Effects of calcium ions on the malate-aspartate shuttle in slow-cooled boar spermatozoa.
The effects of intracellular free calcium (Ca2+) ions on the malate-aspartate shuttle were studied in slow-cooled boar spermatozoa. The capacity of the malate-aspartate shuttle was assessed by an indirect method on the basis of accumulation of lactate relative to pyruvate when ethanol is provided as substrate. The capacity of the malate-aspartate shuttle at 37 degrees C was dependent on the presence of Ca2+ ions and was stimulated by an influx of Ca2+ ions induced by the combination of the Ca2+ ionophore A23187 and 100 microM CaCl2. When washed spermatozoa were cooled slowly to 15 degrees C, the percentage of progressive motile spermatozoa was about half that at 37 degrees C in 100 microM Ca(2+)-containing medium, while the capacity of the malate-aspartate shuttle remained equal to that at 37 degrees C. The motility decreased further at higher concentrations of Ca2+ ions. Spermatozoa in EGTA-containing medium barely moved at 15 degrees C and the capacity of the malate-aspartate shuttle decreased. Even in Ca(2+)-containing medium, LaCl3 caused a decrease in the capacity of the malate-aspartate shuttle at 15 degrees C. These results suggest that an influx of a low concentration of Ca2+ ions activates the malate-aspartate shuttle at 15 degrees C, with a subsequent increase in the proportion of cells that maintain progressive motility.
Nara Prefectural Livestock Experiment Station, Japan.
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Nishimura
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D003080:Cold Temperature; D004533:Egtazic Acid / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology; D007811:Lanthanum / Q000494:pharmacology; D008293:Malates / Q000378:metabolism*; D008297:Male; D013081:Sperm Motility / Q000187:drug effects; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism*; D013552:Swine
D008293:Malates; D001224:Aspartic Acid; D000001:Calcimycin; D000431:Ethanol; D004533:Egtazic Acid; D000244:Adenosine Diphosphate; D007811:Lanthanum; C030298:malic acid; D000255:Adenosine Triphosphate; D002118:Calcium