The effects of cooling, freezing and thawing on vascular permeability and perfusion in experimental liver metastases.

The effects of cooling and freezing temperatures on vascular perfusion in solitary Walker carcinosarcomas implanted in the liver were studied in Sprague-Dawley rats. With cooling to above freezing temperatures, perfusion with Microfil decreased significantly in both the encircling tumor plexus as well as in the internal tumor circulation. Freezing and thawing produced acute, significant increases of arterial perfusion in encircling and internal tumor circulations. Tumor vascular permeability, as measured by an Evans blue extraction method, increased tremendously as a result of freezing and thawing. Significant rises in permeability were observed at five minutes to 24 hours, with peak activity at six hours. The tumor circulation appeared to respond to the insult of freezing and thawing in a manner similar to that of normal blood vessels, whereas results of previous studies have shown different reactions to chemical vasoactive agents. The acute increases of perfusion and permeability in the tumors as a result of freezing and thawing could be useful as a means of improving the concentration of antitumor agents.