Expression of aquaporins 7 and 8 in the developing rat testis.

Aquaporin (AQP) is a molecule that facilitates water permeability through cell membranes and is widely distributed in the mammalian body. Among members of the AQP family, AQP7 and AQP8 are predominantly expressed in the testis. This paper examined the expression of these two AQPs in the developing rat testis, using northern blot and immunohistochemistry to visualize their roles during the progression of spermatogenesis in the developing testis. In adult rats, expression of AQP7 was localized to spermatids, whereas AQP8 protein was observed in spermatocytes. In the developing testis, transcripts of AQP7 became detectable between 23 and 25 days post-partum, when round spermatids have been reported to appear. On the other hand, AQP8 mRNA was first detected between 13 and 16 days post-partum, consistent with the reported first appearance of spermatocytes (13-14 days). AQP7 and AQP8 proteins were detectable at 28 days post-partum. The results suggest that AQP7 and AQP8 appear in the testis in accordance with the maturation of germ cells, and are involved in spermatogenesis.