title: Futile substrate cycles in the glycolytic pathway of boar and rat spermatozoa and the effect of alpha-chlorohydrin.
abstract: In boar spermatozoa incubated with 0.1 mM-glucose about 20 nmol glucose were converted to lactate and CO2 and the rate of futile substrate cycling between glucose and glucose 6-phosphate was about 6 nmol/10(8) spermatozoa/30 min. Futile cycling was increased in the presence of 0.05 or 1 mM-alpha-chlorohydrin but not to an extent sufficient to account for the rapid decline in ATP concentration observed under these conditions. These estimates include a substantial rate of fructose formation from fructose phosphates. The addition of 10 mM-L-lactate plus 1 mM-pyruvate protected the spermatozoa against the effect of alpha-chlorohydrin and glucose on the ATP concentration but increased futile substrate cycling. Substrate cycling between fructose 6-phosphate and fructose 1,6-bisphosphate could not be measured in boar spermatozoa but in rat spermatozoa its rate (nmol/10(8) spermatozoa/30 min) was about 10 under control condition and about 25 in the presence of 1 mM-alpha-chlorohydrin. This increase was insufficient to account for the decline in ATP concentration. In both species futile substrate cycling consumed a significant proportion of the ATP synthesis during lactate production but only about 5% of that produced in the oxidation of glucose to acetyl carnitine and CO2.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002728:Chlorohydrins / Q000494:pharmacology*; D005635:Fructosediphosphates / Q000378:metabolism; D005636:Fructosephosphates / Q000378:metabolism; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000378:metabolism; D006019:Glycolysis / Q000187:drug effects*; D008297:Male; D051381:Rats; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism*; D013552:Swine; D013997:Time Factors; D000517:alpha-Chlorohydrin / Q000494:pharmacology*
chemical_list: D002728:Chlorohydrins; D005635:Fructosediphosphates; D005636:Fructosephosphates; D005958:Glucosephosphates; D019298:Glucose-6-Phosphate; C027618:fructose-6-phosphate; D000255:Adenosine Triphosphate; D000517:alpha-Chlorohydrin; D005947:Glucose; C029063:fructose-1,6-diphosphate