Oxidation of Exogenous Lactate by Lactate Dehydrogenase C in the Midpiece of Rat Epididymal Sperm is Essential for Motility and Oxidative Activity
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.
Copyright: © 2009 Hideaki Yamashiro, Masaaki Toyomizu, Akane Kadowaki, Zenya Takeda, Fumiaki Nakazato, Natsuki Toyama, Jin Kobayashi and Eimei Sato. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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- mitochondrial oxidative reaction
- rat epididymal sperm