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Vascular reactivity to norepinephrine of 7,12-dimethylbenz(a)anthracene-induced rat mammary tumors and normal tissue as studied in vitro.

Vascular reactivity to norepinephrine has been studied in dimethyl-benz(a)anthracene-induced rat mammary neoplasia and compared with that of skeletal muscle, salivary gland, kidney, and uterus by means of an artificial perfusion technique. Perfusion of tissues and organs was measured with the microsphere tracer technique during smooth muscle relaxation and infusion of norepinephrine at two different dose levels. This procedure makes possible a dose-response analysis of several tissues under controlled conditions without confounding endogenous vasoregulation. The tumor vascular bed has a low perfusion capacity during smooth muscle relaxation and responds rapidly with an increased resistance to norepinephrine infusion. The results indicate a hypersensitivity, although the relative maximal constrictor response is equal to or less than that of other vascular beds studied.