Involvement of crustacean hyperglycemic hormone in the control of gill iontransport in the crab Pachygrapsus marmoratus

Total extracts of sinus glands (SG) of the euryhaline grapsid crab Pachygra psus marmoratus contain peptidic factor(s) that stimulate osmoregulatory pr ocesses in isolated and perfused posterior gills from crabs acclimated to d ilute seawater. This study investigated the nature of the active factor(s). Separation of P. marmoratus SG peptides by reverse-phase HPLC, followed by a direct enzyme-linked immunosorbent assay using an anti-Carcinus maenas c rustacean hyperglycemic hormone (CHH) antiserum, identified a major immunor eactive chromatographic peak. A glucose quantification bioassay demonstrate d a strong and specific hyperglycemic activity following injection of the i mmunoreactive peak, therefore defined as the CHH of P. marmoratus. Isolated posterior gills were then perfused with HPLC fractions using a dose of 4 S G equivalents/assay. The CHH fraction consistently and significantly increa sed the transepithelial potential difference and Na+ influx by about 50%. T he effect was rapid and reversible. Another substance of unknown nature (el uted earlier than CHH in the HPLC gradient) caused a small increase in Nainflux (14%) but had no effect on the transepithelial potential difference. No other peptidic product from the SG had significant effect on the measur ed osmoregulatory parameters. These results indicate that CHI-I, in additio n to its hyperglycemic activity, is also implicated in the control of branc hial ionic transport. This neuropeptide may thus constitute a major factor involved in the control of osmoregulation in decapod crustaceans. (C) 2000 Academic Press.