IS A CLINICAL-APPLICATION OF HYBRID LIVER SUPPORT SYSTEMS LIMITED BY AN INITIAL DISORDER IN CELLULAR AMINO-ACID AND ALPHA-KETO ACID METABOLISM, RATHER THAN BY LATER GRADUAL LOSS OF PRIMARY HEPATOCYTE FUNCTION

The in-vitro amino acid (AA) and alpha-keto acid (KA) metabolism of bi oreactors initially seeded with 2.5x10(9) pig hepatocytes was investig ated with a perfusion technique. Considerable changes in the culture m edium concentrations of AA and KA were measured during the first days in culture. This is indicative of dynamic cellular metabolism in the i nitial phase. While the concentration of pyruvate decreased starting o n the first day, alpha-ketoglutarate, alpha-ketoisocaproate, alpha-ket oisovalerate, and alpha-keto-beta-methyl-n-valerate were synthesized. The long term use of hepatocyte cultures in bioreactors and thus a des irable clinical hybrid liver support therapy appears to be possible si nce the hepatocytes switched, after 15 days in culture, to steady stat e conditions with a stable amino acid turnover featuring general AA up take accompanied by KA release. The release of branched chain KA, in p articular that of alpha-ketoisocaproate, reflects an effective transam ination activity in the bioreactor system. Primary pig hepatocytes cul tivated in hybrid liver support systems for therapy of acute liver fai lure or as devices for bridging to liver transplantation can sustain a mino acid metabolism for at least 30 days in vitro. However, an initia l disorder following the cell isolation that is demonstrated may limit immediate utilization of the systems prior to the reorganisation of t he cells to tissue-like structures in bioreactors.