ELECTRON MICROSCOPIC DEMONSTRATION OF TYROSINASE IN PTERINOSOMES OF THE FROG XANTHOPHORE, AND THE ORIGIN OF PTERINOSOMES*

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Abstract
In the frog, Rana japonica, the successive appearance of types I, II and III pterinosomes, which were defined according to the degree of lamellar structure was in keeping with the xanthophore differentiation at the larval stage, but these 3 types coexisted in a single xanthophore in the adult. An intense tyrosinase reaction was found in type I-II intermediate form in the larval and adult xanthophores, but it was rarely observed in types I and III. A tyrosinase reaction was always found in the GERL (Golgi-associated endoplasmic reticulum) of larval and adult xanthophores, and it was similarly evident in small Golgi vesicles which were separated from the GERL and dispersed in the cytoplasm. Tyrosinase and pterinosome originated from different parts of the cytoplasm. The hypothesis that small Golgi vesicles were transported to the tyrosinase-negative premelanosomes involved in the origin of the melanosome was also applicable to the origin of pterinosomes.