Pedicled skin flaps in the pig have been used to investigate the effects of 3-h
ischemia and reperfusion on the epidermal metabolism of
glycogen and
glucose. Epidermal
glycogen content fell steadily at a rate of about 1.2 mumol of
glucose-equivalents per g wet weight per h whereas the rate of
glucose consumption declined from 1.8 mumol per g wet weight during the first hour to about 0.25 mumol per g wet weight in the third hour. During
ischemia the proportion of
glycogen synthase in the I form increased progressively from an initial value of about 8% to about 70%, but the proportion of
phosphorylase in the a form decreased only in the third hour of
ischemia. The concentration of
ATP decreased and
ADP and
AMP increased but the total pool of epidermal
adenine nucleotides was not depleted. On reperfusion, these changes were reversed and normal epidermal concentrations of
glucose and
adenine nucleotides were restored within 30 min and remained stable thereafter. The resynthesis of
glycogen proceeded at a steady rate of about 1 mumol per h per g wet weight and the phosphorylation state of both
glycogen synthase and
phosphorylase approached normal values after 3 h. It is concluded that epidermal glycogenolysis in
ischemia is, at least in part, a consequence of activation of
phosphorylase b by
AMP, and that
glycogen resynthesis on reperfusion is promoted by the ischemic activation of
glycogen synthase.