Androgen-dependent regulation of androgen nuclear receptor in the rat ventral prostate.

Methods have been developed for the measurement of nonradioactive or radioactive dihydrotestosterone (DHT) bound to androgen receptor in rat ventral prostate nuclei (DHTRn). Using 1-day-castrated adult Sprague-Dawley rats (300--320 g body weight), the effects of testosterone (T) on nuclear androgen receptor formation were investigated in the absence and presence of cycloheximide or emetine. DHTRn was measured 4 h after injection of increasing amounts of T, and a maximal value of 14.

Competitive inhibition of specific steroid-protein binding: practical use of relative competition ratios for the derivation of equilibrium inhibition constants.

The relative competition ratio (RCR) is widely used to express the relative affinities of inhibitor(s) and agonist for a binding protein. The RCR is not a constant; it depends on the concentrations of binding sites and of radioactive hormone, and on the presence of nonsaturable binding component(s). According to the assay conditions used, equating the RCR value to the ratio Ka/Ki of the equilibrium association constants of agonist and inhibitor can lead to large errors.

[Androgen binding proteins in the rat prostate: methodological problems and regulation (author's transl)].

Protamine sulfate precipitation is used for the selective and quantitative assay of equilibrium binding constants. The association constant of dihydrotestosterone is 1 X 10(9)1/mole and the number of binding sites is 11.500/cell.

Determination of protein-ligand binding constants at equilibrium in biological samples.

Protein-ligand complexes can be separated functionally into two classes. "Specific" binding is characterized, in relative terms, by a high affinity for the ligand and a low binding capacity. "Non-specific" binding is characterized by a low affinity and a very large capacity.