In vivo incorporation of [3H]leucine and [3H]tyrosine by caudal neurosecretory cells of the trout Salvelinus fontinalis in relation to osmotic manipulations. A radioautographic study

The in vivo incorporation of tritiated leucine and tyrosine during various time intervals by caudal neurosecretory cells of trout Salvelinus fontinalis was studied quantitatively with light microscopic radioautography in relation to osmotic manipulations. The [³H]leucine labeling in fish exposed to deionized water for 3 days was much higher than in fish kept in fresh water, indicating enhanced synthetic activity. Under both conditions, the maximum of incorporation was observed 12 hr after injection of the tracer. The reduced radioautographic reaction noted at 24 hr suggested a rapid transit of newly synthesized proteinaceous material from cell body cytoplasm toward the axonal compartment. [³H]Tyrosine was incorporated to a greater degree than [³H]leucine in cells of fish in fresh water. The varied synthetic activities exhibited by caudal neurosecretory cells in response to osmotic stimuli indicate possible participation by these cells in osmotic and ionic regulation.