PARTIAL-PURIFICATION, TISSUE DISTRIBUTION AND MODULATORY ACTIVITY OF A CRUSTACEAN CHOLECYSTOKININ-LIKE PEPTIDE

Reversed-phase chromatography was used to separate several forms of ch olecystokinin-like peptides (CCKLP) from the pericardial organs (PCOs) of the spiny lobster Panulirus interruptus. Fast protein liquid chrom atography of PCOs, stomatogastric ganglia (STGs) and eyestalks reveale d five peaks of CCKLP (peaks A-E) that were common to all three tissue s, as well as two additional peaks (peaks F acid G) in the STG. Peaks A-E were present in the hemolymph of fed, but not starved, lobsters. T he bioactivity of peaks A-E was tested on the gastric mill rhythm of t he isolated STG. Only peak E elicited activity. The effects of peak E included activating the gastric mill rhythm in quiescent preparations and strengthening existing rhythms in a dose-dependent manner. Further purification of peak E by high performance liquid chromatography reso lved this peak into two immunoreactive peaks, one of which retained it s bioactivity. The effects of peak E were blocked by the CCK antagonis t proglumide. These results are consistent with a role for peak E in t he feeding-induced activation of the gastric mill.