IMMUNOLOCALIZATION OF AN ANTIGEN ASSOCIATED WITH THE INVERTEBRATE ELECTROGENIC 2NA(+) 1H(+) ANTIPORTER/

Epithelial plasma membranes from crustacean gut, kidney and gills have been shown recently to display an electrogenic 2Na(+)/1H(+) antiporte r Chat differs considerably in its physiological properties from the v ertebrate electroneutral 1Na(+)/1H(+) exchange paradigm. In this study , we describe the histological and cytological localization of an anti gen associated with invertebrate electrogenic 2Na(+)/1H(+) antiport in lobster (Homarus americanus) tissues using a monoclonal antibody (MAb 11) raised in mice against purified brush border membranes of the hep atopancreatic epithelium. Previous work showed that MAb 11 inhibited e lectrogenic 2Na(+)/1H(+) and Ca2+/H+ exchange by hepatopancreatic brus h border membrane vesicles, but was without effect on Na+-dependent D- glucose transport, suggesting a restricted inhibitory specificity to t he cation exchanger. MAb 11 binding occurred at hepatopancreatic epith elial R-cell brush border membranes, at plasma membranes of the antenn al gland and gill podocytes, and at vacuolar membranes of hepatopancre atic B- and R-cells, gill nephrocytes and epithelial cells of the ante nnal gland labyrinth and gill lamellae, as assessed by FITC-labelled s econdary antibodies. Control FITC-labelled antibodies raised in mice a gainst vertebrate keratin proteins displayed only weak non-specific bi nding to the tissues and cells responding intensely to MAb 11, support ing the specific nature of MAb 11 binding to its cognate antigen. The broad histological and cytological distribution of MAb 11 binding to p lasma membranes and vacuolar membranes from several lobster organ syst ems suggests that the physiological activities regulated by its antige n, possibly an element of the invertebrate electrogenic cation exchang er, may be diverse.