Glucose metabolism in epididymal adipocytes of rats taking voluntary exercise
1989 Volume 56 Issue 5 Pages 440-448
Details
1989 Volume 56 Issue 5 Pages 440-448
The purpose of this study was to investigate the effects of voluntary running on the glucose metabolism in isolated adipocytes. Male rats of the Wistar strain, 5 weeks old were separately fed on usual rat food in cages equipped with a rotating wheel. The control rats were kept in small cages without wheels for 8 weeks in both experiments. The exercised rats ran approximately 2 km/day during this period.
There were significant differences in the body weights and the weights of the epididymal fat pads between the exercised rats (373.5±10.3g SEM and 4.2±0.3g SEM) and the sedentary rats (437.8±17.6g SEM and 7.9±0.3g SEM) (p<0.05 in both cases).
The rate of [U-14C]-glucose oxidation measured by 14CO2 production in adipocyte cultures showed a tendency toward greater stimulation in the exercised rats than in the sedentary ones, both when no insulin was added to the incubating medium (0.42±0.18% SEM vs. 0.11±0.02% SEM, p<0.10) and when insulin was added (0.81±0.36% SEM vs. 0.15±0.02% SEM, p<0.05). Hexokinase activity in the cells also seemed to be more stimulated in the exercised rats than in the sedentary ones.
Conversion of [U-14C]-glucose to triglyceride was not affected significantly in the above experiment either with respect of the exercised rats vs. sedentary rats or with respect of the presence of insulin in the incubating medium.
The number of insulin receptors and affinity constants of adipocytes in both groups was measured by Scatchard analysis. There were three times more binding sites in the exercised rats than in the sedentary ones (93.4×108vs. 29.7×108 sites/105 cells). However there was no difference in affinity constants of the receptors in both cases, Ke (2.8×108vs. 2.7×108 M-1) and Kf (0.9×108vs. 1.0×108 M-1) which were calculated by the "negative cooperative theory".
These results indicated the stimulative effects of voluntary running on insulin sensitivity, the rate of glucose transport and glucose oxidation in rat adipocytes.
