(CO2)-C-13 peak value of L-[1-C-13]phenylalanine breath test reflects hepatopathy

Background. Using a rat model of hepatectomy, we investigated whether the s everity of hepatopathy could be quantitatively measured from changes in exp iratory (CO2)-C-13 levels after intravenous administration of L-[1-C-13]met hionine or L-[1-C-13]phenylalanine. Materials and Methods. Under nembutal anesthesia, 30 mg/kg L-[1-C-13]phenyl alanine or 40 mg/kg L-[1-C-13]methionine was administered to rats through t he femoral vein, and expiratory (CO2)-C-13 levels were measured for 15 min. A 30, 70, or 90% hepatectomy was performed. In the control group, simple l aparotomy was performed. Breath test was conducted 20 min after laparotomy. We examined the correlation of the total (CO2)-C-13 output over 15 min or peak (CO2)-C-13 level with liver weight/body weight (%). Results. In breath test graphs, L-[1-C-13]methionine did not show any peak level during measurement. L-[1-C-13]phenylalanine showed a specific peak. l evel 6 +/- 1 min after administration. The correlation coefficient between total (CO2)-C-13 output over 15 min after. L-[1-C-13]methionine administrat ion and liver weight/body weight was 0.922 (P < 0.001). The correlation coe fficient between total (CO2)-C-13 output over 15 min after L-[1-C-13]phenyl alanine administration and liver weight/body weight was 0.883 (P < 0.001). The correlation coefficient between peak L-[1-C-13]phenylalanine level and liver weight/body weight was highest, 0.927 (P < 0.001). Conclusion. In a breath test with intravenously administered L-[1-C-13]meth ionine or L-[1-C-13]phenylalanine, hepatopathy could be quantitatively eval uated by measuring expiratopy (CO2)-C-13 levels over 15 min. After admin is tration of L-[1-C-13]phenylalanine, hepatopathy could be quantitatively eva luated in a short period by measuring the peak expiratory (CO2)-C-13 level. (C) 1999 Academic Press.