(A) Perfusion protocol for renal survival after vitrification and rewarming. M, molarity; A-V (M), arteriovenous difference in molarity; T, temperature in degrees Celsius. The protocol, as usual,6,39 employs an initial 5 M plateau, a second plateau at 8.4 M to allow cooling to −22°C without freezing, and a final plateau during M22 perfusion. In the experiment shown, the perfusion was interrupted at the point shown to enable the kidney to be vitrified, rewarmed and reperfused with 8.4 M cryoprotectant at −3°C. (B) Thermal history of the transplanted kidney based on invasive temperature measurements in a model rabbit kidney cooled and rewarmed by a procedure identical to that used for the vitrified-transplanted rabbit kidney. Line 1: inner medullary temperature, as documented by a thermocouple located 1.2 cm below the renal surface; line 2: outer medullary temperature, measured 7 mm below the renal surface; line 3: cortical temperature 2 mm below the renal surface; line 4: environmental temperature of the test kidney; line 5: environmental temperature of the kidney that was transplanted after previous vitrification. TM,IM, estimated melting point of inner medullary tissue (upper horizontal line); TG, estimated glass transition temperature of inner medullary tissue (lower horizontal line).