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Adipocytes were prepared from the epididymal fat pads of rats trained by swimming (T) and from control rats matching the T rats with respect to free-feeding and age (FC), body weight and age (WC), or mean fat cell size and age (CC). The number of epididymal fat cells was the same in all groups, whereas the mean adipocyte volumes (in pl) differed (P less than 0.01): 153 (T and CC), 266 (WC), and 540 (FC). The initial influx rate of 3-O-14Cmethylglucose (60 mumol/liter) in maximally insulin-stimulated adipocytes was more than twofold higher in T rats than in any control group (P less than 0.01). In the control groups, influx was positively correlated to cell size. Also the maximally insulin-stimulated incorporation of 14C from U-14Cglucose into lipids was significantly higher in T rats than in the control groups. The saturable binding of mono125I-TyrA14insulin was about 18% higher in T rats than in WC rats in the insulin concentration range from 30 to 20 X 10(4) pmol/liter. In conclusion, physical training markedly increases 3-O-methylglucose transport in fat cells, an effect that cannot be elicited by reduction in body weight or fat cell size.
Vinten et al. (Tue,) studied this question.