title: Activation of sea-urchin sperm motility is accompanied by an increase in the creatine kinase exchange flux.
abstract: The kinetics of the creatine kinase (CK) reaction were studied in suspensions of quiescent and active, intact sea-urchin spermatozoa in artificial seawater, using 31P-NMR magnetization transfer. In inactive sperm, no CK-mediated exchange flux was detected, whereas in activated motile sperm, the forward pseudo-first-order rate constant was 0.13+/-0.04 s-1 at 10 degrees C, corresponding to a steady-state CK flux of 3.1+/-0.5 mM.s-1. Intracellular pH shifted from 6.6+/-0.1 to 7.6+/-0.1 upon activation. The phosphocreatine (PCr)/ATP and PCr/Pi ratios were only marginally reduced in activated sperm, whereas the estimated cytosolic free ADP concentration increased remarkably from 9 microM in quiescent, to 114 microM in activated spermatozoa. The elevation of CK flux upon sperm activation is discussed in the light of the proposition that in sea-urchin spermatozoa, which are fuelled entirely by oxidative phosphorylation, high-energy phosphate transport is mediated by a 'CK/PCr shuttle'.
authors.affiliation: Department of in vivo NMR Spectroscopy, Bijvoet Center for Biomolecular Research, Utrecht University, Bolognalaan 50, NL-3584 CJ Utrecht, The Netherlands.
authors.forename: F A
authors.initials: FA
authors.lastname: Dorsten
authors.forename: M
authors.initials: M
authors.lastname: Wyss
authors.forename: T
authors.initials: T
authors.lastname: Wallimann
authors.forename: K
authors.initials: K
authors.lastname: Nicolay
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D003401:Creatine / Q000378:metabolism; D003402:Creatine Kinase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D010085:Oxidative Phosphorylation; D010710:Phosphates / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism; D012617:Sea Urchins; D013081:Sperm Motility; D013094:Spermatozoa / Q000201:enzymology*; D013696:Temperature
chemical_list: D010710:Phosphates; D010725:Phosphocreatine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D003402:Creatine Kinase; D003401:Creatine