title: Studies in vitro on shuttle systems of mouse spermatozoa.
abstract: Observations on systems reconstituted in vitro with different starting substrates (2-hydroxy-acids, 2-oxo-acids or leucine) indicate that a branched-chain 2-hydroxy-acid/2-oxo-acid shuttle for the transfer of reducing equivalents from cytosol to mitochondria may be operational in mouse sperm. Evidence is presented suggesting that the 2-oxo-acids produced by intramitochondrial oxidation of 2-hydroxy-acids ingressed from the cytosol can recycle back into the external phase. Observations in vitro demonstrate that, in addition to the branched-chain 2-hydroxy-acid/2-oxo-acid shuttle, the malate/aspartate system is also active in mouse sperm. On the contrary, the lactate/pyruvate redox couple does not appear to function as part of a shuttle system in mouse sperm mitochondria. The glycerol 3-phosphate shuttle probably is not functionally significant in mouse spermatozoa, since the activity of the 'soluble' glycerol 3-phosphate dehydrogenase is very low.
mesh_terms: D000818:Animals; D006880:Hydroxy Acids / Q000378:metabolism*; D066298:In Vitro Techniques; D007651:Keto Acids / Q000378:metabolism*; D007656:Ketoglutaric Acids / Q000378:metabolism; D007930:Leucine / Q000378:metabolism; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D013094:Spermatozoa / Q000378:metabolism*
chemical_list: D006880:Hydroxy Acids; D007651:Keto Acids; D007656:Ketoglutaric Acids; D009243:NAD; C013082:alpha-ketoisocaproic acid; D007930:Leucine