Molecular identification and functional characterization of the vitamin C transporters expressed by Sertoli cells

Abstract

Vitamin C is an essential micronutrient for the development of male germ cells. In the gonad, the germ cells are isolated from the systemic circulation by the blood-testis barrier, which consists of a basal layer of Sertoli cells that communicate through an extensive array of tight junction complexes. To study the behavior of Sertoli cells as a first approach to the molecular and functional characterization of the vitamin C transporters in this barrier, we used the 42GPA9 cell line immortalized from mouse Sertoli cells. To date, there is no available information on the mechanism of vitamin C transport across the blood-testis barrier. This work describe the molecular identity of the transporters involved in vitamin C transport in these cells, which we hope will improve our understanding of how germ cells obtain vitamin C, transported from the plasma into the adluminal compartment of the seminiferous tubules. RT-PCR analyses revealed that 42GPA9 cells express both vitamin C transport systems, a finding that was confirmed by immunocytochemical and immunoblotting analysis. The kinetic assays using radioactive vitamin C revealed that both ascorbic acid (AA) transporters, SVCT1 and SVCT2, are functionally active. Moreover, the kinetic characteristics of dehydroascorbic acid (DHA) and 3-methylglucose (OMG) transport by 42GPA9 Sertoli cells correspond to facilitative hexose transporters GLUT1, GLUT2 and GLUT3 expressed in these cells. This data is consistent with the concept that Sertoli cells have the ability to take up vitamin C. It is an important finding and contributes to our knowledge of the physiology of male germ cells.