PROLONGED CHANGES IN PROTEIN AND AMINO-ACID-METABOLISM AFTER ZYMOSAN TREATMENT IN RATS

1. Intraperitoneal injections of zymosan were given to rats, according to a modified procedure, in order to create a pattern of illness with an acute critical phase for 36 h followed by a prolonged recovery pha se lasting for at least 10 days. Changes in amino acid and protein met abolism were studied in both phases. 2. Differences between this modif ied and the original zymosan model are a lower mortality (16%), which is limited to the first 36 critical hours, and the absence of signs of severe illness during the prolonged recovery phase. 3. Wasting of mus cle protein and decreased protein synthesis rates in muscle were obser ved during the acute phase of illness. Liver size and liver protein sy nthesis rates were increased during the same period. The decrease in t he total amount of muscle protein and the increase in liver weight wer e still present 12 days after zymosan treatment, despite a normalizati on of protein synthesis rates. Large decreases were observed in the co ncentrations of the conditionally essential amino acids glutamine and arginine in muscle over 6 days. Decreases in plasma glutamine and argi nine on day 12 after zymosan indicated that the rats were still not fu lly recovered on this day. 4. We conclude that injection of a single d ose of zymosan in rats leads to metabolic derangements both during the acute phase of critical illness and during the prolonged recovery pha se. The model seems suited for investigating the biochemical mechanism s behind these metabolic derangements and for studying therapeutic and nutritional interventions during recovery from critical illness.