title: Lactate dehydrogenase-C4 is involved in heparin- and NADH-dependent bovine sperm capacitation.
abstract: Lactate dehydrogenase C4 isoenzyme (LDH-C4) is involved in the energy metabolism of spermatozoa. Sperm capacitation is considered part of an oxidative process; an NADH oxidase of plasma membrane could be responsible for superoxide anion generation which is required for capacitation. The role of LDH-C4 and the requirements of NADH in cryopreserved bovine sperm capacitation were studied. LDH-C4 activity was 5.52 +/- 3.41, 15.72 +/- 6.04 and 15.22 +/- 1.92 Units 1010 spermatozoa-1 in plasma membrane, sperm suspension and cytosol fraction, respectively; these activities were inhibited by sodium oxamate. To study the influence of oxidative substrates in capacitation, three different TALP (T) media were used: TP (pyruvate); TL (lactate) and TC (citrate); heparin or NADH was then added. There were no significant differences in the percentage of capacitation induced by heparin or NADH in TALP medium; similar levels of capacitation were achieved with TL alone or TL +heparin and TP +NADH; capacitation was inhibited with sodium oxamate in all treatments used. Cytosolic NADH may be required as a substrate for sperm oxidase. Lactate influx through plasma membrane may be utilized by cytosolic LDH-C4, increasing reduced coenzymes required for capacitation. Plasma membrane LDH-C4 may participate in the production of lactate to obtain intracellular reducing equivalents to be used by sperm oxidase for in vitro sperm capacitation.
authors.affiliation: Area de Química Biológica, Facultad de Ciencias Veterinarias, Universidad de Buenos Aires, Argentina.
authors.forename: C M
authors.initials: CM
authors.lastname: O'Flaherty
authors.forename: N B
authors.initials: NB
authors.lastname: Beorlegui
authors.forename: M T
authors.initials: MT
authors.lastname: Beconi
mesh_terms: D000818:Animals; D002208:Caproates / Q000378:metabolism; D002417:Cattle; D005229:Fatty Acids, Monounsaturated / Q000378:metabolism; D006493:Heparin / Q000378:metabolism*; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008297:Male; D009243:NAD / Q000378:metabolism*; D013075:Sperm Capacitation / Q000187:drug effects / Q000502:physiology*; D013094:Spermatozoa / Q000201:enzymology* / Q000502:physiology; D013379:Substrate Specificity
chemical_list: D002208:Caproates; D005229:Fatty Acids, Monounsaturated; D007527:Isoenzymes; D009243:NAD; C017452:2-keto-4-pentenoic acid; C001916:alpha-ketocaproic acid; D006493:Heparin; D007770:L-Lactate Dehydrogenase; C409673:lactate dehydrogenase C4