A C-terminal fragment of the hormone stanniocalcin is bioactive in eels

An in vivo eel bioassay based on 45Ca uptake from the ambient medium was used to compare the activity of native trout and American eel stanniocalcin (STC) with that of a synthetic C-terminal fragment (AA 202-231; peptide W) of Australian eel STC. Qualitatively, the action of peptide W resembled that of purified native rainbow trout (Oncorhynchus mykiss) STC as well as fresh extracts of American eel Stannius corpuscles in that they all inhibited whole animal Ca2+ influx. This inhibition was observed in both intact and stanniectomized eels regardless of whether the eels were exhibiting high or low initial calcium uptake rates. These observations suggest that peptide W activates eel gill STC receptors. Further, as peptide W was previously reported to stimulate Ca2+ influx in intact rainbow trout fry, the present data provides evidence for a difference in the way this fragment functions in various species.