ULTRASTRUCTURAL AND CYTOCHEMICAL OBSERVATIONS ON B-16 AND HARDING-PASSEY MOUSE MELANOMAS THE ORIGIN OF PREMELANOSOMES AND COMPOUND MELANOSOMES

Abstract

The B-16 and Harding-Passey mouse melanomas were studied by light microscopy (tyrosinase, acid phosphatase, aryl sulfatase, thiamine pyrophosphatase and inosine diphosphatase activities) and electron microscopy (morphology and tyrosinase and acid phosphatase activities). Lysosomal enzyme activity is present in individual premelanosomes and melanosomes as well as in compound melanosomes. Acid phosphatase and tyrosinase activities are present in a Golgi-associated system of smooth endoplasmic reticulum (GERL) and small vesicles related to it. The acid phosphatase and tyrosinase activities of premelanosomes, and morphologic appearances, support the hypothesis that the granules arise from GERL. On the basis of the evidence presented, it is suggested that compound melanosomes arise within melanoma cells by autophagy.