Reduced oxygenation in a rat mammary carcinoma post-radiation and reoxygenation with a perflubron emulsion/carbogen breathing.

Oxygen profiles of the rat mammary 13672 carcinoma were determined using a pO2 histograph prior to treatment and 24 hrs. and 48 hrs. after 2 or 5 fractions of 3 gray given once daily. The tumors were much more hypoxic at 24 hrs. post radiation therapy than prior to therapy. There was little increase in the oxygenation of the tumors at 48 hrs. post therapy compared with 24 hrs. post therapy indicating that reoxygenation was occurring very slowly in this tumor. Carbogen breathing improved the oxygenation of the tumors under each of the conditions studied. Administration of a perflubron emulsion (8 ml/kg) produced little or no change in the oxygenation of the tumors under normal air breathing conditions. However, with the addition of carbogen breathing to administration of the perflubron emulsion there was an increase in the mean/median pO2's of the tumors to levels equal to or greater than carbogen breathing alone. Perhaps most significantly administration of the perflubron emulsion with carbogen breathing increased the oxygenation of the most hypoxic regions of the tumors but carbogen breathing alone did not.