A rapid increase of the total number of binding sites for T3 appeared within 30 min of ischemia and reached over 40% by 3 h. During the same 3-h period, the relative binding affinity was reduced by 25%. Upon recirculation after 30 min or 3 h of ischemia, a rapid reversal of measured T3 binding sites occurred, which progressed to 20-30% below the control value by the recirculation period of 3 h.