Three phases of
starvation have been described from changes in
protein and
lipid utilization in birds and mammals. In the present study, tissue
glucose utilization was measured in vivo during these three phases, using a 2-deoxy-[1-3H]
glucose technique in the anesthetized rat. According to this technique, the term
glucose utilization therefore refers to transport and phosphorylation of
glucose in tissues, ie, whatever is the fate of
glucose. Whole-body
glucose turnover rate, which was determined by a continuous infusion of [3-3H]
glucose, decreased by 40% during the first two days of
starvation (phase 1); it did not change thereafter, neither in the
protein-sparing phase 2 nor in phase 3, which is marked by an increase in net
protein breakdown. Two days of
starvation caused a marked decrease in the
glucose utilization in skeletal muscles; this decrease was higher in oxidative muscles (65% in diaphragm, 66% in soleus) than in glycolytic muscles (31% in extensor digitorum longus, 34% in epitrochlearis).
Glucose utilization also decreased in heart atria (75%), heart ventricles (93%), and white adipose tissue (54%); by contrast, there was a two-fold increase in
glucose utilization in brown adipose tissue and no change in brain and skin. No variations were observed in
glucose utilization in any of the tissues from phase 1 to phase 2. However, phase 3 was marked by a decrease in
glucose utilization in extensor digitorum longus (45%), brown adipose tissue (76%), brain (29%), and skin (40%), whereas there was a 2.3- and 3.4-fold increase in
glucose utilization in diaphragm and heart ventricles, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)