EFFECT OF HYDRALAZINE IN SPONTANEOUS TUMORS ASSESSED BY OXYGEN ELECTRODES AND P-31-MAGNETIC RESONANCE SPECTROSCOPY

Hydralazine can substantially decrease the blood flow, oxygen status a nd energy metabolism of transplanted tumours. In spontaneous tumours, two recent studies reported no effects of hydralazine on energy metabo lism measured by P-31-magnetic resonance spectroscopy (P-31-MRS), alth ough another study saw changes in oxygen partial pressure (pO(2)) dist ributions measured with electrodes. We have now performed P-31-MRS and pO(2) measurements in the same T138 spontaneous tumours, before and a fter intravenously (i.v.) injecting anaesthetised mice with 5 mg kg(-1 ) hydralazine. Tumour pO(2) was measured with an Eppendorf oxygen elec trode and P-31-MRS spectra obtained with a 7-tesla SISCO magnet. Of 12 tumours all showed an increase in the percentage of pO(2) values less than or equal to 5 mmHg after hydralazine treatment and 10/12 showed a decrease in median pO(2). The average (+/- 1 s.e.) values for the pe rcentage less than or equal to 5 mmHg went from 45% (+/-9) to 79% (+/- 5) and the median from 9 mmHg (+/- 2) to 2 mmHg (+/- 1). With the P-31 -MRS 8/12 rumours showed an increase in the ratio of the peaks of inor ganic phosphate to beta-nucleoside triphosphate with the average (+/- 1 s.e.) values going from 1.1 (+/- 0.2) to 2.4 (+/- 0.9). Thus spontan eous tumours can respond to hydralazine and do so in a way consistent with that reported for transplanted tumours.