Microtubules are oriented with their minus-ends directed apically before tight junction formation in rat Sertoli cells.

We have examined the polarity of microtubules in Sertoli cells of the seminiferous epithelium during testicular development to test the hypothesis that microtubules change their polarity during tight junction formation. Microtubules in a number of polarized epithelial cells, including Sertoli cells, are oriented with their minus-ends directed toward the apical surface of the cell. Indirect evidence from cultured epithelial cell models suggests that this orientation may be achieved during the relocation of centrioles, reorganization of microtubules, and repositioning of the Golgi that occurs during tight junction formation. Using the microtubule hook decoration technique, we have determined the polarity of Sertoli cell microtubules at 5 and 15 days postnatally, prior to the establishment of the tight junctional complex of the blood testis barrier at 19 days. Our results indicate that, although centrioles and the Golgi apparatus migrate from an infranuclear location at 5 days to a supranuclear location by 15 days, the minus-ends of microtubules are already directed toward the apical surface of the cell by 5 days of age. These data indicate that the establishment of the apically directed minus-end orientation of microtubules of mature Sertoli cells precedes rearrangement of the centrioles and Golgi and is not temporally related to the formation of the tight junctional complex of the blood testis barrier.