흰쥐 간장절편에 있어서 C14-pyruvate의 대사과정에 관한 실험

Abstract

Liver slices of rats were incubated with C'<pyruvate incubation mixtures of different concentrations. Incubation was continued up to 5 hours. During the incubation period, liver slices were exposed to fresh media by hourly replacement of fresh incubation mixture. Hourly samples, obtained through the replacement of medium, were analyzed for pyruvate, lactate, CO2 and specific activity (SA) of respiratory CO2• Thirty two Sprague-Dawley rats were divided into 4 groups of 8 each. Different concentrations of pyruvate incubation medium were used for each group. Group 1 was incubated with pyruvate solution of 10 mg/dl, group 2 with 20mg/dl, group 3 with 30mg/dl and group 4 with 40mg/dl pyruvate solution. The following results were obtained. 1) Pyruvate disappearance rate, lactate accumulation rate and total CO2 production rate decreased during the initial 3 hours of incubation period and remained approximately constant. Relative specific activity (R SA) and CO2 produced from the medium C'<pyruvate increased exponentially during the early 3 hours and reached to plateau values. These steady or plateau values were used as the reference to compare the metabolic rates between each group. 2) Pyruvate disappearance rates were 4. 2pM/hr/gm of tissue in group 1, 7. 1 for group 2, 8. 8 for group 3 and 10 for group 4. Thus pyruvate disappearance rates increased below 30mg/dl of pyruvate concentration as the concentration of pyruvate in the incubation medium increased and remained approximately constant at concentration of greater than 30mg/dl. 3) Lactate accumulation rates for each group were 3. 3pM/hr/gm of tissue, 3. 5, 3. 8 and 4. 1 respectively, There were little changes in lactate accumulation rates despite the change in concentration of medium pyruvate. 4) Total CO2 production rates for each group were 24. 4pM/hr/gm of tissue, 23.0, 26. 0 and 27. 3, respectively. These rates also showed little changes as shown in the lactate accumulation rate. RSA and CO2 production rates derived from medium C'<pyruvate increased at concentration of medium pyruvate below than 30mg/dl and remained approximately constant at the concentration of C'<pyruvate greater than 30mg/dl. The percentage of CO2 derived from medium C'<pyruvate to total CO2 production or RSA for each group were 7. 1, 9. 4, 14.2 and 14. 7%, respectively, while CO2 production rates derived from medium C'<pyruvate were O. 6pM/hr/gm of tissue, 0.7, 1.2 and 1. 3, respectively. 5) Fractions of pyruvate disappeared into respiratory CO2 to total pyruvate disappearance, which is refered to RPD, ,2, were 13.8, 10.1, 14.0 and 13.4%, respectively, for each group and RPD lactate for each group were 78.6, 49.3, 43.2 and 41. 0%. Therefore, average of 92.4% of total pyruvate disappeared from the medium in the group 1, 59.4% in the group 2, 57.2% in group 3 and 54.4% in group 4 were found to be accounted for by the conversion of respiratory CO2 and lactate accumulation.