STUDIES ON THE MECHANISM OF ACTION OF IONIZING RADIATIONS. IV. EFFECT OF X-RAY IRRADIATION ON THE RESPIRATION OF SEA URCHIN SPERM

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Abstract
The respiration of sea urchin (Arbacia punctulata) sperm increased with dilution up to a dilution of 1:200, where maximum values were found. At this dilution the average Qo2 value was 19.6 ± 3.9. When the dilution was increased to 1:1000 the respiration dropped sharply to 2.0. A dilution of 1:1600 gave no measurable respiration. The respiration of dilute suspensions of sea urchin sperm (1:200) was inhibited by x-ray irradiation. A dose of 20,000 r produced an inhibition of 66 per cent which was further increased during the second hour; 10,000 r inhibited 30 per cent; 1000 r, 22 per cent; 500 r, 14 per cent; and 100 r, 10 per cent. When sperm was irradiated with 1000 r there was no recovery of respiration five hours after irradiation. Inhibition of respiration cannot be attributed to hypothetical H2O2 formation, for sperm suspensions contain catalase. The catalase value of sperm is 33 c.mm. O2 formed by 1 mg. dry weight per hour, i.e., 3 micromoles H2O2 destroyed. On addition of succinate and of acetate to sperm irradiated by x-rays the O2 uptake inhibition increased.

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