Thermal trauma alters myocardial cyclic nucleotides and protein content in mice

1. This study tested the hypothesis that the systemic effects of burn include altered metabolic activity in the heart. Metabolic activity was studied by measuring alterations in cyclic nucleotide levels and protein concentrations in atrial and ventricular muscle in mice at 14 and 22 days after a 20% body surface area (BSA) burn. Thermal injury was produced on the dorsal surface of anesthetized male CD mice by immersion in water at 95 degrees C for 8 s. This resulted in a full-thickness, 3 degrees scald burn. In atrial and ventricular tissues, levels of adenosine 3':5'-cyclic monophosphate (cyclic AMP) and guanosine 3':5'-cyclic monophosphate (cyclic GMP) were analyzed by 125I-radioimmunoassay. 2. The protein content (mg prot g-1 dry wt) increased in the atria. The cyclic AMP content (nmol g-1 dry wt) was significantly increased fourfold and ninefold at 14 and 22 days, respectively, in atria from burned animals compared to controls. The cyclic AMP/cyclic GMP ratios were similarly increased. 3. In the ventricle, the protein content and cyclic AMP levels were not altered, but the cyclic AMP/cyclic GMP ratios (nmol g-1 dry wt) were increased at both 14 and 22 days. These changes both in atria and ventricles were less prominent when cyclic nucleotide concentrations or ratios were expressed as pmol mg-1 protein. 4. The data confirm the hypothesis that a 20% BSA thermal injury evokes effects in sites remote from burn injury such as in the atria and ventricles. These effects include total body weight loss, elevated cyclic AMP, cyclic AMP/cyclic GMP ratios, and protein levels in the atria, and elevated cyclic AMP/cyclic GMP ratios in both atrial and ventricular tissues at 2 and 3 weeks after thermal injury. To prevent underestimation of cyclic nucleotide levels such changes should preferably be expressed on a prot g- dry weight basis.