The response of tumor vessels to vasoactive substances could provide useful information on experimental tumor biology. We have studied the effects of noradrenaline (20 μg/kg i.v.) on cardiac output (%CO) distribution in C57BL/6J mice bearing syngeneic Lewis lung carcinoma (3LL) and BALB/c mice with JW sarcoma (JWS). Mice were studied at different stages during tumor growth using microspheres labeled with 57Co (basal determination) or 58Co (after noradrenaline or saline). In control C57BL/6J mice noradrenaline induced a redistribution of CO, with an increase in the heart and brain and a decrease in the kidneys and hind limb muscle CO fractions (%CO). In 3LL-bearing mice the %CO to the tumor was not changed by noradrenaline 1 week after implantation but was significantly less after 2 and 3 weeks. %CO to the total lung tissue or to isolated metastases did not change after noradrenaline. In control BALB/c mice noradrenaline increased the %CO to the brain and decreased that to the kidneys and hind limb muscle. In JWS-bearing mice the %CO to the tumor was reduced 2 weeks after implantation, was not changed after 4 weeks and was increased after 6 weeks. These results suggest that tumor vessel reactivity to a vasoactive substance may change markedly during various phases of tumor growth and may differ in different experimental models.
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