Inhibition of Respiration in Sea Urchin Spermatozoa Following Interaction with Fixed Unfertilized Eggs V. Inhibition of Electron Transport in a Span of Mitochondrial Respiratory Chain between Cytochrome b and Cytochrome c in Sea Urchin Spermatozoa, Induced by the Interaction with Glutaraldehyde Fixed Eggs: (sea urchin/sperm/respiration/cytochrome/egg-sperm interaction).

In the sea urchin, Anthocidaris crassispina, α and γ peaks of reduced cytochrome b were distinctly observed but no peaks of cytochrome a and cytochrome c were found in the difference spectra between H O oxidized and the aerobic suspensions of the immotile spermatozoa, which were obtained by an incubation of the suspension of spermatozoa and the glutaraldehyde-fixed eggs for 15 min at 20°C. A similar profile of difference spectrum was also obtained between the aerobic sperm suspension containing antimycin A and the H O oxidized one. In Hemicentrorus pulcherrimus, faint peaks of reduced cytochrome a and cytochrome c, as well as evident peaks of cytochrome b, were also found in the difference spectra between aerobic suspension of the fixed-egg-reacted spermatozoa and the H O oxidized one. In intact swimming spermatozoa of A. crassispina as well as H. pulcherrimus, no peaks of reduced cytochromes were found under aerobic condition. These results suggest that the inhibition of sperm respiration by the fixed eggs is due, at least in part, to the blockage of electron transport in a span between cytochrome b and cytochrome c.