone-4-C14 was incubated with rat adrenal homogenates in a medium of 50% bovine blood serum, 50% Krebs bicarbonate buffer, pH 7.4, containing an excess of TPNH, and the production of corticosterone and 11-dehydrocorticosterone was measured. Different concentrations of substrate and Metopirone were used. The data were plotted according to Lineweaver and Burk and according to Dixon. The results indicated pure competitive inhibition within the limits of error of the method. Metopirone did not inhibit 21-hydroxylation significantly under the same conditions.