We evaluated the effects of 8 mo of calorie restriction [CR: 60% of ad libi
tum (AL) food intake] on glucose uptake by 14 tissues in unanesthetized, ad
ult (12 mo) F344 x BN rats. Glucose metabolism was assessed by the 2-[H-3]d
eoxyglucose tracer technique at 1500 or 2100. Despite an similar to 60% dec
line in insulinemia with CR, plasma 2-[H-3]deoxyglucose clearance for CR wa
s greater than for AL at both times. A small, CR-related decrease in glucos
e metabolic index (R-g') occurred only at 1500 in the spleen and heart, and
this decrease was reversed at 2100. In some tissues (cerebellum, lung, kid
ney, soleus, and diaphragm), R-g' was unaffected by diet, regardless of tim
e. In the other tissues (brown fat, 3 white fat pads, epitrochlearis, plant
aris, and gastrocnemius), R-g' was higher or tended to be higher for CR vs.
AL at one or both times. These findings indicate that 8 mo of CR did not c
ause a continuous reduction in in vivo glucose uptake by any tissue studied
, and, in several insulin-sensitive tissues, glucose uptake was at times gr
eater for CR vs. AL rats.