Tl-201 and Tc-99(m) human serum albumin for assessment of the effect of hypertensive treatment with angiotensin II infusion on tumour circulation

The biodistribution of Tl-201 and of Tc-99(m)-human serum albumin (Tc-99(m)-HSA) was observed in tumour-bearing mice to investigate if tissue blood circulation could be evaluated in groups of mice infused with angiotensin II at a rate of 0.5 mu g kg(-1) min(-1) (L) or 1 mu g kg(-1) min(-1) (H). Ten minutes after tracer injection, tumour uptake of Tl-201 in the angiotensin II infused group showed a 2.20- and a 3.18-fold increase in the L and H groups, respectively, when compared to a group of mice infused with saline (P = 0.0478 and 0.0029, respectively). The effect of angiotensin II infusion on Tl-201 uptake was minimal in normal organs. Decreased normal organ uptake of simultaneously injected Tc-99(m)-HSA in the L and H groups indicated the contraction of normal organ vessels, while increased tumour uptake of the tracer indicated mechanical dilatation of tumour vessels. We conclude that the effect of angiotensin II or other vasoactive agents can be non-invasively assessed by Tl-201 and Tc-99(m)-HSA scintigraphy.