Aromatization of testosterone in large and small bovine luteal cells. Conflicting results between radioimmunoassay and cocrystallization data

The ability of isolated large or small bovine luteal cells to synthesize estradiol-17β was tested by incubations in the absence or in the presence of exogenous testosterone.Using a specific radioimmunoassay, no synthesis of estradiol-17β could be detected in the small or large luteal cells after incubation in the absence of testosterone. However, after incubation in the presence of exogenous unlabelled testosterone, radioimmunoassay data suggested the existence in the large but not the small luteal cells of synthesis of estradiol-17β. However, the results obtained by measuring the conversion of ³H-testosterone to ³H-estradiol-17β by cocrystallization with unlabelled estradiol-17β failed to confirm the presence of aromatase in the large cells. These data indicate that aromatization in large and small bovine luteal cells is probably negligible. Moreover, they cast serious doubt on studies of aromatization in luteal tissue based on radioimmunoassay data only.