Recovery of oxidative phosphorylation in rat liver mitochondria after whole body irradiation.

There have been many conflicting reports on the effects of x-rays in vitro and in vivo on respiration and phosphorylation in various animal tissues. Kusnets (1) reported a decrease in spleen respiration within 30 minutes after rats had received whole body irradiation of 800 r, and Sullivan and Dubois (2) recorded a similar decrease with 400 r which reached a maximum after 48 hours. Barron (3) found reduced respiration with 200 r; van Bekkum (4) reported a decrease after irradiation, with as small a dose as 100 r. Conversely, mouse spleen seemed unaffected by 640 r (5). Snezhko (6) found an increase in O2 tension in rabbit brain with doses of 900 r, whereas Florsheim, Doernback, and Morton (7) reported no significant changes in mouse brain respiration with doses as high as 19,000 r. Barron (3) saw little effect on rat liver respiration with 800 r, whereas Kusnets (1) found considerable reduction in O2 uptake. Hanel, Hjort, and Purser (8) reported an increased respiration in liver from rats exposed to 450 r of whole body irradiation. Muscle and kidney tissue showed almost no respiratory effects with doses as high as 800 r (1). Potter and Bethel1 (9) showed a reduction in oxidative phosphorylation in spleen mitochondria subjected to 800 r in vivo. Dubois and Paterson (10) thought that this reduction was due to increased ATPase activity, but this was disputed by Ashwell and Hickman (5) who used fluoride as an ATPase inhibitor. Goldfeder (11) demonstrated a decrease in oxidative phosphorylation in mouse liver mitochondria with 700 r of whole body irradiation, but van Bekkum (12) found no reduction in P :0 ratios in liver mitochondria from rats exposed to considerably over 700 r, and Toropova (13) reported no decrease in ATP synthesis in liver homogenates from rats exposed to 650 r. Because of the conflicting evidence and the variety of preparations and dosages reported to date it was thought advisable to reinvestigate the problem using carefully reproducible doses, various substrates, and mitochondria prepared under rigidly controlled conditions. Oxidative phosphorylation was measured at intervals up to 72 hours after whole body irradiation.