title: Regional blood-to-tissue transport in RT-9 brain tumors.
abstract: Regional blood-to-tissue transport, expressed as a unidirectional transfer rate constant (K), was measured in experimental RT-9 brain tumors using 14C-alpha-aminoisobutyric acid (AIB) and quantitative autoradiographic techniques. The magnitude of K depends on the permeability, surface area, and blood flow of the tissue capillaries. The transfer rate constant was variable within tumor tissue (range 0.001 to 0.178 ml/gm/min) and depended on tumor size, location (intraparenchymal, meningeal, or choroid plexus associated), and to a lesser extent on necrosis and cyst formation. Brain adjacent to tumor had higher K values, particularly around larger tumors (0.004 to 0.014 ml/gm/min), than corresponding brain regions in the contralateral hemisphere (0.001 to 0.002 ml/gm/min). Estimates of the fractional extraction of AIB by intraparenchymal tumors were between 0.008 and 0.4 ml/gm/min. Values of fractional extraction in this range indicate that tumor capillaries are not freely permeable to this solute. The values of K measured with AIB in this study, for the most part, approximate the permeability-surface area product of tumor and brain capillaries. The experimental data suggest that the permeability-surface area characteristics of the microvasculature in small RT-9 tumors are similar to those of the host tissue, whereas the microvasculature of larger RT-9 tumors is influenced more by intrinsic tumor factors.
mesh_terms: D000621:Aminoisobutyric Acids; D000818:Animals; D001345:Autoradiography; D001692:Biological Transport; D001812:Blood-Brain Barrier; D001932:Brain Neoplasms / Q000098:blood supply*; D002831:Choroid Plexus; D006624:Hippocampus; D008770:Methylnitrosourea; D009374:Neoplasms, Experimental / Q000098:blood supply* / Q000139:chemically induced; D051381:Rats; D011916:Rats, Inbred F344; D013346:Subarachnoid Space; D014018:Tissue Distribution
chemical_list: D000621:Aminoisobutyric Acids; C100049:2-aminoisobutyric acid; D008770:Methylnitrosourea