Immunological determination of tyrosinase in sera of melanoma-bearing hamsters.

The quantitative ring immunodiffusion technique was adapted for the determination of the DOPA-oxidase activity of tyrosinase [E.C.1.14.18.1] in the sera of melanotic melanoma-bearing hamsters. The smallest amount of tyrosinase detectable in antibody-agar plates was about 0.5 micrograms/ml. The quantity of tyrosinase in the hamster sera depended on the grade of tumor development and rose to a value of 40 microgram/ml. There was no detectable activity in the sera of hamsters without tumor. The possibility of using this method to test sera of patients and horses with melanoma malignum is discussed.