Open AccessOxidation of Exogenous Lactate by Lactate Dehydrogenase C in the Midpiece of Rat Epididymal Sperm is Essential for Motility and Oxidative Activity
Author(s) -
Hideaki Yamashiro,
Masaaki Toyomizu,
Akane Kadowaki,
Zenya Takeda,
Fumiaki Nakazato,
Natsuki Toyama,
Jin Kobayashi,
Eimei Sato
Publication year - 2009
Publication title -
american journal of applied sciences
Language(s) - English
Resource type - Journals
eISSN - 1554-3641
pISSN - 1546-9239
DOI - 10.3844/ajassp.2009.1854.1859
Subject(s) - sperm , sperm motility , lactate dehydrogenase , motility , capacitation , oxidative phosphorylation , biology , glycolysis , biochemistry , oxygen , andrology , chemistry , metabolism , enzyme , microbiology and biotechnology , medicine , botany , organic chemistry
Problem statement: To identify the metabolic reaction-glycolysis or oxidative phosphorylation that is mainly involved in the production of energy required for rat sperm mobilization. Approach: Epididymal sperm were collected from Wistar rats and extended in lactate-containing or lactate-free raffinose-modified Krebs-Ringer Bicarbonate solution (mKRB)-egg yolk medium supplemented with 0, 1, 2, or 3 mM 2-Deoxy-D-Glucose (2 DG) and 1, 2, or 3 mM sodium Oxamate (OX). Sperm motility, straight-line velocity (VSL) and oxygen consumption were evaluated. Further, immunofluorescent localization of Lactate Dehydrogenase C (LDH-C) in sperm was also performed. Results: Low concentrations of 2DG (1 and 2 mM) did not significantly affect motility, VSL and oxygen consumption of sperm extended in the lactate-containing medium. While sperm motility and oxygen consumption were significantly inhibited by even 1mM 2DG in sperm extended in lactate-free medium. Sperm motility significantly inhibited in the case of sperm extended in lactate-containing and free-medium with 1 mM OX. We also found that sperm motility was not maintained in the absence of lactate throughout the 3 h incubation period. Immunofluorescence study revealed that mainly LDH-C was may be localized in the intramitochondrial region of the sperm. Conclusion: These results suggest that exogenous lactate enhances lactate oxidation by LDH-C, thereby promoting mitochondrial oxidative reactions in the midpiece and maintaining the mobilization of rat epididymal sperm