title: A calorimetric method to assess endogenous metabolism and its application to the study of bovine sperm.
abstract: Calorimetry was used to assess the importance of endogenous metabolism towards total ATP synthesis in bovine sperm in the presence of extracellular glucose. Sperm were incubated in the calorimeter with D-[U-14C]glucose without or with electron transport inhibitors, rotenone and antimycin A. Steady-state heat production during the incubations was measured for 30 min, the incubations were terminated, and the cell suspensions removed for analysis of radioactive glucose and its metabolic end-products. Heat production (mean +/- S.E.) associated with the metabolism of glucose was calculated, from enthalpies of formation of glucose and its end-products, as -412 +/- 34 mJ/h/10(8) cells in control incubations and -263 +/- 18 mJ/h/10(8) cells in the incubations with electron transport inhibitors. Measured heat production was -455 +/- 36 and =263 +/- 17 mJ/h/10(8) cells, respectively. Thus, heat production by endogenous pathways, the difference between measured total heat production and calculated exogenous heat production, was -43 +/- 14 mJ/h/10(8) cells for control cells and about -6 mJ/h/10(8) cells for inhibited cells. The ratio of heat produced per mol of ATP synthesized is similar for all ATP-producing pathways. Therefore, about 10% of total ATP synthesis in control cells and less than 2% in inhibited cells is provided by endogenous pathways when extracellular glucose is present.
mesh_terms: D000085:Acetates / Q000378:metabolism; D000108:Acetylcarnitine / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000963:Antimetabolites / Q000494:pharmacology; D002151:Calorimetry / Q000379:methods*; D002417:Cattle; D004734:Energy Metabolism; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008297:Male; D013094:Spermatozoa / Q000378:metabolism*; D013997:Time Factors
chemical_list: D000085:Acetates; D000963:Antimetabolites; D007773:Lactates; D019344:Lactic Acid; D000108:Acetylcarnitine; D000255:Adenosine Triphosphate; D005947:Glucose