ACTH-induced internalization of plasma membrane in xanthophores of the goldfish, Carassius auratus L

The ACTH-induced pigment dispersion in primary cultures and in suspensions of xanthophores of the goldfish, Carassius auratus L., has been shown to include the formation of rosette-like membranous structures and plasma membrane invaginations (pits). The rosettes and pits are probably similar structures sectioned at different angles. Horseradish peroxidase studies demonstrate that these structures are eventually converted into small spherical vesicles and long smooth elements, similar in appearance to spherical and "tubular" endoplasmic reticulum, respectively. In addition, these studies show that once vesicles are formed they are no longer continuous to the outside of the cell.