Abstract: 66

EXPRESSION OF STEROIDOGENIC ENZYMES IN BOAR TESTIS DURING POSTNATAL DEVELOPMENT.

Serdia Mack^{1 *}, Wesley Garrett^{2 *}, H. David Guthrie^{2 *}
Department of Physiology and Biophysics, Howard University College of Medicine, Washington, DC. ¹
Germplasm and Gamete Physiology Laboratory, ARS, USDA, Beltsville, MD. ²

Paraffin sections of testis were prepared for immunohistochemical analysis of steroidogenic enzyme expression at 3, 5, 10, 16, and 25 weeks postpartum (n=3). The most notable changes in plasma testosterone and testis weight occurred between 16 and 25 weeks when they increased (p< .05) by 88 and 87%, respectively, from 6 to 49 ng/ml and from 76 to 534 g. Puberty was indicated at 25 weeks by the presence of spermatozoa in 80% of tubules. Expression of Ki67 (a marker for cell proliferation) showed massive proliferation of Leydig cells between 3 and 10 weeks. Cytochromes P450 side chain cleavage (P450_scc), 17a-hydroxylase/17,20 lyase (P450₁₇) and aromatase (P450 arom) were localized exclusively in Leydig cells with cytoplasmic staining. P450_scc and P450₁₇ immunostaining were of high intensity and dispersed throughout the interstitium with a transient decrease in staining intensity at 7 and 10 weeks of age, respectively. The intensity of P450 arom expression and the number of immunoreactive cells was low through 10 weeks and then they increased through 25 weeks. The number of Leydig cells staining for 3HSD was limited, appearing just beneath the capsule of the testis, and in small groups of Leydig cells adjoining the rete testis. At 16 and 25 weeks, small clusters of Leydig cells located adjacent to and surrounding interstitial blood vessels also stained for 3HSD. These findings show that the major testicular steroidogenic enzymes are localized in Leydig cells and they are continuously expressed during the time of rapid testicular growth. The unique pattern and limited expression of 3HSD provides further evidence for the Δ ⁵ steroidogenic pathway being predominant in the boar testis.

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.