Diaphragm acetylcholinesterase multimeric forms in mice in response to burn trauma

This report continues our investigations concerning relative changes in acetylcholinesterase (AChE) activity in response to burn trauma. This experiment was performed in mouse diaphragm. AChE is fundamental to the operating efficiency of the neuromuscular junction. It is through such junctions that all skeletal muscle contraction occurs. This paper tests the hypothesis that burn trauma induces changes in diaphragm AChE with respect to total content, specific molecular forms, and relationships of the polymorphic forms to each other. After mice were exposed to increasing size of body surface area (20%, 30%, and 50%) diaphragms were excised at 3 weeks after burn injury. AChE activity was measured by differential extraction and velocity sedimentation on sucrose gradients. In the sham-treated control groups most of the AChE activity consisted entirely (92%) of the globular forms (S1 and S2). Asymmetric (S3 and S4) and nonextractable (H5) forms made up 2% and 6% of the AChE activity, respectively. In the burn groups all total globular activity was decreased by 1/6 to 1/3 of control groups. For these groups the asymmetric forms (S3 and S4) were increased ninefold to fourteenfold. Nonextractable forms (S5) among the groups were not different. Individual soluble globular forms (S1: 4S, 6.5S, 10S) were reduced by 50% for only the 20% and 30% BSA groups. Residual globular forms (S2) were increased threefold to ninefold. Some of the asymmetric forms (S3: 4S, 10S, 12S, and 16S) were increased fivefold to eightfold among the burn groups. Residual asymmetric (S4) and nonextractable (S5) forms were not different. This report shows that in response to burn trauma the AChE activity of the diaphragm and the interdependence of the polymorphic forms were changed at the chronic postburn period. These findings may aid in understanding the adaptive response of diaphragmatic preservation in burn trauma.