HEXOSE TRANSPORTER EXPRESSION AND FUNCTION IN MAMMALIAN SPERMATOZOA -CELLULAR-LOCALIZATION AND TRANSPORT OF HEXOSES AND VITAMIN-C

We analyzed the expression of hexose transporters in human testis and in human, rat, and bull spermatozoa and studied the uptake of hexoses and vitamin C in bull spermatozoa. Immunocytochemical and reverse tran scription-polymerase chain reaction analyses demonstrated that adult h uman testis expressed the hexose transporters GLUT1, GLUT2, GLUT3, GLU T4, and GLUT5. Immunoblotting experiments demonstrated the presence of proteins of about 50-70 kD reactive with anti-GLUT1, GLUT2, GLUT3, an d GLUT5 in membranes prepared from human spermatozoa, but no proteins reactive with GLUT4 antibodies were detected. Immunolocalization exper iments confirmed the presence of GLUT1, GLUT2, GLUT3, GLUT5, and low l evels of GLUT4 in human, rat, and bull spermatozoa. Each transporter i soform showed a typical subcellular localization in the head and the s perm tail. In the tail, GLUT3 and GLUT5 were present at the level of t he middle piece in the three species examined, GLUT1 was present in th e principal piece, and the localization of GLUT2 differed according of the species examined. Bull spermatozoa transported deoxyglucose, fruc tose, and the oxidized form of vitamin C, dehydroascorbic acid. Transp ort of deoxyglucose and dehydroascorbic acid was inhibited by cytochal asin B, indicating the direct participation of facilitative hexose tra nsporters in the transport of both substrates by bull spermatozoa. Tra nsport of fructose was not affected by cytochalasin B, which is consis tent for an important role for GLUT5 in the transport of fructose in t hese cells. The data show that human, rat, and bull spermatozoa expres s several hexose transporter isoforms that allow for the efficient upt ake of glucose fructose, and dehydroascorbic acid by these cells. J. C ell. Biochem. 71 :189-203, 1998. (C) 1998 Wiley-Liss, Inc.