AJP - Regulatory, Integrative and Comparative Physiology, Vol 267, Issue 6 1437-R1444, Copyright © 1994 by American Physiological Society
Localization and analysis of natriuretic peptide receptors in the gills of the toadfish, Opsanus beta (teleostei)
J. A. Donald, T. Toop and D. H. Evans
Department of Zoology, University of Florida, Gainesville 32611.
The distribution and nature of natriuretic peptide binding sites was
determined in the gills of the toadfish, Opsanus beta. Specific
125I-labeled rat atrial natriuretic peptide (rANP) and 125I-labeled porcine
C-type natriuretic peptide (pCNP) binding sites were observed on the
afferent and efferent filamental arteries and lamellar arterioles, and on
the marginal channels of the secondary lamellae. In both section
autoradiography and competition assays, the binding of both ligands was
completely displaced by 1 microM rANP and 1 microM pCNP, but residual
binding was observed with 1 microM of the type C natriuretic peptide
receptor (NPR-C)-specific ligand C-ANF. Electrophoresis of gill membranes
cross-linked with 125I-rANP showed a major band at 75 kDa and a fainter
band at 140 kDa. Both rANP and pCNP significantly stimulated the production
of cGMP above basal levels; C-ANF had no stimulatory effect. These data
show that the intrafilamental gill vasculature of toadfish contains a major
population of natriuretic peptide receptors very similar to mammalian
clearance receptors and a smaller population of receptors that are linked
to a membrane-bound guanylate cyclase.
