© 1985 Oxford University Press
research-article |
Antihistamines Block Radiation-Induced Increased Intestinal Blood Flow in Canines1
Physiology and Biochemistry Departments, Armed Forces Radiobiology Research Institute Bethesda, Maryland 20814
Antihistamines Block Radiation-Induced Increased Intestinal Blood Flow in Canines. COCK-ERHAM, L. G., DOYLE, T. F., DONLON, M. A., AND GOSSETT-HAGERMAN, C. J. (1985). Fundam. Appl. Toxicol. 5, 597–604. Radiation-induced systemic hypotension is accompanied by increased intestinal blood flow (IBF) and an increased hematocrit (HCT) in dogs. Histamine infusion leads to increased IBF and intestinal edema with consequent secretion of fluid into the intestinal lumen. This study was performed to determine whether these effects could be diminished by prior administration of H1 and H2 histamine blockers. Dogs were given an iv infusion of mepyramine (0.5 mg/min) and cimetidine (0.25 mg/min) for 1 hr before and for 1 hr after radiation (H1 and H2 blockers, respectively). Mean systemic arterial blood pressure (MBP), IBF, and HCT were monitored for 2 hr. Systemic plasma histamine levels were determined simultaneously. Data obtained indicated that the H1 and H2 blockers, given simultaneously, were successful in blocking the increased IBF and the increased HCT seen after 100 Gy, whole-body, 
radiation. However, the postradiation hypotension was only somewhat affected, with the MBP falling to a level 28% below the preradiation level. Plasma histamine levels reached a sharp peak, as much as 20% above baseline, at 4 min postradiation. These findings implicate histamine in the radiation-induced increase in IBF and HCT but not for the gradual decrease in postradiation blood pressure