Ontogenetic profile of the expression of thyroid hormone receptors in rat and human corpora cavernosa of the penis.
Abstract
The spatiotemporal distribution of mRNA for the thyroid hormone nuclear receptors (TR) alpha1, alpha2 and beta in the penis and smooth muscle cells (SMCs) of the corpora cavernosa of rats and humans was studied during development. TRalpha1 and TRalpha2 were found expressed in the penis and in SMCs during ontogenesis without development-dependent changes.
Contrary to that, TRbeta showed an increase from 3 to 6 days post natum (dpn) to 20 dpn, remaining high in adulthood. The same expression profile was observed in humans.
These results have been confirmed by immunohistochemistry localization in SMCs and endothelial cells of the corpora cavernosa. While the expression of TRbeta is strictly regulated by development, TRalpha1 is the principal isoform present in corpora cavernosa, suggesting its importance in SMC function.
Thus, the presence of TRs in the penis provides the biological basis for the direct action of thyroid hormones on this organ.