The effects of prolactin, cortisol and calcium-free environment on water influx in isolated gills of Japanese eel, Anguilla japonica.

Abstract 1. The effects of prolactin, cortisol and a calcium-free environment on water influx into the isolated gills of the Japanese eel, Anguilla japonica were studied by an in vitro technique. 2. It was confirmed that the prolactin injection significantly reduced the water influx into the isolated gills and/or water permeability. Cortisol injection, on the other hand, increased the water influx and/or water permeability. 3. Calcium-free environments, deionized water and calcium-free sea water, served to increase the water influx and/or water permeability compared with its values in normal environments. 4. The possible roles of prolactin, cortisol and environmental calcium in the osmoregulation of the eel in fresh water and sea water are discussed.