title: Alterations of oxygen uptake and the redox state of ubiquinone in rabbit sperm exposed to a variety of physiologic treatments.
abstract: The rate of TEMPONE reduction by electrons originating from ubiquinone in intact rabbit spermatozoa was observed for control, high ionic strength (HIS) medium-treated, and HIS-seminal plasma-treated (HIS-SP) samples. The presence of TEMPONE in the incubation medium had no effect on oxygen consumption, demonstrating the utility of TEMPONE as a nonperturbing probe of the ubiquinol redox state. The rate of TEMPONE reduction was significantly increased over control levels for sperm incubated in hypertonic medium and was correlated to a decrease in oxygen consumption and a relative increase in ATP in the total adenine nucleotide pool. This increase in TEMPONE reduction in HIS sperm was reversed by treatment of sperm with seminal plasma, but seminal plasma had no effect on oxygen consumption or relative amounts of ATP in the adenine nucleotide pool. These observations are consistent with state 3 respiration in control sperm and state 4 respiration in HIS- and HIS-SP-treated sperm. Arrhenius data were obtained for ejaculated and epididymal sperm subjected to a variety of treatments. Lines fitted to plots of Arrhenius data revealed that each treatment affected the activation energy and intercept relative to controls. Evidence is presented for a phase transition occurring at 13 degrees C based on changes in the rate of TEMPONE reduction by ubiquinol. It was noted that, above the phase transition, rate constants for the reaction were dependent upon both treatment and temperature, but below the transition the differential effects of treatment were no longer apparent. The present study has demonstrated that events taking place in the respiratory chain can be closely monitored by measuring oxygen uptake and TEMPONE reduction, and that these events are affected by alterations in the sperm environment.
mesh_terms: D000818:Animals; D007700:Kinetics; D008297:Male; D009994:Osmolar Concentration; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011817:Rabbits; D012661:Semen / Q000502:physiology*; D013094:Spermatozoa / Q000378:metabolism*; D013816:Thermodynamics; D014216:Triacetoneamine-N-Oxyl; D014451:Ubiquinone / Q000378:metabolism*
chemical_list: D014451:Ubiquinone; D014216:Triacetoneamine-N-Oxyl