Synthesis and metabolism of steroids is highly interconnected within a tissue.  The initial objective of these studies was to evaluate the influence of estrogens on the synthesis and metabolism of other steroids in the testis and other tissues.  The aromatase inhibitor, letrozole, was used to inhibit testicular estrogen synthesis.  Littermates from five different litters (potentially six boars from one litter) provided the testis, prostate, and liver tissues but only four boars (one from each of four litters) were evaluated at each age in the vehicle-treated group and compared with their respective littermates in the letrozole-treated group.  Surprisingly, androgens were not significantly altered even though testicular estrogens were dramatically reduced by treatment.  Free estrogens were not significantly altered in the prostate although estrogen sulfates were reduced prostates from the letrozole-treated boars compared with their vehicle-treated littermates. Aromatase enzymatic activity was detectable but very low in the prostate.  Gene expression for steroid sulfatase (STS) was readily detectable in the prostate, testis, and liver. Together, the data suggest steroid sulfates may serve as a reservoir for tissue-specific steroid regulation.

 Six littermate boars were randomly assigned to letrozole treatment (0.1 mg/kg body weight) or vehicle treatment (canola oil).  Tissues from one pair of boars (one letrozole-treated littermate and one vehicle-treated littermate) were harvested at 16 weeks of age (final treatment at 15 weeks of age of for age group).  Tissues from a second pair of boars from the same litter were harvested at 20 weeks of age and tissues from the final pair of littermate boars was harvested at 40 weeks of age.  Boars from 5 different litters (30 boars) were treated as described.  Tissues from 24 boars contributed to these studies using mass spectrometry to analyze tissue steroid levels.  Following euthanasia, testis, prostate, and liver tissues were flash-frozen on dry ice and stored at -80^oC until analysis.  Treatment details and additional physiological measurements are available (1, 2).

1.            Berger T, Kentfield L, Roser JF, Conley A. Stimulation of Sertoli cell proliferation: defining the response interval to an inhibitor of estrogen synthesis in the boar. Reproduction. 2012;143(4):523-9.

2.            Berger T, Conley AJ. Reducing endogenous estrogen during prepuberal life does not affect boar libido or sperm fertilizing potential. Theriogenology. 2014;82(4):627-35.

Four of the five littermate pairs were available for analysis at each time point.