The Protective Effect of Guanylic Acid against Isoproterenol Toxicity ∗

Summary

Subcutaneous injections of isoproterenol in rats produces myocardial edema and other histologic evidence of toxicity. If guanylic acid is injected daily for 7 days preceding the administration of isoproterenol there is significantly less cardiac muscle edema and the cardiac index (heart weight/body weight) is lowered. Similar pretreatment with adenylic acid had no effect. When bilateral or unilateral hind limb tourniquet is added to the stress of isoproterenol injection the survival time of the animals following tourniquet removal is markedly decreased. Seven days of pretreatment with guanylic acid significantly extended the survival time of these doubly stressed animals. Again, adenylic acid was without effect. It is suggested that guanine nucleotides may be utilized to a greater degree during severe stress and administration of exogenous guanine nucleotides may produce more effective protein anabolism under these circumstances.