The effect of dexamethasone on the occurrence and ultrastructure of rodlet cells in goldfish

In the bulbus arteriosus of goldfish Carassius auratus a subendothelial "reticular space" was comprised of reticular-like cells, neutrophils, medium-sized granular leucocytes, phagocytes, endothelial cells and reticulo-endothelial cells; herein, rodlet cells (RCs) accumulated and probably matured. Four classes of RCs were identified: (1) Those occurring in the "reticular space" and contacting reticular-like cells; (2) those present in the "reticular space" contacting reticular-like and endothelial cells; here the RCs were discharging; (3) those occurring in the bulbar lumen anchored to lining endothelial cells or other RCs; (4) those free in the bulbar lumen. There was no significant difference in the number of RCs among control and saline- and dexamethasone-treated fish, but significant differences were found in RCs’ class partition and in their discharge modality. In dexamethasone-treated goldfish class (3) RCs were almost absent (2% v. 10% of the other experimental groups), moreover 35% of the RCs developed a “bleb” discharge modality rather than the most typical “koronenartigen konfiguration” which developed in the vast majority (90%) of the other experimental groups.