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The radioprotectant WR 2721 administered intraperitoneally to rats at 30--40 min before exposure to 1000 rad of 60Co caused a reduction in spleen lysosomal enzyme activity and fluctuations in cyclic nucleotide levels. Liver and spleen cAMP levels from drug-treated animals were higher at 3--6 hr postirradiation whereas spleen cGMP levels were lower at 1--4 hr postirradiation than irradiated controls not given the radioprotectant. At 3 days after radiation exposure, spleen cyclic nucleotide levels and lysosomal enzyme activities in rats given WR 2721 were closer to the level of nonirradiated control rats than of irradiated rats receiving saline.

A clinically asymptomatic individual had an abnormal electrophoretic pattern for lactate dehydrogenase, seven isoenzyme bands being present. This atypical pattern was a result of an interaction of lactate dehydrogenase with immunoglobulin A and beta-lipoprotein. Lactate dehydrogenase enzymes LD2 and LD3 were the isoenzymes responsible for the formation of the complexes.

Sterols of a nystatin resistant mutant of the wild type parent of Saccharomyces cerevisiae were separated by a newly developed procedure involving high-pressure liquid chromatography and were identified. The mutant contained larger amounts of squalene and lanosterol (I) than the wild type, as well as 4,14-dimethylcholesta-8,24-dien-3beta-ol (II), 4,14-dimethylergosta-8,24(28)-dien-3beta-ol (III), and 14-methylergosta-8,24(28)-dien-3beta-ol (IV), which were not hitherto found in yeast. These results indicated a block in removal of the methyl group at C-14 of lanosterol. An ergosterol requiring derivative of the mutant which carried in addition a mutation in heme biosynthesis had the same sterols as the parent, but at one-third the concentration. The low level of sterols may be due to a requirement for a heme or cytochrome in oxygenation reactions between lanosterol and ergosterol.

Within 1 hr after ip injection of the radioprotectant WR 2721 into rats, splenic cGMP levels dropped and remained suppressed for 6 hr before returning to normal. However, if rats were exposed to ionizing radiation 30-40 min after WR 2721 treatment, they had higher cGMP levels at 3 hr postirradiation than the nonirradiated, drug-treated controls, but the cGMP content was still found to be lower than that of the irradiated nondrug-treated controls. Radiation exposure of animals pretreated with WR 2721 also resulted in higher liver and spleen levels of cAMP and additional elevations in spleen prostaglandin content, compared with irradiated controls at 3-6 hr after radiation treatment. The secondary fluctuations of lysosomal enzyme activities, prostaglandin content, and cyclic nucleotide levels were also altered in irradiated rats pretreated with WR 2721 when compared with irradiated controls. Liver and spleen lysosomal beta-glucuronidase activities, spleen cAMP and cGMP levels, and spleen prostaglandin concentrations were closer to physiological levels at 3 days postirradiation in rats given WR 2721 before the radiation treatment.

Whole-body irradiation of rats results in the release of hydrolases from lysosomes, an increase in lysosomal enzyme activities, and changes in the prostaglandin levels in spleen and liver tissues. A transient increase in the concentration of prostaglandins E and F and leakage of lysosomal hydrolases occurred in both spleen and liver tissues 3-6 hours after the animals were irradiated. Maximal values for hydrolase activities, prostaglandin E and F content, and release of lysosomal enzymes were found 4 days postirradiation in rat spleens whereas in the liver only slight increases were observed at this time period for prostaglandin F levels. On day 7 there was a final rise in the spleen's prostaglandin E and F concentrations and leakage of hydrolases from the lysosomes before returning to near normal values on day 11. The prostaglandin F concentration in liver was also slightly elevated on the 7th day after irradiation and then decreased to control levels.