title: Kinetics, molecular basis, and differentiation of L-lactate transport in spermatogenic cells.
abstract: Round spermatid energy metabolism is closely dependent on the presence of L-lactate in the external medium. This L-lactate has been proposed to be supplied by Sertoli cells in the seminiferous tubules. L-Lactate, in conjunction with glucose, modulates intracellular Ca(2+) concentration in round spermatids and pachytene spermatocytes. In spite of this central role of L-lactate in spermatogenic cell physiology, the mechanism of L-lactate transport, as well as possible differentiation during spermatogenesis, has not been studied in these cells. By measuring radioactive L-lactate transport and intracellular pH (pH(i)) changes with pH(i) fluorescent probes, we show that these cells transport L-lactate using monocarboxylate-H(+) transport (MCT) systems. RT-PCR, in situ mRNA hybridization, and immunocyto- and immunohistochemistry data show that pachytene spermatocytes express mainly the MCT1 and MCT4 isoforms of the transporter (intermediate- and low-affinity transporters, respectively), while round spermatids, besides MCT1 and MCT4, also show expression of the MCT2 isoform (high-affinity transporter). These molecular data are consistent with the kinetic data of L-lactate transport in these cells demonstrating at least two transport components for L-lactate. These separate transport components reflect the ability of these cells to switch between the generation of glycolytic L-lactate in the presence of external glucose and the use of L-lactate when this substrate is available in the external environment. The supply of these substrates is regulated by the hormonal control of Sertoli cell glycolytic activity.
authors.affiliation: Instituto de Química, Pontificia Universidad Católica de Valparaíso, Casilla 4059, Valparaíso, Chile.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Brauchi
authors.forename: Maria C
authors.initials: MC
authors.lastname: Rauch
authors.forename: Ivan E
authors.initials: IE
authors.lastname: Alfaro
authors.forename: Christian
authors.initials: C
authors.lastname: Cea
authors.forename: Ilona I
authors.initials: II
authors.lastname: Concha
authors.forename: Dale J
authors.initials: DJ
authors.lastname: Benos
authors.forename: Juan G
authors.initials: JG
authors.lastname: Reyes
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D017403:In Situ Hybridization; D019344:Lactic Acid / Q000378:metabolism*; D008297:Male; D027501:Monocarboxylic Acid Transporters / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012708:Sertoli Cells / Q000166:cytology / Q000378:metabolism*; D013087:Spermatids / Q000166:cytology / Q000378:metabolism; D013091:Spermatogenesis / Q000502:physiology*; D013737:Testis / Q000166:cytology / Q000378:metabolism
chemical_list: D027501:Monocarboxylic Acid Transporters; D020033:Protein Isoforms; D019344:Lactic Acid