Selective drug-induced reduction of blood flow in tumor transplants

The effect of a calcium antagonist and a physiologic amine on tumor and muscle perfusion was investigated with the aim of improving the preconditions for external hyperthermia treatment of cancer. Nisoldipine (0.04–4.0 mg/kg) and 5-hydroxy tryptamine (5-HT) (0.2–8.0 mg/kg) were administered i.p. in Sprague-Dawley rats bearing Walker 256 carcinoma, Yoshida sarcoma, or a homologous tumor transplant derived from a spontaneous leiomyosarcoma of the uterus. At the maximum dosage used, nisoldipine injection caused a decrease of the regional washout rate of Xenon-133 of 63 ± 8% (SEM) in the Walker carcinoma and an increase of 80 ± 41% in the muscle of the hind leg. 5-HT (8 mg/kg) caused a drop of 79 ± 29% in the Walker carcinoma and only a slight fall of the washout rate in muscle of 14 ± 4.8%. Tumor-to-muscle uptake ratios of 11C-butanol fell from 5.63 ± 1.98 to 3.32 ± 1.21, and from 5.3 ± 0.56 to 2.98 ± 0.30, after injection of 0.2 mg/kg nisoldipine and 4 mg/kg 5-HT, respectively. Similar reaction patterns and percentage changes were observed in different tumor lines at constant doses of 0.2 mg/kg nisoldipine and 4 mg/kg 5-HT. Both drugs representing two different rationales of vasomotor action were able to reduce blood flow specifically in transplanted tumors; nisoldipine increased muscle blood flow and decreased arterial blood pressure, whereas 5-HT acted without substantial systemic effects.