Fig. 2

Model for compartmentalized iron transport in the testis. The seminiferous tubule (SFT) is partially protected from systemic iron overload. Here is a model of testis showing the anatomy of interstitial tissue and SFT, where male germ cell development proceeds from the SFT basal membrane (BM) to the SFT lumen (Lu). SC, Sertoli cell; SG, spermatogonia; PLS, preleptotene spermatocyte; PCS, pachytene spermatocyte; RS, round spermatid; ES, elongated spermatid. Three SC and their immediate surroundings are shown. Iron transport across the SFT basal membrane is very limited. Within the SFT some SG and mainly primary spermatocytes acquire iron-loaded ferritin from SC, and upon maturation elongating spermatids return iron to the SC, which traffic it back to a new generation of spermatocytes. Obligatory iron losses through spermatozoa that leave the testis are replenished by the peripheral circulation through the transferrin-TfR-1 system. Ferroportin likely plays its main role in iron trafficking across the interstitial space, where selective barriers at the smooth muscle cells of blood vessels and the peritubular myoid cells provide the male germ cells with additional protection from the periphery. RB, residual body. (From [17])