Follicular Development in Rabbits After Active Immunization to Testosterone

Abstract

<p>The role of testosterone in follicular development and ovulatIon has been investigated by immunizing female rabbits to testosterone-3-bovine serum albumin (T-3-BSA). The intent of this procedure was to render any endogenously produced testosterone inactive by means of its high affinity binding to specific antibody.</p> <p>In order to determine the time course of the effects of this procedure three groups of 12 - 6 control, 6 experimental - immaturely immunized rabbits were sacrificed at 5, 8 and 11 weeks after immunization. The effects observed at 11 weeks were compared with a group of 10 - 6 control, 4 experimental - maturely immunized rabbits sacrificed after the same length of immunization. In addition a group of 11 - 5 control, 6 experimental - immaturely immunized animals were mated to a proven male 14 weeks after immunization.</p> <p>Animals were boosted regularly and the antiserum titer followed weekly. Blood samples were taken weekly for the determination of FSH and LH levels and the total and percent bound testosterone and estradiol. After sacrifice the ovaries and uteri were removed for histology. Follicular development was examined and the maximum follicular diameter ≥ 1.0 mm and ≥ 1.5 mm was recorded. In mated animals the number of corpora lutea per ovary were counted.</p> <p>SignifIcant antiserum titers to testosterone were observed in all experimental rabbits by 5 weeks of immunization. Over the 14 weeks of the experiment values ranged from 1:700 to 1:52,000.</p> <p>In control rabbits serum testosterone values were less than 0.5 ng/ml while values in experimental rabbits rose steadily over the length of the experiment (group values ranged from 0.6 ± 0.1 ng/ml to 2.1 ± 0.9 ng/ml, 2.2 ± 0.7 ng/ml to 5.7 ± 0.8ng/ml and 4.4 ± 1.2 ng/ml to 6.8 ± 1.2 ng/ml at 5,8 and 11 weeks respectively). Testosterone binding in control animals remained in the 93% to 95% range throughout the experiment while in experimental animals testosterone binding increased significantly to approximately 99% at 5 weeks of immunization and remained constant thereafter.</p> <p>Estradiol values in control rabbits remained relatively constant throughout the ewperiment (group range: 50.7 ± 5.4 pg/ml to 81.8 ± 4.9 pg/ml). A consistent and significant increase in estradiol occurred in experimental animals (group values ranged from 69.5 ± 15.4 pg/ml to 88.5 ± 8.7 pg/ml, 74.5 ± 9.8 pg/ml to 118.5 ± 13.1 pg/ml and 81.6 ± 6.9 pg/ml to 157 ± 30.3 pg/ml at 5,8 and 11 weeks after immunization. Prior to immunization estradiol binding in experimental rabbits was not different from control values (range : 83% to 88%). There was a significant increase in estradiol binding by 5 weeks of immunization in the experimental groups (range: 89.4% to 94.5%). By 11 weeks estradiol binding increased to as much as 97.9%.</p> <p>Follicular development was abnormal in T-3-BSA immunized rabbits. The ovaries contained numerous large cystic and hemorrhagic follicles. At 8 weeks experimental ovaries contained more follicles ≥1.0 mm (27.2 ± 3.1 versus 15.3 ± 2.9, p < 0.01) and ≥1.5 mm (5.83 ± 1.7 versus 0.42 ± 0.2, p < 0.005). At 11 weeks there were more follicles ≥ 1.5 mm in both immature (5.0 ± 0.9 versus 0.92 ± 0.31, p < 0.001) and mature (7.25 ± 0.92 versus 4.17 ± 0.74, p < 0.05) experimental ovaries. Increased vascularization, some thecal cell hypertrophy, and marked interstitial cell hypertrophy were characteristic of the experimental ovaries. There was also a significant increase in the number of ovulations in the experimental rabbits (8.0 ± 2.1 versus 4.4 ± 1.9, p < 0.005).</p> <p>Immunization of female rabbits to testosterone is a useful tool for the study of hormone interactions in the regulation of follicular development and ovulation. In addition it may serve as a useful model for the study of the processes involved in the development of cystic ovaries.</p>