The effects of hyperoxic and hypercarbic gases on tumour blood flow.

Journal Article

Carbogen (95% O2 and 5% CO2) has been used in preference to 100% oxygen (O2) as a radiosensitizer, because it is believed that CO2 blocks O2-induced vasoconstriction. However, recent work suggests that both normal and tumour arterioles of dorsal flap window chambers exhibit the opposite: no vasoconstriction vs constriction for O2 vs carbogen breathing respectively. We hypothesized that CO2 content might cause vasoconstriction and investigated the effects of three O2-CO2 breathing mixtures on tumour arteriolar diameter (TAD) and blood flow (TBF). Fischer 344 rats with R3230Ac tumours transplanted into window chambers breathed either 1%, 5%, or 10% CO2 + O2. Intravital microscopy and laser Doppler flowmetry were used to measure TAD and TBF respectively. Animals breathing 1% CO2 had increased mean arterial pressure (MAP), no change in heart rate (HR), transient reduction in TAD and no change in TBF. Rats breathing 5% CO2 (carbogen) had transiently increased MAP, decreased HR, reduced TAD and a sustained 25% TBF decrease. Animals exposed to 10% CO2 experienced a transient decrease in MAP, no HR change, reduced TAD and a 30-40% transient TBF decrease. The effects on MAP, HR, TAD and TBF were not CO2 dose-dependent, suggesting that complex physiologic mechanisms are involved. Nevertheless, when > or = 5% CO2 was breathed, there was clear vasoconstriction and TBF reduction in this model. This suggests that the effects of hypercarbic gases on TBF are site-dependent and that use of carbogen as a radiosensitizer may be counterproductive in certain situations.

Full Text

Duke Authors

Cited Authors

  • Dunn, TJ; Braun, RD; Rhemus, WE; Rosner, GL; Secomb, TW; Tozer, GM; Chaplin, DJ; Dewhirst, MW

Published Date

  • April 1999

Published In

Volume / Issue

  • 80 / 1-2

Start / End Page

  • 117 - 126

PubMed ID

  • 10389987

International Standard Serial Number (ISSN)

  • 0007-0920

Digital Object Identifier (DOI)

  • 10.1038/sj.bjc.6690330

Language

  • eng

Conference Location

  • England