Mechanisms of radio-protection by catecholamines in the hamster (Mesocricetus auratus).

Whole-body exposure to 1000 or 2000 rads in a 60Co source was used to study radio-protection by norepinephrine, isoproterenol, and phenylephrine in normal and splenectomized hamsters. After exposure, the animals were caged individually, and percent survivals were recorded daily. The aortic blood pressure of permanently cannulated, unanaesthetized hamsters was measured to test the vasoconstriction-hypoxia mechanism of radio-protection, and plasma calcium levels were measured to test the hypothesis that isoproterenol protects through a mechanism of hypercalcaemia-stimualted cell proliferation. The data support the vasoconstriction-hypoxia mechanism for agents stimulating the alpha receptors, while beta agonists seem to protect through a hypotensive-hypoxia mechanism similar to that of histamine. All the catecholamines protect against the haematopoietic syndrome, but show no evidence of protection against the gastrointestinal syndrome.