Abstract: 65

THYROID HORMONE AND LEYDIG CELL REGENERATION IN THE ADULT RAT.

H.B.S. Ariyaratne¹ , S.M.L.C. Mendis-Handagama^{1 *}, N. Mills^{2 *}, J.I. Mason^{3 *}
College of Vet Medicine, The University of Tennessee, Knoxville, Tennessee ¹
Dept of Biolo, Texas Woman's University, Denton, Texas ²
Royal Infirmary of Edinburgh NHS Trust, Edinburgh, Scotland ³

In the present study, we tested whether thyroid hormone regulates Leydig cells (LC) regeneration in the adult rat testis after EDS treatment. Three groups of 90 day old Sprague Dawley rats (n=32/gp) were injected i.p. with EDS (75mg/kg) to destroy LC. Beginning from day 1 of EDS administration rats in groups I (hyperthyroid), II (hypothyroid) and III (controls) received daily s.c. injections of triiodothyronine (T₃, 100µg/kg), 0.1% propyl thiouracil (PTU) in drinking water and daily s.c. injections of saline, respectively. Testing was done at days 2, 7, 14 and 21. Blood samples were collected from these rats (n=8/group) and thyroid hormone levels were determined by radioimmunoassay. One testis of each rat was fixed by either perfusion with 2.5% glutaraldehyde in cacodylate for stereology (n=5/gp) or by immersion in Bouins for immunocytochemistry (n=3/gp) for 3hydroxysteroid dehydrogenase (3HSD). The other testis was used in in vitro testicular incubations and media were stored for future analyses for androgens. Serum T₃ were in agreement with the hyperthyroid, hypothyroid and euthyroid status of rats in groups I, II and III, respectively. LC were absent in hypothyroid rats at all ages and at days 2, 7 and 14 in control and hyperthyroid rats. LC number per testis was doubled in hyperthyroid rats compared to controls at day 21. 3HSD (marker for LC) immunocytochemistry results were in agreement with these observations. Mesenchymal cell (LC precursors) number per testis was similar in all treatment groups on days 2 and 7. However, at days 14 and 21 they were different among the three groups; highest in hypothyroid rats and lowest in hyperthyroid rats. Data demonstrated that hypothyroidism inhibits LC regeneration after EDS treatment and hyperthyroidism results in more precursor cell differentiation into Leydig cells.

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