Noradrenaline modulates hemocyte reactive oxygen species production via beta-adrenergic receptors in the oyster Crassostrea gigas

Catccholamines (CA) are known to be present in the microenvironment of moll uscan immunocytes. In the present study, experiments were conducted to dete rmine the effects of noradrenaline (NA), the principal CA circulating in bi valve hemolymph, on the luminol-dependent chemiluminescence (CL) of oyster Crassostrea gigas hemocytes. Results show that NA had a dose-dependent inhi bitory effect on the CL-response at the physiological concentration of 0.1 muM and above. The alpha -adrenoceptor agonist phenylephrine had no signifi cant effect on the CL-response whereas the beta -adrenoceptor agonist isopr oterenol mimicked the inhibitory effects of NA on the CL-response. The beta -adrenoceptor antagonist propanolol, but not the alpha -adrenoceptor antag onist prazosin, prevented the negative effects of NA on the CL-response. Ta ken together, these results show that beta -adrenergic receptors are presen t at the surface of oyster hemocytes and allow NA to down-regulate the CL-r esponse. (C) 2001 Elsevier Science Ltd. All rights reserved.