The effects of pentoxifylline on the relative perfusion of tumours growing in three sites in the mouse.

The haemorheological agent pentoxifylline (PTX) has been shown to improve the relative perfusion and oxygenation of subcutaneous tumours in the mouse. In order to establish whether this effect is dependent on the site of tumour growth, we have looked at changes in the distribution of the cardiac output (COD) to the murine NT carcinoma grown either intradermally (i.d.), intramuscularly (i.m.), on the wall of the caecum, or in all three sites, following i.p. administration of 50 mg kg-1 PTX. In animals bearing a single tumour, PTX treatment significantly increases the COD to tumours located in the caecum, but has no significant effect on the COD to those located in the i.d. or i.m. sites. If all three tumours are present in a single animal, the COD to all three tumours is significantly enhanced by PTX. This appears to reflect the presence of the caecum tumour and does not appear to relate to changes in tumour size or to the haematocrit (HCT) of the blood. We propose that this site dependency implies that a significant increase in blood viscosity only occurs in animals with tumours located in specific sites. Therefore, the potential radiosensitising capability of PTX is highly dependent on tumour location.