Nitrite released in haemocytes from Mytilus galloprovincialis, Crassostreagigas and Ruditapes decussatus upon stimulation with phorbol myristate acetate

In order to demonstrate the involvement of nitric oxide in the defence syst ems of marine bivalves, we investigated the production of superoxide and ni trite, following in vitro phorbol myristate acetate stimulation of Mytilus galloprovincialis, Crassostrea gigas and Ruditapes decussatus haemocytes. W hereas M. galloprovincialis and C. gigas haemocytes were found to produce s uperoxide and nitrite, R. decussatus haemocytes were found to be unable to generate either of these mediators. Nitrite is a stable end product of nitr ic oxide and peroxynitrite as well; it appeared therefore that some marine bivalves, to kill microbial pathogens, use NADPH-oxidase and nitric oxide s ynthase pathways. This was confirmed at an experimental level where inhibit ors of both enzymatic pathways blocked the production of nitrite. Moreover, this notion was strengthened by the inability of the haemocytes from R. de cussatus, which cannot produce superoxide, to release nitrite when stimulat ed. (C) 2000 Ifremer/Cnrs/Inra/Ird/Cemagref/Editions scientifiques et medic ales Elsevier SAS.