The modification of
tumor blood flow resulting from administration of
endothelin-1 (ET-1) and
sarafotoxin S6c (SX6c) was examined in female CBH rats. Blood flow in subcutaneous HSN
tumors and normal tissues was measured by tissue uptake of 125I-labeled
iodoantipyrine ([125I])IAP). A 75% increase in
tumor blood flow was observed after 1 nM/kg ET-1, contrasting with flow in normal tissue, which was unaffected or reduced. The exception to this was the brain, in which blood flow was increased by 30%, resulting from a rise in mean arterial blood pressure (MABP) and the absence of vasoconstriction. Paradoxically, a significant drop in the
tumor vascular resistance was observed after 1 nM/kg ET-1, whereas in all other tissues the vascular resistance was significantly increased. Vascular responses to SX6c differed from those observed with ET-1. At 1 nM/kg SX6c, blood flow in the
tumor was increased to 175% of the control as a result of the increase in MABP, which was similar to ET-1. However, unlike ET-1, there was no associated vasodilatation. Vascular resistance was increased in all normal tissues with 1 nM/kg SX6c, corresponding to decreases in blood flow in the contralateral skin, skeletal muscle, and small intestine. This study therefore demonstrates that the vascular responses to ET-1 and SX6c are unique in the HSN
tumor compared to normal tissues. This atypical response of the
tumor vasculature may therefore be exploitable to improve the delivery of blood-borne anti-
cancer agents in
therapy.