C‐type natriuretic peptide stimulates secretion of growth hormone from rat‐pituitary‐derived GH3 cells via a cyclic‐GMP‐mediated pathway

Abstract

Although C-type natriuretic peptide (CNP) has been shown to exist at the highest concentration in the anterior pituitary in rat tissues, its physiological role(s) there is (are) not clear. In this study, we report a novel function of CNP examined with anterior pituitary-derived cell lines, GH3 and AtT20/D16v-F2. Both CNP and atrial natriuretic peptide (ANP) increased cellular cGMP levels in both cell lines in dose-dependent manners. CNP, but not ANP, stimulated growth hormone (GH) release from GH3 cells. In contrast, neither ANP nor CNP had any significant effect on the corticotropin release from AtT20/D16v-F2 cells. An activator for cGMP-dependent protein kinase (cGK), dibutyryl cGMP, mimicked the stimulation of GH release from GH3 cells by CNP. Constitutive GH release from GH3 cells was greatly diminished in the presence of inhibitors for CAMP-dependent protein kinase, while stimulative GH release by CNP was not affected. However, inhibitors which can block cGK almost completely diminished the stimulative effect of CNP. An inhibitor for protein kinase C did not show any effect on either constitutive or CNP-stimulative GH release. Our observations indicate that the stimulation of GH release from GH3 cells by CNP is mediated mainly by the cGK signal-transduction pathway, not by CAMP-dependent protein kinase or protein kinase C, through a CNP-specific receptor (possibly ANP-B receptor). Thus, CNP may act as a local modulator in the anterior pituitary.C-type natriuretic peptide (CNP) is the third member of the mammalian natriuretic peptide family discovered following atrial natriuretic peptide (ANP) [l] and brain natriuretic peptide (BNP) [2]. CNP was first isolated from porcine brain [3, 41, then identified in rat and human brains [5, 61. CNP possesses sequence similarity to ANP and BNP. According to the cloned cDNA and genes for CNP from various species [5-91, its structure is highly conserved among species and, actually, rat, porcine and human CNP-22, the smaller molecular form with 22 amino acid residues, are identical. CNP has been shown to exert pharmacological actions similar to ANP and BNP, for example, natriuretic, diuretic and vasorelaxant effects [lo, l l ] , albeit with a lesser Correspondence to K. Nagata, Shionogi Research Laboratories, Shionogi & Co., Ltd., 5-12-4 Sagisu, Fukushima-ku, Osaka, Japan 553Abbreviations. CNP, C-type natriuretic peptide ; ANP, atrial natriuretic peptide; BNP, brain natriuretic peptide; GH, growth hormone ; ACTH, corticotropin ; PRL, prolactin ; cGK, cGMP-dependent protein kinase; cAK, CAMP-dependent protein kinase ; PKC, protein kinase C ; db-CAMP, N6,2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (sodium salt) ; db-cGMP, iV,2'-O-dibutyrylguanosine 3':5'-cyclic monophosphate (sodium salt); H-85, N-[2-(N-formyl-p-chlorocinnamylamino)ethyl]-5-isoquinolinesulfona~de; H-88, N-(2-cinnamylaminoethyl)-5-isoquinolinesulfonamide ; H-89, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide; KT-5720, (SR, 9S, 11S)-( -)-9-hydroxy-9-hexyloxycarbonyl-8-methy1-2,3,9,10-tetrah...

Expression of guanylyl cyclase-B (GC-B/NPR2) receptors in normal human fetal pituitaries and human pituitary adenomas implicates a role for C-type natriuretic peptide

“…Our demonstration that pituitary tumor tissue also expresses NPR2/GC-B raises the intriguing possibility that these receptors might be useful in generating novel therapies, although pituitary adenomas are usually slow growing and rarely malignant (Melmed 2003). It remains to be established whether GC-B receptors in human pituitary tissue can act as secretagogue modulators, although previous studies suggest that both CNP and NO are capable of stimulating GH secretion from rodent pituitaries (Shimekake et al 1994), human fetal pituitaries, and human pituitary adenomas (Rubinek et al 2005).…”

Molecular characterisation and functional interrogation of a local natriuretic peptide system in rodent pituitaries, αT3-1 and LβT2 gonadotroph cells

“…A few studies report effects of natriuretic peptides on the secretion of GH and ACTH in vitro (Gilkes et al 1994, Shimekake et al 1994, Guild & Cramb 1999, and soluble guanylyl cyclase activity has been implicated in regulating gonadotrophin secretion (Ceccatelli et al 1993). To examine the potential effects of ANP and CNP on LH secretion, we cultured freshly dispersed primary male rat anterior pituitary cells under two experimental paradigms; static culture in 24-well plates and under superfusion conditions following culture on cytodex beads.…”

C-type natriuretic peptide (CNP) effects in anterior pituitary cell lines: evidence for homologous desensitisation of CNP-stimulated cGMP accumulation in alpha T3-1 gonadotroph-derived cells

“…However, there is conflicting evidence, based on a number of studies, as to which natriuretic peptide GC receptor is predominant in anterior pituitary cells, due mostly to the diverse range of techniques utilised (Kurihara et al 1987, Koch et al 1988, Wilcox et al 1991, Konrad et al 1992, Tallerico-Melnyk et al 1992, McArdle et al 1993,b, Gilkes et al 1994a, Shimekake et al 1994, Grandclément et al 1995, Langub et al 1995, Guild & Cramb 1999.…”