The adult trematode, Fasciola hepatica and Eurytrema pancreaticum, employed in this experiment were obtained from the cattle slaughtered at the local abbatoir. The worms were selected and washed several times in normal sterilized saline solution. Each ten of intact F. hepatica and about thirty to fifty of E. pancreaticum were incubated in 50 cc volume of special incubation flasks with incubation medium consisting of 50 cc of Krebs-Ringer phosohate buffer (pH 7.4). The incubation medium was added C¹⁴-lactate and non-radioactive carrier Na-lactate so as to contain lactate concentration of 32 mg per cent. The worms were allowed to incubate for 3 hours in the Dubnoff metabolic shaking incubator at 38℃.

After incubation period, respiratory CO₂ samples from central wall of incubation flask were analysed for total CO₂ production rate and their specific activity of respiratory CO₂. The lactate uptake rate was determined by analyzing the the difference between lactate concentration in a medium before and after the incubation period, and the pyruvate appearance rate was dertermined by analyzing the pyruvate concentration in a medium after incubation. The glycogen samples isolated from worms were analyzed for the tissue concentration and their radioactivities in order to determine the turnover rate of glycogen pool. Radioactivities of these serise of experiment were counted by an endwindow Geiger-Muller counter as an infinitely thin samples.

The quantative analysis of C¹⁴-lactate utilized by F. hepatica and E. pancreaticum were summerized and compared as following.

In F. hepatica the lactate uptake rate was a mean value of 1.04±0.15 micromole/hr/g of wet wt. and pyruvate apperance rate was a mean value of 0.132±0.005 µM/hr/g of wet wt. The total CO₂ production rate by the flukes averaged 13.82±0.75 µM/hr/g of wet wt. The relative specific activities of respiratory CO₂ showed a mean value of 9.93±0.62 per cent. The rate of CO₂ production derived from medium C¹⁴-lactate was a mean of 1.38±0.13 µM/hr/g of wet wt. Therefore the averge value of 55.27±5.78 per cent (R.L.D. CO₂) and 15.35±1.90 per cent (R.L.D. pyr) of lactate was oxidized into respiratory CO₂ and pyruvate respectively.

On the other hand, in E. pancreaticum the lactate uptake rate was a mean value of 0.61±0.18 micromole/hr/g of wet wt, and pyruvate appearance rate was a mean of 0.023±0.001 micromole/hr/g of wet wt. The total CO₂ production rate by the E. pancreaticum averaged 4.29±0.85 micromole/hr/g of wet wt. The relative specific activity of respiratory CO₂ (R.S.Aco₂) showed a mean value of 9.20±0.34 per cent. Thus, a mean value of 9.20 per cent of total CO₂ production rates was originated from C14-lactate in a medium, therefore the rate of CO₂ production derived from medium C¹⁴-lactate was a mean value of 0.40±0.10 micromole/hr/g of wet wt. The average value of 23.93±7.11 per cent(R.L.D. CO₂) and 3.86±0.45 per cent(R.L.D. pyr) of lactate was oxidized into respiratory CO₂ and pyruvate respectively.

The tissue concentration of glycogen in F. hepatica was a mean of 2.63 per cent/g of wet wt, while in E. pancreaticum was a mean of 4.06 per cent/g of wet wt. The turnover rate of glycogen pool in F. hepatica yielded a value of 0.073±0.008 micromole/hr/g of wet wt whereas in E. pancreaticum yielded only a mean of 0.006±0.002 mg/hr/g of wet wt. Therefore, the half time of glycogen turnover, which is the time interval required to replace the half of glycogen pool with medium C¹⁴-lactate, gave value of a mean of 10.73±0.76 days in F. hepatica. However, incorporation of C¹⁴-lactate into glycogen was negligible in the E. pancreaticum.

Theses data impressed that the carbohydrate such as lactate may play a role of major part of their oxidative metabolism in F. hepatica, whereas minor part of lactate participates in the oxidative metabolism in E. pancreaticum.