Acta histochem. 81, 149-153 (1987) VEB Gustav Fischer Verlag Jena Departments of Anatomyl) and Biochemist ry2), The Chinese University of Hong Kong, Shatin, Hong Kong, and Department of Anat omy3), Sun Yat Sen Medical University, Guangzhou, China Optic nerve transection and tectal removal affect phagocytic activity of the pigment epithelium in goldfish By WINNIE W. Y. LIl), BETTAS. W. HUll), DAVID S. C. TSANG 2 ), and DAVID T. YEW l ),3) With 5 Figures (Received December 12, 1985) Summary The phagocytic ability of the pigment epithelium after optic nerve sectioning and tectal removal was investigated in the goldfish by the method of ingestion of latex beads. 4 days after sectioning, an increase in latex beads was evident which decreased by the end of first week. Tectal removal also triggered increase intake of latex beads which was presented after 7 days. Introduction The ability of the pigment epithelium to phagocytise is crucial to normal retinal functions and this activity is closely assiciated with outer segment shedding in the eye. Studies indicate that the phagocytic activity of the pigment epithelium appears to parallel the establishment of the visual cells (KUWABARA and WEIDMAN 1974). In the guinea pig, phagocytosis of the pigment epithelium is present in utero (SPIRA and HUANG 1978); while in the rat (YEW et al. 1985) and the frog (HOLLEYFlELD and WARD 1974), the ability to phagocytise appears before the visual cell development and the activity increases as the retina matures (YEW et al. 1985). In addition, phago- cytosis is believed to be triggered by or related to light stimulation (LA V AIL 1976). However, the relationship between phagocytic activity and the state of the visual cells remains unknown. For example, it is still unclear what would happen to the pig- ment epithelial activity once the retina starts to degenerate. Recently, we have report- ed that in the rat 6 days after optic nerve sectioning, there is a decrease in phago- cytic activity of the pigment epithelium suggesting that the phagocytic activity and the state of the retinal cells is closely related (YEW et al. 1985). In this communication we wish to report a more detail study between these two events in goldfish. Goldfish was chosen because of its dark and easily identifiable pigment epithelium and the large size of the eye. As described before, the uptake of the injected latex was used to monitor the rate of phagocytosis (EDWARD and SZAMlER 1977; YEW et al. 1985). Materials and methods Goldfish (Carassiu8 carassius) of an average length of 7 em obtained from a local aquarium farm were used in this study.