LOCALIZED HYPOTHERMIA - IMPACT ON OXYGENATION, MICROREGIONAL PERFUSION, METABOLIC AND BIOENERGETIC STATUS OF SUBCUTANEOUS RAT-TUMORS

The effect of localized hypothermia on microcirculatory and metabolic parameters in s.c. DS sarcomas on the hind foot dorsum of Sprague-Dawl ey rats was investigated. Tumours were cooled by superfusion of the tu mour surface with cooled saline solution to 25 degrees C or 15 degrees C. Control tumours remained at 35 degrees C. These temperatures were maintained for 30 min. In tumour oxygenation measurements, hypothermia at 25 degrees C and 15 degrees C caused progressive decreases in the size of the fraction of pO(2) measurements between 0 and 2.5 mmHg toge ther with a reduction in pO(2) variability. No significant changes in median or mean pO(2) or in the fraction of pO(2) measurements between 0 and 5 mmHg, and 0 and 10 mmHg were observed. Using laser Doppler flo wmetry, red blood cell flux was found to decrease significantly upon 2 5 degrees C or 15 degrees C hypothermia treatment to 67% and 37% of st arting values respectively, whereas no significant changes were seen i n control tumours over the whole observation period. Viscosity was mea sured in blood and plasma samples over a range of temperatures and was found to increase with decreasing temperature. Assessment of tumour g lucose levels showed an increased concentration of glucose following 1 5 degrees C hypothermia, an observation consistent with a 'slowing dow n' of glycolysis. No changes in lactate or adenylate phosphate levels were observed. As a way of improving tumour oxygenation, localized hyp othermia may therefore be a useful means of radiosensitization.