Tyrosinase and Acid Phosphatase Activities in Melanocytes from Avian Albinos

Two forms of cutaneous albinism in the chicken were investigated for the presence and distribution of tyrosinase and acid phosphatase in melanocytes in situ and in culture. In sex-linked recessive tyrosinase-positive albinism, Sal, melanocytes in regenerating feathers and neural tube-derived cultures contained morphologically normal and abnormal premelanosomes. Tyrosinase was localized primarily to the abnormal premelanosomes and probably not to the normal ones. The cells possessed, in addition, vacuoles with membranous inclusions, located in the dendrites, and capped by dopa-positive vesicles (capping yes-ides). Acid phosphatase colocalized with tyrosinase in the abnormal primelanosomes and capping vesicles. Tyrosinase activity in extracts of cultured Sal melanocytes equalled that of e+ control melanocytes. A tyrosinase antiserum, raised against hamster tyrosinase (Pomerantz), precipitated 2 proteins, 68 kD and 82 kD, which had a precursor-product relationship. The amount immunoprecipitate was the same in Sal and control extracts, but in Sal extracts the lower-molecular-weight protein was twice as abundant as the higher-molecular-weight protein. Melanocytes in regenerating feathers from an autosomal recessive, tyrosinase-negative albino, ca, also contained morphologically normal and abnormal premelanosomes. In culture, ca melanocytes had no formal premelanosomes but only dopa-negative multivesicular bodies with wispy filamentous material. Tyrosinase activity and immunoprecipitable tyrosinase were absent. These results suggest that: (1) the tyrosinase-positive albino, Sal, has an aberration in both its tyrosinase and acid phosphatase profiles and (2) the tyrosinase-negative albino, ca, lacks functionally and antigenically normal tyrosinase.