EFFECTS OF THEOPHYLLINE ON THE SELECTIVE INCREASES IN INTRATUMORAL BLOOD-FLOW INDUCED BY INTRACAROTID INFUSION OF ADENOSINE AND ADENOSINE-TRIPHOSPHATE IN C6 GLIOMA-TRANSPLANTED RAT BRAINS

We have previously reported that the intracarotid administration of adenosine or adenosine triphosphate (ATP) selectively increased blood flow in intracerebrally transplanted C6 glioma cells in rats, using the hydrogen clearance method. In the present paper, we studied the difference between the effects of adenosine and ATP, using theophylline, a P1 purinoceptor blocker. The selective enhancement of the tumor blood flow by intracarotid administration of adenosine ws almost totally inhibited by theophylline. In contrast, the selective enhancement by ATP was shown definitely not to be inhibited by theophylline. Therefore, it is supposed that the selective increase of intratumoral blood flow by the intracarotid infusion of adenosine is closely related to the P1 purinoceptor, and the effect of the intracarotid infusion of ATP is composed not only of the effect as degraded into adenosine but also of the effect of ATP itself.