Direct quantitative digital autoradiography of testosterone metabolites in the pilosebaceous unit: an environmentally...

Androgen metabolism is one of the major keys for a better understanding of conditions such as androchronogenetic alopecia, acne, and other androgen-related skin disorders. This paper addresses the process by which testosterone metabolism leads to the following major androgens: androstenedione, dihydrotestosterone, 3 alpha- and 3 beta-androstanediol, androsterone, epiandrosterone, and androstanedione. Our report describes a methodology developed for the direct quantitative measurement from the silica gel plate of these metabolites. After detailing the chromatographic procedures to achieve the complete separation of the seven testosterone metabolites on a single plate, specifications are given for obtaining accurate measurements by 1) calibration of the radiodetectors and 2) internal and external standardization of samples and plates. Analytical criteria are discussed in terms of comparison of the level of sensitivity, reproducibility, and practicability obtained by both the linear analyzer and the direct digital autoradiograph. Signals as weak as 25 dpm were easily detected and calibration curves were obtained for the range of 50-500 dpm. For biological measurements the coefficients of variation do not exceed 10%. Given the difficulty of obtaining large amounts of microdissected subfractions of the pilosebaceous unit and the necessity of evaluating the complete pattern of testosterone transformed into its 3 alpha,3 beta-, 5 alpha-reduced and 17 beta-dehydrogenated secondary derivatives, digital autoradiography appears to be a powerful yet simple tool for studying androgen metabolism. In addition, this methodology offers an important environmental advantage: the high sensitivity of the detectors makes it possible to minimize the quantities of radioactive materials that must be handled or discarded.