The effect of nicotinamide on microregional blood flow within tumours assessed using laser Doppler probes

Laser Doppler probes have been used to provide real-time spatial flow mapping of microregional erythrocyte flux within the murine Sarcoma F (SaF). The results demonstrate that fluctuations in microregional red blood cell flux are a common feature of SaF tumours, with approximately 50% of regions demonstrating a change of at least a factor of 2 over a one-hour sampling period and 16% of regions showing a greater than 5-fold change. Administration of 250 mg/kg nicotinamide induced a small reduction in the number of microregions showing fluctuations, 9% of regions demonstrated large fluctuations (i.e., > or = 5) relative to 16% in control tumours. At a dose of 500 mg/kg, the number of changes in microregional erythrocyte flux was increased. However, unlike either untreated or nicotinamide 250 mg/kg pretreated animals, these changes were mostly increases in microregional flow. Indeed, 12 of the 13 changes by a factor of 5 or greater, observed following nicotinamide at 500 mg/kg, were increases. This effect on microregional flow translated into only a 25% increase in macroregional flow determined by averaging all the regions sampled.