A polymerase chain reaction (PCR)-based assay was used to evaluate the expression of thyroid hormone receptor β mRNA in Sertoli cells isolated from both prepubertal rat and piglet testes. The expression of an mRNA coding for the functional thyroid hormone receptor β isoform, as established by the PCR assay, agrees with the presence of specific tri-iodothyronine (T3)-binding sites in the Sertoli cell nuclei of both species, as previously evaluated by displacement analysis. The results ratify the existence of a functional T3 receptor in the prepubertal testis and confirm the Sertoli cell as a specific target for thyroid hormone action on the developing testis. On the other hand, in both peripubertal rat (Palmero et al. 1988; Jannini et al. 1990) and piglet (Palmero et al. 1992) testes, high-affinity, low-capacity T3 binding sites have been specifically localised at the Sertoli cell level and TRal mRNA expression has been detected very recently in immature Sertoli cells (Jannini et al. 1994).
The aim of the present work was to test if, in prepubertal Sertoli cells isolated from both immature rat and piglet testes, the expression of an erbAβ mRNA specifically coding for the TR protein could be detected employing an highly sensitive polymerase chain reaction (PCR)-based assay.