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Mechanisms of Aging in Relationship to Steroid Biotransformations And Thiobarbituric Acid Reactive Material in Rat Testicular Tissue Ln Vitro by Mario H. Baptista, Doctor of Philosophy Utah State University, 1969 Major Professors Dr. LeGrande C. Ellis Department: Physiology The changes with age in the steroid bioconversions by testicular tissue _in vitro were investigated in rats varying in age from 4 days to 3 2 years. The incubations were carried out with both pregnenolone-lotH 14 and progesterone-4C as substrates with no cofactors added to the incubation medium. The different steroid fractions were separated and purified by paper chromatography with the Zaffaroni solvent systems and by derivative formation. Quantitation of the steroid metabolites was accomplished by liquid scintillation spectrometry with the results expressed as millimicromoles of the parent steroids appearing in the different steroid fractions. Two types of testicular preparations were utilized, teased-seminiferous tubules and testicular mince. Teasedseminiferous tubules from animals 30 and 90 days and 2 years of age were incubated for 2\ hours under atmospheric air at Zl^Q.. On both a per incubation and a per animal basis, the seminiferous tubules from 3-month-old animals demonstrated a greater ability for androgen production. Tubules from 1and 3-month-old animals incorporated more X carbon-14 than tritium into testosterone, but approximately four times more tritium than carbon-14 appeared in the testosterone recovered from incubations of tissue from 2-year-old animals. Substantial amounts of pregnanedione and of another compound, tentatively identified as 20ahydroxy-pregnan-3-one, were produced by the teased-tubular preparations. The high production of the above compounds suggests that they are the means by which the seminiferous tubules rid themselves of an excess of progesterone and other antiandrogenic steroids. These results correlated well with previous reports in the literature on the ability of the seminiferous tubules to biotransform steroids. Similarly, the data support a possible local control of spermatogenesis and spermiogenesis by steroids produced in the Sertoli cells. Testicular mince was incubated for 30 minutes under atmospheric air at 37 'C. Tissues from animals 4 days to 2 years of age were incubated. Both testosterone and androstenedione were recovered from the incubations of all animals, but the production of these androgens showed a progressive increase from 4 to 90 days of age. Incubations from 2-year-old animals produced less androgens than those from 90-day-old animals. In the incubations from the youngest animals (4 to 12 days of age), more tritium than carbon-14 was incorporated into testosterone, but the opposite was true for incubations from older animals. On a per animal basis, the incubations with testicular mince produced 4.5 to 8 times more androgens than teased-tubular preparations from animals of the same age. The changes with age in the amount of TBA-reactive products in testicular homogenates were studied in rats 1 to 90 days of age. The

Mechanisms of aging in relationship to steroid biotransformations and the thiobarbituric acid reactive material in rate testicular tissue in vitro