• Muscles from fed or 72-hour fasted rats were incubated in the presence of plasma from septic rats, recombinant interleukin 1α (rIL-1α), or recombinant tumor necrosis factor α (rTNFα), 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 1α or recombinant tumor necrosis factor α 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.
(Arch Surg. 1990;125:510-514)