Stable bioenergetic status despite substantial changes in blood flow and tissue oxygenation in a rat tumour

Abstract

al., 1985;Evelhoch et al., 1986;Tozer et al., 1987; Vaupel et al., 1989a, b;Steen & Graham, 1991 (Bremner et al., 1993). The reduction in the oxygenation status caused by hydralazine is insufficient for detection by 31P-NMR in human xenografted tumours, whereas in RIF-1, SCCVII/Ha and KHT murine tumours large increases in the Pi/total phosphate ratio are found (Bremner et al., 1991;Adams et al., 1992). In the light of these discrepancies, a number of relevant issues need to be clarified regarding the relationship between energy status and tumour blood flow. In the present study, the key questions were as follows:(1) Do nected to a ratemeter (FHT 1100 FAG Kugelfischer, Erlangen, Germany). The method of evaluation of TBF was identical to that described earlier (Kluge et al., 1992). Measurements were performed on tumours of varying sizes at 20 min intervals before application of TNF-x and at 30 min intervals thereafter over a total time period of 2 h post treatment. In all experiments performed in this study, animals were allowed to stabilise following the surgical procedures. Measurements commenced once constant baseline readings for MABP and flow were obtained for at least 20 min.Laser Dopplerflowmetry A Periflux model PF 3 dual-channel laser Doppler flowmeter was used for this study (2 mW He-Ne laser, wavelength 632.8 nm; Perimed, Stockholm, Sweden , 1989a, 1991). Measurements were made either on tumours of varying sizes or before and 120 min after acute flow changes upon TNF-a application.Measurement ofglobal concentrations of adenylate phosphates in perchloric acid extracts In order to obtain mean (global) levels of adenylate phosphates, the tumour-bearing hindfoot was rapidly frozen and the tumours (n = 12) were prepared under liquid nitrogen and stored at -80°C for further processing. In a first series of experiments, tumours of varying sizes were analysed. In another series, tumours were assayed before or 120 min after administration of TNF-o. Each deep-frozen tumour was ground to a fine powder and freeze dried. For determination of ATP, ADP and AMP levels, aliquots of freeze-dried tissue were extracted with 0.66 M perchloric acid, centrifuged and the supernatant neutralised with 2 M potassium hydroxide. The concentrations of the adenylate phosphates were then determined using reversed-phase high-performance liquid chromatography (HPLC) techniques at 254 nm (for more details see Kruger et al., 1991;Schaefer et al., 1993). Concentrations were expressed as j.mol per g tissue wet weight.Determination of microregional A TP distribution Before preparing the rapidly frozen tumours for HPLC analysis, approximately 30% of the tumour mass was separated, cut at -25°C in a cryostat into 5-nm sections and used for ATP bioluminescence measurements to assess the microregional ATP distribution using single-photon imaging and quantitative bioluminescence (for methodological details see Walenta et al., 1992;Schaefer et al., 1993). The spatial resolution gained by this method is about 50 jam, thus revealing informatio...

The effect of hypoxia and hyperoxia on nucleoside triphosphate/inorganic phosphate, pO2 and radiation response in an experimental tumour model

“…The low tumour oxygenation is likely to be a consequence of both the increase in carboxyhaemoglobin and the reduction in blood flow, whereas the intact energy metabolism is most probably explained by a sufficient supply of glucose and/or other nutrients for anaerobic glycolysis even under these conditions. This hypothesis is supported by other studies showing that the tumour bioenergetic status was dependent on alterations in blood flow, oxygen availability (Vaupel et al, 1994a) and nutritional resources to sustain the energy metabolism (Gerweck et al, 1993). Using an in vitro assay and a different tumour model, it was demonstrated that the energy status was stable during oxygen deprivation but with the availability of sufficient glucose (Gerweck et al, 1993).…”

Nifedipine improves blood flow and oxygen supply, but not steady-state oxygenation of tumours in perfusion pressure-controlled isolated limb perfusion

“…Although nifedipine application during ILP increased tumour perfusion by approximately 60% (Figure 3) and in turn the nutrient and oxygen supply, only the glucose concentration in the tumour was elevated. Nifedipine had almost no impact on the bioenergetic status, a finding which is in good accordance to an earlier study demonstrating the energy status to be relatively stable despite substantial changes in blood flow and tissue oxygenation providing tumour perfusion does not fall below a certain threshold (Vaupel et al, 1994).…”

“…However, the higher glycolytic rate had only a minor impact on the bioenergetic status resulting in ATP levels which are comparable to those found previously in untreated tumours (Vaupel et al, 1994). Although nifedipine application during ILP increased tumour perfusion by approximately 60% (Figure 3) and in turn the nutrient and oxygen supply, only the glucose concentration in the tumour was elevated.…”

In vivo 31P magnetic resonance spectroscopy and morphometric analysis of the perfused vascular architecture of human glioma xenografts in nude mice

“…They argued that (an)aerobic glyco lysis is capable of maintaining the energy status. In vivo (DS sarcoma), Vaupel et al (1994) reported that after reduction of the tumour blood flow the amount of NTP remains nearly constant. These findings were explained by an intensified glycolysis due to the recruitment of glucose from the interstitial reservoir of the tumour.…”