Abstract
ObjectiveTo study blood flow, vascular volume and arterio-venous passages in induced mammary tumours of the rat to characterize parameters possibly responsible for tumour hyponutrition. MethodDimethylbenzanthracene-induced mammary tumours in Sprague-Dawley rats were studied. Regional blood flow was studied by use of the radioactive microsphere tracer technique using 141Cerium-labelled 15μm spheres coinjected into the left cardiac ventricle with 125Iodine-labelled 25μm spheres. Blood volume was studied by use of 125Iodine- or 99mTechnetium-labelled human serum albumin, the latter allowing autoradiography of tumour sections for visualization of flow and volume. ResultsTwenty-seven rats with 170 tumours had a mean tumour blood flow of 48 and 67mL×min−1×100g−1 using 15 and 25μm sphere data, respectively, indicating a significant passage through vessels between 15 and 25μm. The lungs showed a “nominal bronchial” blood flow of 260 and 135mL×min−1×100g−1 for the 15 and 25μm spheres, respectively, indicating pulmonary trapping, particularly of small spheres passing the systemic circulation in vessels larger than 15μm. There was a positive correlation between the total tumour blood flow within individual rats and trapped spheres of both dimensions in the lungs, indicating shunts also larger than 25μm.Normal tissues disclosed only small differences in regional blood flow as measured by the two spheres.Blood volume was studied in 20 rats with 120 tumours, with a vascular volume of 3.6mL×100g−1 representing a blood turnover >15 times/min. Blood volume co-localized with perfusion as seen in autoradiographs. ConclusionIn induced rat mammary tumours, a high fraction of blood, 28%, passes arterio-venous vessels between 15 and 25μm and there also exist passages >25μm. These findings indicate that the functional capacity of the tumour vascular bed might be impaired, adding to the abnormal microenvironment of tumours.
Published Version
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