15Nを用いたたん白欠乏ラットの尿素利用について

田中 紀子

doi:10.4327/jsnfs1949.35.175

Three experiments were performed to investigate the mechanism of urea utilization and the nutritional roles of intestinal flora on the utilization of urea by rats fed with a protein deficient diet. The results obtained were as follows; 1) Ammonia content in the small intestine in LPD (Low Protein Diet) group fed with a low protein diet for 2 or 5 weeks was about three of five times higher than that of control group fed with SPD (Standard Protein Diet) after administration of urea (0.2gN/100g B.W.). The increased ammonia in the small intestine by LPD group is presumably due to the increased urease activity in the intestine, because it is generally accepted that the intestinal urease is entirely microbial in origin. 2) The ¹⁵N incorporation into plasma protein of LPD group was significantly higher than that of the control group two hours after the administration of ¹⁵N-urea (10mg/100g B.W.) and a higher level of ¹⁵N concentration in plasma protein in LPD group was maintained thereafter. The ¹⁵N incorporation into the amino acids (Lys, EAA, NEAA) of plasma protein was higher in LPD group than in control group. EAA means the mixture of essential amino acids and NEAA means that of nonessential amino acids. The differences in incorporation rate of ¹⁵N between LPD and SPD group were significant (p<0.05) in case of EAA and NEAA. 3) The ¹⁵N incorporation into Lys, EAA and NEAA in portal plasma seemed to be higher in LPD group than in control group one hour after the administration of ¹⁵N-urea (10mg/100g B.W.). However, the ¹⁵N incorporation into each free amino acids was suppressed considerably by the administration of antibiotic mixture. It follows that amino acids may be synthesized from urea in the intestine by intestinal-bacterial action and absorbed from portal vein. Those amino acids may be incorporated into plasma protein as indicated in 2). From these results, it may be concluded that the ammonia nitrogen converted from urea by the action of intestinal-bacterial urease in the intestine is utilized for the synthesis of essential and nonessential amino acids in protein deficient rats and transfered to the liver through portal vein and utilized for protein synthesis. It is suggested that protein deficiency may change the population of intestinal bacteria so as to increase the urease activity. This change may be one of the adaptive responses to low protein diet to conserve nitrogen.

<SUP>15</SUP>Nを用いたたん白欠乏ラットの尿素利用について

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