A new method was developed for assay of
guanase activity by direct colorimetric determination of
ammonia. In this method, dotite
bicine buffer is used for preparation of a stable substrate
solution and with a fixed concentration of substrate of sufficient strength serum
guanase can be measured sensitively and reproducibly. This assay system could be used as a routine clinical laboratory test in the diagnosis of liver damage. GOT, GPT and
guanase activities were found to be significantly elevated in patients with various liver disorders, and those with acute
myocardial infarction with prominent congestion of the liver and also in CCl4- treated dogs. However, serum
guanase activity was normal in patients with various other diseases, in those with acute
myocardial infarction and in dogs with experimental
myocardial infarction without liver damage, even when the serum GOT and GPT activities were increased. The GOT, GPT and
guanase in the medium of rat hepato cytes culture with 5.0 mM CCl4 were elevated. These findings suggest that serum
guanase activity is a more specific
indicator of liver damage than serum GOT and GPT. The determination of serum
guanase activity in patients without liver damage, even when their serum GOT and GPT levels elevated, might be useful as a screening test of liver damage.