Influence of vasoactive drugs on local tumor blood flow.

The influence of vasoactive drugs, including noradrenaline, isoprenaline and papaverine, on the local blood flow of a transplantable rat sarcoma and of normal subcutaneous tissue of the rat was studied by local [133 xenon] clearance technique. The microvascular bed of the tumour was studied by transmission electron microscopy (TEM). Vessels with one layer of contractile cells were found in the tumour vascular bed by TEM. A significant reduction of both tumour and normal subcutaneous tissue blood flow was found after administration of noradrenaline added to the injected xenon solution. In a dose-response experiment the tumour and subcutaneous vascular beds seemed to be equally sensitive to noradrenaline. Isoprenaline did not influence the blood flow in either subcutaneous tissue or tumour, while papaverine increased subcutaneous tissue blood flow significantly but did not influence tumour blood flow. The results of the present blood flow studies might suggest that the tumour vascular bed is normally in a state close to maximal dilatation.