Submission Number: CHA-4-12-2

Abstract Number: 320

THYROID AND LUTEINIZING HORMONES ON THE ONSET OF LEYDIG PRECURSOR CELL DIFFERENTIATION.

HB Siril Ariyaratne* ¹, SML Chamindrani Mendis-Handagama* ¹ and J Ian Mason* ²

Dept. of Animal Science, The University of Tennessee, Knoxville, TN, U.S.A. ¹
Dept. of Reproductive and Developmental Sciences, University of Edinburgh Royal Infirmary, Edinburgh, U. K. ²

Abstract:
We tested the effects of thyroid hormone and luteinizing hormone (LH) on the onset of mesenchymal cell (MC) differentiation into adult Leydig cells (ALC) in the prepubertal rat testis. Four groups of Sprague Dawley rats were used; groups 1, 2 and 3 received daily SC injections of saline (200 l, controls), triiodothyronine (T₃ 50 g/kg b. wt.) and LH (ovine LH 10 g/rat/day), respectively from birth. Group 4 rats were made hypothyroid from birth by adding 0.1% propylthiouracil (PTU) to their mother's drinking water. From all groups, testes were prepared for immunocytochemistry at days 712, 16, and 21. Avidin biotin method was used to immunolocalize 3hydroxysteroid dehydrogenase (3HSD) and LH receptors (LHR) in testis tissue. In control rats, out of all spindleshaped cells in the testis interstitium, only the peritubular MC showed +ve immunolabeling for 3HSD beginning from day 11, and LHR was first detected in these cells at day 12. In T₃ rats, 3HSD and LHR +ve spindleshaped cells were first observed on days 9 and 11, respectively; they were exclusively the peritubular MC. 3HSD and LHR +ve spindleshaped cells were absent in the testis interstitium of LH injected rats from days 712, but was present at day 16. Also, more FLC clusters and FLC in mitosis were present in LH treated rats compared to rats in all other treatment groups. The number of positive cells for each protein continued to increase thereafter in these 3 groups. In PTU rats, 3HSD and LHR +ve spindleshaped cells were absent at all stages. These findings suggest that, 1) the precursor cells for the ALC in the postnatal rat testis are the peritubular MC, 2) LH is not required for the onset of MC differentiation into ALC; it delays the process, 3) LH treatment causes increase in FLC clusters, and 4) thyroid hormone is critical to the onset of MC differentiation into ALC.

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This abstract is being presented at: 8:00 AM in session:
Gonadal Function