Influences of Aging on the Changes in Nucleic Acid Metabolism Induced by Surgical Stress
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概要
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In view of the importance of obtaining informations concerning the metabolic response to surgical stress in the early stage at individual organs. The authors have studied the influences of aging on the metabolism of nucleic acids, situating at the crossroad of the energy metabolism and protein biosynthesis.Metabolic response of nucleic acids under surgical stress was studies in male mice of DDY-strain, with the superficial burn on the hind limbs and tail.1. DNA and RNA content in the liver and skeletal muscles were estimated quantitatively by the Schmidt-Thannhauser procedure. In the skeletal muscles of mice (6 weeks old, 20g of body weight), total nitrogen, total creatinine and RNA per gram of wet tissue, were considerably reduced during the period from 8 to 15 hours after the burn. In the liver, on the other hand, the quantity of total nitrogen per gram of wet tissue was not markedly changed after the burn, and the quantity of RNA was increased (p<0.1), associated with the definite increase of tissue transaminase activity (p<0.01).2. The control (pre-burn) value of RNA per gram of wet liver tissue was reduced in aged mice group of 10 months of age than in younger mice group of 6 weeks of age (p<0.01). Although the quantity of RNA was increased even in aged mice during the period of 16 hours after the burn, each RNA value was lower at any period after the burn in aged mice compared with the correspondine values in younger mice.3. 32P incorporation in-vivo was estimated in the liver 15 hours after the burn.50μc of 32P per 20g of body weight was injected intraperitoneally 3 hours after the burn, and the specific activity in liver of the burned mice was compared with the specific activity in the control group. Definite increase of 32P incorporation of ribonucleic acids (both s-RNA and r-RNA) was revealed even at 11 hours after the burn in the liver of younger mice (6 weeks old), but the increase of 32P incorporation was slower up to 15 hours after the burn in the liver of aged mice (10 months old).The quantity of upper ribonucleic acids per gram of wet tissue seemed to be decreased in the liver of patients above the sixth decades who underwent upper abdominal operation.Although further studies would be necessary to get more precise information, the increased turnover of nucleic acids metabolism in response to surgical stress appears to be more pronounced in young individuals than in the aged.
- 社団法人 日本老年医学会の論文