Effect of reduced perfusion pressure and acetylcholine on local blood flow in tumors in the rat kidney.

The local blood flow (LBF) in a sarcoma and a hepatoma implanted into the rat kidney was examined during renal vasodilation, with and without increased total renal blood flow (RBF). Both tumor types had a control LBF of about 0.7 ml/min per g, i.e. 35 per cent or less as compared with the renal LBF, as simultaneously determined by the H2 gas clearance technique. The RBF averaged 4.6 ml/min per g as recorded electromagnetically. During about 20 mmHg reduction of renal arterial pressure the tumor LBF was maintained relative to the renal LBF, whether the RBF was autoregulated or not. Provided neoplastic vessels account for most of the vascular resistance to tumor blood flow, they must therefore possess autoregulatory ability. The tumor LBF was maintained when the RBF was maximally increased by continuous renal arterial infusion of acetylcholine. This may suggest that a neoplastic vessel vasodilatory response to acetylcholine prevented reduction of the tumor flow.