Meeting Abstract

81.4  Tuesday, Jan. 6  Co-localization of the specific binding sites of crustacean hyperglycemic hormones (CHHs) of eyestalk and pericardial organ on multiple tissues of the blue crab, Callinectes sapidus KATAYAMA, Hidekazu; CHUNG, J. Sook*; University of Maryland Biotechnology Institute, Baltimore chung@comb.umbi.umd.edu

Despite a large number of isoforms of hyperglycemic hormone (CHH) have been structurally characterized from many crustacean species, their physiological functions of those particularly found in non-eyestalk tissues are not clearly demonstrated. In the search of target tissue(s) of the pericardial organ crustacean hyperglycemic hormone (PO-CHH), we employed a second messenger assay and a radiolabeled ligand receptor binding assay to locate putative target tissues, along with eyestalk-CHH (ES-CHH). The membranes were prepared from various tissues of Callinectes sapidus: hepatopancreas, hindgut, midgut, gills, heart, abdominal muscles, and scaphognathites. Like ES-CHH, PO-CHH showed multiple target tissues and specifically bound membranes of scaphognathites = abdominal muscles > midgut > gills > heart > hindgut and hepatopancreas (listing order corresponds with the number of binding sites). The specific binding sites of [125I] ES-CHH in hepatopancreas and gills were saturable and displaceable. The binding sites of abdominal muscles membrane were specific and saturable, but appeared to be promiscuous by binding to both CHHs, while they showed differences in displacement. The results obtained from the binding study suggest that PO-CHH also has multiple target tissues in which abdominal muscles and scaphognathites are the primary tissues. As for the second messenger, we observed the difference in the amount of cGMP production by ES-and PO-CHHs in these tissues. The differences in the primary amino acid sequences of ES- and PO-CHH, may be responsible for the truncated responses of hyperglycemia, cGMP stimulation, and binding affinity.