Is there a circulating proteolysis-inducing factor during sepsis?

Muscles from fed or 72-hour fasted rats were incubated in the presence of plasma from septic rats, recombinant interleukin 1 alpha (rIL-1 alpha), or recombinant tumor necrosis factor alpha (rTNF alpha), and breakdown of total and myofibrillar protein was assessed by determining release of tyrosine and 3-methylhistidine, respectively. Septic plasma stimulated total protein breakdown in muscles from 72-hour fasted rats by 10% to 20%, while myofibrillar protein breakdown was not affected. When septic plasma was added to muscles from fed rats, neither tyrosine nor 3-methylhistidine release was altered. Various concentrations of recombinant interleukin 1 alpha or recombinant tumor necrosis factor alpha did not affect total or myofibrillar protein breakdown. Since septic plasma did not stimulate myofibrillar protein breakdown, the role of a circulating factor for muscle proteolysis during sepsis remains unclear.