Effects of choline chloride on the pigment translocation within fish melanophores

Abstract

1. Effects of choline chloride on melanophores were studied in split-fin preparations of the tilapia. 2. In a saline solution in which NaCl was totally or partially replaced by choline chloride, norepinephrine-induced (NE-induced) aggregation of melanosomes was inhibited in a dose-dependent manner. 3. The pigment-aggregating response of melanophores to NE was unchanged in sodium-free solution that had been prepared by substituting KCl for NaCl. 4. The reversal of the response of melanophores to NE was accelerated by rinsing with the choline-rich solution. Propranolol, a beta-adrenergic antagonist, had no effect on this phenomenon. 5. These results suggest that choline itself may have a pigment-dispersing effect on fish melanophores. The site of its action may be within the melanophores.