TRH stimulates the release of POMC-derived peptides from goldfish melanotropes

Abstract

The release of immunoreactive (ir) α-MSH and ir ACTH from goldfish ( Carassius auratus) melanotropes was investigated using superfused isolated dispersed neurointermediate lobe cell columns. Stimulation of neurointermediate lobe cell columns with pulses of TRH evoked dose-dependent increases in the concomitant release of ir α-MSH and ir ACTH. Reversed-phase high performance liquid chromatography (RP-HPLC) was used to characterize the α-MSH and ACTH immunoreactivities released from a neurointermediate cell column under spontaneous release conditions. Six peaks of ir α-MSH were revealed. Three of these peaks were identified as des-acetyl α-MSH, mono-acetyl α-MSH and di-acetyl α-MSH. Seven peaks of ir ACTH were revealed. Four of these peaks were tentatively identified as ACTH variants. These studies suggest that TRH stimulates the release of peptide hormones from teleost melanotropes and that the goldfish neurointermediate lobe in vitro releases numerous peptides derived from POMC.