C-type natriuretic peptide receptors and signaling in rectal gland of Squalus acanthias

Abstract

Recent evidence suggests that the newly described natriuretic peptide, C-type natriuretic peptide (CNP), may be the circulating form of natriuretic peptide in the shark. In the shark CNP has a major site of action in the rectal gland, which augments chloride secretion in response to stimulation by volume loading or CNP infusion. We therefore examined the shark rectal gland for natriuretic peptide receptors and determined the presence of guanylate cyclase-linked receptors and non-guanylate cyclase-linked receptors for CNP in this tissue. CNP binds with uniform high affinity (dissociation constant of 78 +/- 11 pM) to receptors of high density (receptor density of 61 +/- 0.7 fmol/mg protein) in plasma membranes prepared from the rectal gland. By use of rat atrial natriuretic peptide (rANP) as a competing ligand, two classes of receptors become apparent in this population, both of which have similar affinity for CNP, but different affinities for rANP. The low-molecular-weight natriuretic peptide receptor-specific peptide, des-[Gln116,Ser117,Gly118, Leu119,Gly120]rANP-(102-121), binds to 50% of the receptors in the rectal gland, but fails to bind to the remaining 50% even at micromolar concentrations. Porcine brain natriuretic peptide (pBNP) binds with uniformly diminished affinity to all receptors, whereas the unrelated peptide, porcine vasoactive intestinal peptide, does not bind these receptors. The importance of the integrity of the ring structure of CNP is underlined by the significant loss of affinity when the peptide ring is opened.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of goby posterior intestinal NaCl absorption by natriuretic peptides and by cardiac extracts

“…Consistent with the role of NP in hydromineral homeostasis, the list of ion-transporting epithelial targets for NP is extensive and in fishes includes the intestine, renal tubule, elasmobranch rectal gland, and teleost opercular membrane (O'Grady et al, 1985;Lee and Malvin 1987;Westenfelder et at. 1988;O'Grady 1989;Evans 1990;Ando et al 1992;Gunning et al 1993;Takei and Balment 1993;Loretz 1993Loretz , 1994Loretz , 1995aTakei 1994). In his review of the role of NP in the osmoregulation of fishes, Evans (1990) considered dual actions for NP including regulation of membrane ion transport processes and also hemodynamic effects, particularly vasodilation, which might indirectly modify ion transport by increasing blood flow to osmoregulatory organs.…”

Biophysiology of natriuretic peptides in the evolutionary varieties of vertebrate osmoregulatory systems from shark rectal to mammalian salivary glands

“…GCT cells of the murine and rat submandibular salivary glands synthesize many growth factors, including EGF and NGF (34,(82)(83)(84)(85). Striated ducts in human salivary glands also express many types of growth factor in addition to NP families.…”

“…CNP in the shark heart stimulates chloride secretion by the rectal gland, suggesting that CNP receptors are present in the rectal gland. Gunning et al concluded that the shark rectal glands expressed two populations of receptors for NPs, one that was linked to guanylate cyclase and another that resembled the low-molecular receptor for ANP (34). Elasmobranchs (sharks, skates, and rays) are hyperosmotic and hyponatremic relative to seawater, and at risk for both volume expansion and hypernatremia.…”

“…It has been reported that among various CNPs, the biologically active receptor for shark CNP (sCNP) in the rectal gland resembles the ANPR-B receptor. Shark CNP was found to be more potent than hANP, which was more potent than porcine BNP, while hANP had no effects (29)(30)(31)(32)(33)(34)(35). Rectal gland secretion in a glass chamber was analyzed for chloride concentration (36).…”

Characterisation of C-type natriuretic peptide receptors in the gill of dogfish Triakis scyllia

“…The presence of GC-coupled receptors found in the present study also suggests CNP action on the Triakis rectal gland. In the rectal gland of spiny dogfish, two types of receptor have been identified, GC-coupled and uncoupled receptors, using porcine CNP, Squalus CNP, rat ANP, porcine BNP and C-ANF (Gunning et al 1993). …”