N-TERMINAL AND C-TERMINAL FRAGMENTS OF THE HORMONE STANNIOCALCIN SHOWDIFFERENTIAL-EFFECTS IN EELS

The effects of an N-terminal, a C-terminal, and a mid-fragment of stan niocalcin, the primary hypocalcemic hormone in fish, on plasma total a nd free (ionic) calcium levels and whole animal calcium influx were te sted in eels. Both the N- and the C-terminal fragments were hypocalcem ic, causing 18 and 12% reduction in plasma calcium in stanniectomized eels, respectively. With both fragments the hypocalcemic action is tra nsient. The hypocalcemia caused by the C-terminal fragment, although m ore rapid, is not as pronounced as the hypocalcemic action of the N-te rminal fragment. Only the C-terminal fragment reduced calcium influx. The hypocalcemic activity of the C-terminal fragment then can be expla ined by its effect on calcium influx. The N-terminal fragment appears to function in a different manner. The mid-fragment has no effect on p lasma calcium or calcium influx. The different parts of the hormone ar e concluded to have different effects. (C) 1995 Academic Press, Inc.