RESPONSE OF TUMOR RED-BLOOD-CELL FLUX TO ORGANOCOBALT(III) COMPLEX ADMINISTRATION

Cobalt(III)-containing compounds have demonstrated specific hypoxic ra diosensitisation in murine tumors. Our experiments have shown that an organocobalt(III) complexes with tridentate Schiff bases (RCo) are abl e to sensitize rodent tumors when given in combination with heating an d/or radiation/platidiam. It was proposed that RCo may enhance the ant itumor effect of conventional anticancer means due to formation of fre e radicals under an acid micromilieu in tumor tissue (in accordance wi th their chemical peculiarities). At the same time, it was known that some simple cobalt compounds (chloride, citrate, and salicylate) dilat e the blood vessels and decrease the blood pressure by about 10 mmHg. Our present study was aimed to evaluate the effect of iso-propylcobalt (III) (IIIb) complex on circulatory parameters in tumor tissue of the rat. It was shown that IIIb complex non-significantly reduced the mean arterial blood pressure to a minimum value of 130 +/- 15 mmHg 10 min after the injection (pretreatment value of 140 +/- 10 mmHg), with reco very thereafter to 145 +/- 8 mmHg at the 90th min after the injection. IIIb complex resulted in an initial rapid decrease in tumor red blood cell flux through tumor tissue which reached a minimum of 62% of the pretreatment value during the first 10 min following the injection. Th ereafter, tumor red blood cell flux rose until it reached a level 80% of the pretreatment value 90 min after the injection. It can be suppos ed that all cobalt-containing compounds may result in the inhibition o f tissue perfusion due to the influence of cobalt ions on blood pressu re by the dilatation of blood vessels. This circumstance must be taken into account under the investigation of cobalt(III) containing substa nces as radiosensitizers or bioreductive drugs.