Novel Flushing Provoked by Volatile Anesthetics in Mastomys natalensis Bearing a Transplantable Substrain of Gastric Carcinoid That Predominantly Secretes Serotonin

A tumor substrain secreting a large amount of serotonin [5-hydroxytryptamine (5-HT); CAS: 50-67-9; 3-(2-amino-ethyl)indol-5-ol] and a minute amount of histamine (CAS: 51-45-6) has been isolated from the previously established strain of transplantable gastric carcinoid of Mastomys (Praomys) natalensis secreting both histamine and 5-HT. Mastomys bearing a large growing transplant and excreting a large amount of 5-hydroxy-indoleacetic acid [(5-HIAA) CAS: 54-16-0] were associated often with reddening of the nose, lower lip, auricles, hands, and feet. Soon after the animals were anesthetized by ether or other volatile anesthetics, the tinges of red of the above-mentioned exposed parts abruptly turned bright red and rapidly spread over the neck, upper chest, and epigastric area. The reddening was transient, lasting 1.5-5 minutes, thereby fulfilling the criteria of flushing. The severity of ether-provoked flushing in tumor-bearing Mastomys paralleled the urinary excretion levels of 5-HIAA. The ether-provoked flushing was prevented completely by sc injection of either ketanserin (150 micrograms) or somatostatin (20 micrograms). The same ether-provoked flushing as found in tumor-bearing Mastomys could be reproduced in normal ones by constant infusion of 20 mg 5-HT/kg/24 hours (i.e., doses comparable to those released from a transplanted tumor) through an osmotic minipump implanted subcutaneously.