Neutral proteinase activity in skeletal muscle from thermally injured rats.

Male Sprague-Dawley rats that received 60% total body surface, full-thickness, scald burns on the dorsum and abdomen were used in this study. Neutral proteinase and Ca2+-activated neutral proteinase activities were measured in gastrocnemius and soleus muscles at 3 and 21 days after the thermal injury. Neutral proteinase activity decreased significantly in the soleus (50%) and gastrocnemius (46%) muscles on the third postburn day. Ca2+-activated neutral proteinase was unchanged at this time. Neutral proteinase and Ca2+-activated neutral proteinase activities were unaltered at 21 days postinjury. These results may reflect a protein-sparing effect on the third postburn day which could be an early intracellular change prior to an increase in selected enzyme proteins during the hypermetabolic phase after thermal injury.