ABSTRACT
In spermatozoa of all examined sea urchins, the respiration was inhibited and their motility was lowered by the glutaraldehyde-fixed eggs. The respiration of the fixed-egg-reacted spermatozoa was stimulated by 2, 4 dinitrophenol in Clypeaster japonicus, Hemicentrotus pulcherrimus and pseudocentrotus depressus but was not in Anthocidaris crassispina and Toxopneustes pileolus. Ratio of ADP to ATP was markedly lower in the reacted spermatozoa of the former species than in those of Anthocidaris. The low respiratory rate in the former species probably results from ADP control but does not in the latter species. Tetramethyl-p-phenylenediamine enhanced the respiratory rate in the reacted spermatozoa of the latter species to almost the same rate as in the intact spermatozoa, but elevated slightly in the former species. The inhibition of electron transport in mitochondrial respiratory chain is probably predominant in the latter species. In the former species, the slight inhibition of electron transport does not seem to result in a failure of ADP phosphorylation, and hence the stop of movement probably causes a shortage of ADP. Carnitine, which made the reacted spermatozoa of all species motile, enhanced the respiratory rate only in those of the former species.
ABSTRACT
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 H2 O2 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 H2 O2 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 H2 O2 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.
ABSTRACT
The respiration of spermatozoa of the sea urchin, Hemicentrotus pulcherrimus, was found to be sensitive to rotenone, antimycin A, and cyanide. This suggests that sperm respiration results from electron transport which spans the whole mitochondrial respiratory chain. The sperm respiration was inhibited by oligomycin and this inhibition was released by 2, 4-dinitrophenol (DNP). DNP did not stimulate the respiration of spermatozoa in a diluted suspension (2 × 108 /ml), where they were swimming vigorously. The ADP level of spermatozoa in the diluted suspension was markedly higher than that in dry sperm. The spermatozoa, which had reacted with unfertilized eggs fixed with glutaraldehyde, were immotile with a quite low respiratory rate. The respiratory rate of the immotile spermatozoa was enhanced by DNP. In the immotile spermatozoa, ADP level was markedly low and the ATP level was as high as that in dry sperm. From these findings, it is concluded that in the swimming spermatozoa respiration coupled with oxidative phosphorylation occurs at the maximum rate. State 3 respiration probably occurs in the swimming spermatozoa. The low respiratory rate of the immotile spermatozoa is assumed to be due to a shortage of ADP and is practically regarded as state 4 respiration.
