Substrates for endogenous metabolism by mature boar spermatozoa

Washed boar spermatozoa incubated in the absence of exogenous substrates ma intained a high energy charge potential (ECP) for at least 10 h. Addition o f bromopyruvate, an inhibitor of stage 2 of the glycolytic pathway, at any time during the incubation caused an immediate decrease in the ECP, indicat ing that the mobilization of endogenous compounds requires this section of the pathway for the production of lactate, the major mitochondrial substrat e for ATP production. Some of the sources of the metabolic substrates have been identified, by NMR and metabolic studies, as di- or triglycerides, to produce glycerol, and membrane phospholipids for the production of glycerol 3-phosphate. Acetylcarnitine contributes acetyl groups early in the incuba tion; glycerylphosphorylcholine is degraded to glycerol 3-phosphate and cho line after about 5 h, and acetate also accumulates after about 5 h. The pre sence of phosphorylcholine and phosphorylethanolamine later in the incubati on indicates that phospholipids are also degraded to glycerol.