STROMA-FREE HUMAN HEMOGLOBIN A DECREASES R3230AC RAT MAMMARY ADENOCARCINOMA BLOOD-FLOW AND OXYGEN PARTIAL-PRESSURE

We examined the effect of a nitric oxide (NO) quencher, stroma-free hu man hemoglobin A (HbA(0); 0.01, 0.05, 0.1, 0.2 g/kg), on the blood flo w measured using the Doppler flow technique, tumor oxygen pressure (pO (2)) and the diameter of the arterioles using R3230Ac mammary adenocar cinoma as the tumor model. In female Fischer 344 rats with 1-cm-diamet er tumors implanted in the lateral aspect of the left quadriceps, intr avenous infusion of 0.1 and 0.2 g/kg HbA(0) decreased both central tum or and peripheral tumor blood flow by 20-30% (P < 0.05). Tumor pO(2) d ecreased 28% with 0.2 g/kg HbA(0), from 15 mm Hg (baseline) to 11 mm H g at 10 min (P = 0.02). Although 0.2 g/kg HbA(0) increased blood flow 55% in the left quadriceps muscle proximal to the implanted tumor (P < 0.05), HbA(0) had little effect on blood flow in right quadriceps mus cle with no tumor implanted, and increased right quadriceps pO(2), fro m 21 mm Hg (baseline) to 23 mm Hg at 10 min (P = 0.03). HbA(0) increas ed mean arterial pressure 5-10% in a manner that was dependent on dose while heart rate concurrently decreased 9-19%. The diameter of the ar terioles supplying the tumor was rapidly reduced 10% by 0.2 g/kg HbA(0 ) (P = 0.037) and remained stable through 60 min of observation (P = 0 .005). HbA(0) selectively reduces tumor blood flow and tumor pO(2) thr ough vasoconstriction of the arterioles supplying the tumor. Vascular NO quenching provides an alternative to NO synthase inhibition as a me ans to achieve the goal of selective tumor hypoxia. (C) 1997 by Radiat ion Research Society.