Natriuretic peptide guanylyl cyclase receptors in the kidney of the Japanese eel, Anguilla japonica

Abstract

Natriuretic peptides are linked to osmoregulation, cardiovascular and volume regulation in fishes. The peptides bind to two guanylyl-cyclase-linked receptors, natriuretic peptide receptor-A (NPR-A) and NPR-B, to elicit their effects. Atrial natriuretic peptide (ANP) binds principally to NPR-A, whereas C-type natriuretic peptide (CNP) binds to NPR-B. The teleost kidney has an important role in the maintenance of fluid and electrolyte balance; therefore, the location of NPR-A and NPR-B in the kidney could provide insights into the functions of natriuretic peptides. This study used homologous, affinity purified, polyclonal antibodies to NPR-A and NPR-B to determine their location in the kidney of the Japanese eel, Anguilla japonica. Kidneys from freshwater and seawater acclimated animals were fixed overnight in 4% paraformaldehyde before being paraffin-embedded and immunostained. NPR-A immunoreactivity was found on the apical membrane of proximal tubule 1 and the vascular endothelium including the glomerular capillaries. In contrast, NPR-B immunoreactivity was located on the smooth muscle of blood vessels including the glomerular afferent and efferent arterioles, and on smooth muscle tissue surrounding the collecting ducts. No difference in the distribution of NPR-A and NPR-B was observed between freshwater and seawater kidneys. Immunoreactivity was not observed in any tissue in which the antibodies had been preabsorbed. In addition, there was no difference in NPR-A and NPR-B mRNA expression between freshwater-acclimated and seawater-acclimated eels. These results suggest that, although utilizing the same second messenger system, ANP and CNP act on different targets within the kidney and presumably elicit different effects.

Area postrema, a brain circumventricular organ, is the site of antidipsogenic action of circulating atrial natriuretic peptide in eels

“…Specificity of immunoreactive signals was confirmed by preabsorption of the antibody with antigenconjugated CNBr-activated Sepharose 4B (GE Healthcare, Bucks, UK). The specificity of this antiserum in eel tissue was confirmed by western blotting of membrane fractions prepared from the gills as previously reported (Healy et al, 2005). Immunostained sections were counterstained with Haematoxylin and then dehydrated and cleared, and coverslips placed on top for observation with a light microscope (E800, Nikon, Tokyo, Japan).…”

Modulation by Brain Natriuretic Peptide of GABA Receptors on Rat Retinal ON-Type Bipolar Cells

“…As shown in Figure 1 A, in addition to a band at ϳ125 kDa, corresponding to the size of the native rat NPR-A (Lowe and Fendly, 1992;Healy et al, 2005), the antibody to NPR-A revealed an additional band at ϳ180 kDa, which might be attributable to glycosylation of the protein, consistent with previous work (Healy et al, 2005). The antibody to NPR-B revealed a single band at the corresponding molecular weight (130 kDa) (Healy et al, 2005). Figure 1, B and BЈ, shows the confocal laser microphotographs of the vertical sections of rat retinas, immunolabeled by the anti-NPR-A and anti-NPR-B antibodies, respectively.…”

Inhibitory effect of dendroaspis natriuretic peptide on spontaneous contraction in gastric antral circular smooth muscles of guinea pigs

“…The NPR was extensively distributed in many tissues and systems; for example, in the rat brain [18] , in the kidney of the Japanese eel (Anguilla japonica) [19] , in the guinea pig cecum [20] , and in the rat heart [21] . In the present study, we found that the NPR also exists in the stomach of guinea pigs and the density is largest in the gastric antrum.…”