Experimental study on mechanism of absorption of cryonecrotized tumor antigens

On Day 7 of subcutaneous MRMT-1 tumor inoculation in the thigh of Sprague-Dawley rats, the tumor was treated cryosurgically by contact method. Postoperative changes in local blood circulation were observed by colloidal carbon perfusion and hydrogen-clearance methods, and the pathway and time course of tumor antigen absorption were observed by measuring uptake in serum and lymph nodes of [3H]thymidine injected intratumorally. Results were: At 0.5 to 1 hr after cryosurgery, vascular stasis, dilatation, and tortuosity were observed. There was no inflow of carbon and almost no uptake of [3H]thymidine. At 6 hr, vascular stasis and sludging become more marked. There was no inflow of carbon, while uptake of [3H]thymidine markedly increased. At 24 hr, some carbon inflow in fin vessels and partial recovery of blood circulation in the peritumoral region were observed. Rate of [3H]thymidine uptake was further increased. At 72 hr, carbon inflow and blood circulation increased further, while the cryonecrotized tumor showed hyaline degeneration. At 168 hr, increase of newly formed vessels and recovery of blood circulation were remarkable, but uptake of [3H]thymidine was decreased in parallel with increased demarcation of the cryonecrotized tumor. From these results, it was suggested that the absorption of cryonecrotized tumor antigens started through lymphatic channels in the early period and then took place also through newly formed capillaries surrounding the tumor at 24 hr after cryosurgery and continued until 72 hr after cryosurgery.