Peroxisome proliferator-activated receptor α (PPARα), a member of the steroid hormone receptor superfamily, has been linked to lipid homeostasis and tumorigenesis in tissues with high expression of receptor protein. On the other hand, the role of PPARα in tissues with a lower expression is not well known. Here we demonstrate the localization of PPARα messenger RNA (mRNA) and protein in developing and adult rat testis. Additionally, we demonstrate the expression of PPARα protein in adult human testis. Our experiments with Northern analysis, in situ hybridization and immunocytochemistry reveal a complex distribution of PPARα in tubular and interstitial cells of both adult and developing rat testis. The overall expression is rather low but may be modified by exogenous or endogenous stimuli. An up-regulation of PPARα mRNA could be observed after stimulation with FSH. In the developing rat testis, a clear expression of PPARα mRNA was present from the first days after birth. Additionally, PPARα mRNA and protein increased toward adulthood. In adult human testis PPARα immunoreactivity (IR) was present in interstitial Leydig cells and tubular cells. In the seminiferous epithelium of adult human testis the expression of PPARα-IR could be seen in meiotic spermatocytes, spermatids and myoid peritubular cells. The findings of our study suggest that PPARα may be involved in the regulation of growth and differentiation of tubular and interstitial cells in rat and human testis.
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