title: Utilization of citrate and lactate through a lactate dehydrogenase and ATP-regulated pathway in boar spermatozoa.
abstract: Incubation of boar spermatozoa in Krebs-Ringer-Henseleit medium with either 10 mM lactate or 10 mM citrate induced a fast and robust increase in the intracellular levels of ATP in both cases, which reached a peak after 30 sec of incubation. Utilization of both citrate and lactate resulted in the export of CO(2) to the extracellular medium, indicating that both substrates were metabolized through the Krebs cycle. Incubation with citrate resulted in the generation of extracellular lactate, which was inhibited in the presence of phenylacetic acid. This indicates that lactate is produced through the pyruvate carboxylase step. In addition, there was also a significant increase in tyrosine phosphorylation induced by both citrate and lactate. Boar sperm has a sperm-specific isoform of lactate dehydrogenase (LDH), mainly located in the principal piece of the tail. Kinetic studies showed that boar sperm has at least two distinct LDH activities. The major activity (with an estimated Km of 0.51 mM) was located in the supernatants of sperm extracts. The minor LDH activity (with an estimated Km of 5.9 mM) was associated with the nonsoluble fraction of sperm extracts. Our results indicate that boar sperm efficiently metabolizes citrate and lactate through a metabolic pathway regulated by LDH.
authors.affiliation: Department of Animal Medicine and Surgery, Unit of Animal Reproduction, School of Veterinary Medicine, Autonomous University of Barcelona, Bellaterra, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Medrano
authors.forename: Josep Ma
authors.initials: JM
authors.lastname: Fernández-Novell
authors.forename: Laura
authors.initials: L
authors.lastname: Ramió
authors.forename: Juan
authors.initials: J
authors.lastname: Alvarez
authors.forename: Erwin
authors.initials: E
authors.lastname: Goldberg
authors.forename: Ma
authors.initials: M
authors.lastname: Montserrat Rivera
authors.forename: Joan J
authors.initials: JJ
authors.lastname: Guinovart
authors.forename: Teresa
authors.initials: T
authors.lastname: Rigau
authors.forename: Joan E
authors.initials: JE
authors.lastname: Rodríguez-Gil
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism; D002951:Citrates / Q000378:metabolism* / Q000494:pharmacology; D004789:Enzyme Activation / Q000502:physiology; D019298:Glucose-6-Phosphate / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism* / Q000494:pharmacology; D008297:Male; D010648:Phenylacetates / Q000037:antagonists & inhibitors; D010766:Phosphorylation; D013081:Sperm Motility / Q000187:drug effects / Q000502:physiology; D013082:Sperm Tail / Q000201:enzymology / Q000378:metabolism; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism*; D013552:Swine; D013997:Time Factors; D014443:Tyrosine / Q000187:drug effects / Q000378:metabolism
chemical_list: D002951:Citrates; D007773:Lactates; D010648:Phenylacetates; D002245:Carbon Dioxide; D014443:Tyrosine; D019298:Glucose-6-Phosphate; D000255:Adenosine Triphosphate; D006003:Glycogen; D007770:L-Lactate Dehydrogenase; C025136:phenylacetic acid