Intracellular Localization and Secretion of Naphthoquinone Pigments in Cell Cultures of Lithospermum erythrorhizon

Abstract

The intracellular localization and secretion process of naphthoquinone pigments (shikonin derivatives) in cell cultures of Lithospermum erythrorhizon were investigated chiefly by electron microscopy. The results have suggested that the pigments accumulate in “secretion vesicles” which originate from electron dense, spherical swellings formed in highly elongated, rough endoplasmic reticula. Most of these vesicles appeared to fuse with the plasma membrane to secrete the contents consisting mainly of shikonin pigments, lipids, and proteins to the outside of the cell wall.