leupeptins and Bacterial-Infections

We investigated the influence of leupeptin (LP) intraperitoneal injection (40 mumol/2 days) on protein and amino-acid metabolism of septic rats (cecal ligation). All septic rats lost weight (-17 +/- 4 g), which was not prevented by LP administration (-24 +/- 1.8 g, n.s.). LP injection evoked weight loss even in normal rats (p less than 0.05 vs controls). Weight loss was accompanied by enhanced urinary nitrogen losses in all three groups. LP reduced food intake for 47% in control rats. Cecal ligation, and also the administration of LP, led to alterations of amino-acid metabolism. The most important changes were found in muscle free amino-acid concentrations with highly decreased levels of free glutamine. A glutamine deficiency is known to be related to a decreased rate of protein synthesis. The proteolytic rate in incubated soleus muscle was increased for 11.5% and even higher in LP-treated septic rats (+22%). It is concluded that the administration of LP cannot reverse protein catabolism in sepsis--possibly because LP does not influence those enzymes or proteases involved in tissue loss, or LP is inactivated by enzymes in rat tissues.

Topics: Amino Acids; Animals; Bacterial Infections; Body Weight; Eating; Leupeptins; Liver; Muscles; Oligopeptides; Proteins; Rats; Rats, Inbred Strains; Tyrosine

Topics: Animals; Bacterial Infections; Body Weight; Creatinine; Leupeptins; Liver; Male; Muscles; Oligopeptides; Rats; Rats, Inbred Strains; Tyrosine

The mechanisms of accelerated skeletal muscle protein degradation during sepsis have not been fully elucidated. Activity of the lysosomal protease cathepsin B is increased in skeletal muscle during various catabolic states other than sepsis. In the present study the protein degradation rate and cathepsin B activity were determined in extensor digitorum longus and soleus muscles from nonseptic and septic rats. The protein degradation rate during incubation in vitro with or without the cathepsin B inhibitor leupeptin was also determined. Both protein degradation and cathepsin B activity were increased in muscles from septic rats. Incubation with leupeptin reduced, but did not normalize, the protein degradation rate in both extensor digitorum longus and soleus muscles from septic animals. These studies suggest that increased cathepsin B activity contributes to the accelerated muscle proteolysis seen during sepsis and that proteases other than cathepsin B are also involved.

Topics: Animals; Bacterial Infections; Cathepsin B; Leupeptins; Male; Muscle Proteins; Muscles; Rats; Rats, Inbred Strains

The roles of prostaglandins and lysosomal proteases in accelerated skeletal muscle proteolysis during sepsis are not yet fully understood. In this study rats received intraperitoneal injections of the prostaglandin synthesis inhibitor indomethacin (IND, 5.0 mg/kg), the lysosomal cathepsin B inhibitor leupeptin (LEU, 2.5 mg/kg), or normal saline 2 hr before cecal ligation and puncture (a model of intraabdominal sepsis) or sham-operation. The injections were repeated every 6 hr for a total of four doses. Sixteen hours after operation, intact extensor digitorum longus (EDL) muscles were harvested and cathepsin B activity was measured in one muscle. The contralateral muscle was incubated in oxygenated Krebs-Henseleit bicarbonate buffer containing glucose (10 mM) and cycloheximide (0.5 mM), and protein degradation rate was determined as the release of tyrosine into the incubation medium. Both muscle cathepsin B activity and protein degradation rate were higher in septic than in sham-operated rats. Treatment with IND or LEU significantly reduced the elevated cathepsin B activity in septic muscles, but failed to significantly alter muscle proteolysis. In nonseptic muscle, both cathepsin B activity and protein degradation rate were unaffected by the different types of treatment. The results suggest that although prostaglandins may influence muscle lysosomal protease activity, neither prostaglandins nor the lysosomal protease cathepsin B appear to be major regulators of accelerated muscle protein breakdown during sepsis.

Topics: Animals; Bacterial Infections; Cathepsin B; Indomethacin; Leupeptins; Muscle Proteins; Muscles; Oligopeptides; Reference Values