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[³H]-testosterone and [³H]-dihydrotestosterone were incubated with epithelium of the bovine cornea in vitro at 0–2^oC. Active transport from the medium into the tissue was demonstrated in both instances.The specific uptake of [³H]-testosteronewas 34.9 pmol/mg protein and of [³H]-dihydrotestosterone 45.0 pmol/mg protein. The specific uptake related to the amount of the incubated steroid was approximately equal for both androgens investigated (0.79 or 0.85%).

The effect of 15 mM methylxanthines (theophylline, coffeine) and 15 mM papaverine on T3 binding in the cytosol or nuclear extract receptors of human leukocytes was investigated by charcoal-dextran assay. In the cytosol, the presence of all three compounds increases the apparent association constants (KA) without affecting the total number of binding sites (N). Binding capacity was practically the same, only coffeine slightly decreases the number of binding sites. In the nuclear extract receptor protein, only theophylline increases its apparent affinity for T3.

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