A new model of lung metastasis for intravital studies

We created an experimental model of pulmonary metastasis based on subcutane ously implanted Lewis lung cancer in mice and observed in vivo the microcir culation of spontaneously metastasized tumors in the lung. The mice lung wa s held by a small handmade suction ring to stop cardiac and respiratory mov ement. Using fluorescent microscopy, tumor microcirculation and normal lung microcirculation in the same lung lobe were compared by measuring microves sel diameter and blood flow velocity [red blood cell (rbc) velocity]. In no rmal microcirculation, the mean values of microvessel diameter and rbc velo city were 10.4 +/- 2.7 mu m and 188 +/- 63 mu m/s, respectively. In tumor m icrocirculation, the mean values of the same were 10.6 +/- 3.3 mu m and 105 +/- 40 mu m/s. The rbc velocity in normal microcirculation was significant ly higher (P < 0.001) than that in tumor microcirculation. The calculated s hear rates of normal microcirculation and tumor microcirculation were 73.4 +/- 23.4 (/s) and 41.2 +/- 16.1 (/s), respectively. The shear rate of the t umor microcirculation was significantly slower (P < 0.001) than that of the normal microcirculation. We demonstrated a feasibility of observation and measurement of tumor microcirculation in the lung and confirmed that the ph ysiologic data were compatible to those in the brain or in the liver report ed by others. This model might be useful for studying metastatic tumor path ophysiology in the lung microcirculation. (C) 2000 Academic Press.