ABSTRACTStudies were made on why glycyrrhizin injection decreases the plasma aspartate aminotransferase (AST) and alanine aminotransferase activities in patients with chronic hepatitis.1For this, rat hepatocytes were isolated, and incubated with antibody raised against rat liver cell membranes, and the effect of glycyrrhizin on their release of transaminase was investigated. Isolated rat hepatocytes released AST on incubation with anti‐liver cell antibody in the presence of complement. At this time, their endogenous phospholipase A2activity was increased. Cultured hepatocytes also released the transaminase in the presence of venom phospholipase A2. Glycyrrhizin suppressed the release of transaminase in the presence of either anti‐liver cell membrane antibody or phospholipase A2. These results suggest that antibody treatment raised the phospholipase A2activity in liver cell membranes, resulting in release of transaminases, and that glycyrrhizin suppressed this increase in phospholipase A2activity and so inhibited the release of transamin