Stretch-induced atriopeptin secretion in the isolated rat myocyte and its negative modulation by calcium.

Greenwald, James E.; Apkon, Michael; Hruska, Keith A.; Needleman, Philip

doi:10.1172/jci113948

Cited by 75 publications

(27 citation statements)

References 33 publications

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“…Secondly, we demonstrated that 46 nm TPA, known at these concentrations (10-100nM) to activate protein kinase C in this experimental model (Yuan et al, 1987), caused a slowly developing increase in the IR-ANP release from ventricular tissue. A similar pattern of ANP release with respect to levels and time course has been observed before, when intact rat hearts (without atrialectomy) were perfused under these experimental conditions (Ruskoaho et al, 1985; Greenwald et al (1989) reported that KCl produced a dosedependent release of ANP from suspensions of neonatal rat ventricular cells in culture and suggested that, like the atrial myocyte, the ventricular myocyte possesses the cellular mechanism(s) necessary to secrete ANP by a regulated pathway. In contrast, Bloch et al (1988) reported that shortterm exposure to the Na+-K+-adenosine-triphosphatase inhibitor, ouabain, stimulates the secretion of IR-ANP from atrial, but not from ventricular, cardiomyocytes in culture.…”

Section: Discussionsupporting

confidence: 78%

Effect of phorbol ester on the release of atrial natriuretic peptide from the hypertrophied rat myocardium

Kinnunen¹,

Taskinen²,

Järvinen³

et al. 1991

British J Pharmacology

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1 To determine the cellular mechanisms of atrial natriuretic peptide (ANP) release from ventricular cardiomyocytes, the secretory and the cardiac effects of a phorbol ester, 12-0-tetradecanoyl-phorbol-13-acetate (TPA), known to stimulate protein kinase C activity in heart cells, were studied in isolated, perfused heart preparations from 2-and 21-month-old Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. TPA was added to the perfusion fluid for 30 min at a concentration of 46 nm after removal of atrial tissue. Additionally, atrial and ventricular levels of immunoreactive ANP (IR-ANP) and ANP mRNA, the distribution of ANP within ventricles as well as the relative contribution of atria and ventricles in the release of ANP were studied. 2 Ventricular hypertrophy that gradually developed in hypertensive rats resulted in remarkable augmentation of ANP gene expression, as reflected by elevated levels of immunoreactive ANP and ANP mRNA. The total amount of IR-ANP in the ventricles of the SHR rats increased 41 fold and ANP mRNA levels 12.9 fold from the age of 2 to 21 months. At the age of 21 months, levels of IR-ANP and ANP mRNA in the ventricles of SHR rats were 5.4 fold and 3.7 fold higher, respectively, than in the normotensive WKY rats. Immunohistochemical studies demonstrated ANP granules within the hypertrophic ventricles of the old SHR rats, but not within normal ventricular tissue. 3 In isolated perfused heart preparations, the severely hypertrophied ventricular tissue of SHR rats after atrialectomy secreted more ANP into the perfusate than did the control hearts. The phorbol ester TPA caused a marked vasoconstriction in both the 2-month and 21-month old normal and hypertrophied hearts. Interestingly, the ANP release from the hypertrophied ventricles of the old SHR rats increased considerably (from 413 + 30 to the maximum of 623 + 75 pgml-1, F = 10.8, P < 0.001, two-way analysis of variance), whereas only a small increase was seen in old WKY rats and no effect was observed in young animals of either strain. When intact rat hearts (without atrialectomy) were used, infusion of phorbol ester also increased the ANP secretion into the perfusate in young animals. 4 Our present results indicate that the phorbol ester TPA increases the release of ANP from the hypertrophied, but not from normal rat myocardium. Thus, hypertrophied rat ventricular myocytes appear to possess the cellular mechanisms necessary to secrete ANP by a regulated pathway. The results further suggest that protein kinase C activity may be involved in the the regulation of ANP secretion from ventricular cells, as has been shown earlier for atrial myocytes.

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Section: Discussionsupporting

confidence: 78%

Effect of phorbol ester on the release of atrial natriuretic peptide from the hypertrophied rat myocardium

Kinnunen¹,

Taskinen²,

Järvinen³

et al. 1991

British J Pharmacology

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“…3 A and B); furthermore, AP-126 is only 50% cross-reactive with AP-28 with this antibody employed in the immunoassay. We observed that hypotonic stretch of cultured atrial myocytes induced the release of APir, which was enhanced (10-to 13-fold) when the cells were incubated in calcium-depleted medium containing EGTA or when the cells were pretreated with the intracellular calcium antagonist, 1, 2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid (6).…”

Section: Discussionmentioning

confidence: 95%

“…In contrast, the prohormone atriopeptin (AP)-126 [atrial natriuretic factor (ANF)- ] is stored in the atrial granules as the unprocessed prohormone (4). Cultured fetal or neonatal atrial myocytes release intact prohormone into the incubation medium in both the basal state (5) and when stimulated by stretch with hypotonic medium (6). On the other hand, isolated perfused rat or rabbit hearts only release mature hormone, AP-28 [ANF-(99-126)] (7)(8)(9).…”

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confidence: 99%

Manipulation of stretch-induced atriopeptin prohormone release and processing in the perfused rat heart.

Itō

Toki

Siegel

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

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Atriopeptin (AP) is stored as the prohormone AP-126 [atrial natriuretic factor-(1-126)] in atrial granules.Cultured atrial myocytes synthesize and release only prohormone into the medium. HPLC analysis of the coronary venous effluent of media from perfused rat hearts subjected to right atrial stretch indicated the presence of the C-terminal mature hormone AP-28 [atrial natriuretic factor-(99-126)] and little or no prohormone. Absence of calcium from the perfusion medium increased total AP release and surprisingly blocked the proteolytic cleavage of the prohormone. Similarly, addition of the proteolytic inhibitor aprotinin to the perfusion medium suppressed the processing of the endogenous AP-126 released by atrial stretch. Aprotinin would be restricted to the extracellular space, which is therefore implicated as the site of prohormone processing. This suggestion was validated by the demonstration that the perfused rat heart could readily cleave exogenous prohormone to mature hormone, a process blocked by aprotinin. Hypothetically, the stimulus-release-processing event initiated by atrial stretch may require the concerted action of the synthetic cell (i.e., atrial myocyte) and a processing cell or site (e.g., the adjacent atrial mesenchymal cell) for the production of the mature AP-28, which is the circulating molecular form of this endocrine system.The prohormone form of secreted proteins (e.g., proinsulin, preopiomelanocortin, and proenkephalin) are proteolytically cleaved to the mature hormone during vesicular packaging (1-3). Subsequent stimulation-secretion-coupling results in the release ofmature hormone during exocytosis. In contrast, the prohormone atriopeptin (AP)-126 [atrial natriuretic factor (ANF)-(1-126)] is stored in the atrial granules as the unprocessed prohormone (4). Cultured fetal or neonatal atrial myocytes release intact prohormone into the incubation medium in both the basal state (5) (15,16), but the cardiac cellular and subcellular localization of these enzymes has not been resolved. The inability of the cultured atrial myocyte to cleave the prohormone either suggests that the cell source is not necessarily the processing site or that the isolation or culturing conditions inactivate the cleavage enzyme.In the present study, we studied AP prohormone processing in the isolated, perfused rat heart, thereby precluding (i) the necessity to use enzymes (which could alter processing) in the isolation of cell types as in tissue culture experiments and (ii) the noncardiac processing that might occur in vivo in plasma or other tissues. MATERIALS AND METHODSMaterials. AP-126-Arg-Arg (11), representing amino acid residues 25-152 of the rat preprohormone coding sequence (17), was produced in Escherichia coli by using recombinant DNA techniques. The amino acid sequence was confirmed by gas-phase sequence analysis. AP-126-Arg-Arg was chosen as an exogenous prohormone substrate for the proteolytic processing experiments because it contained the complete amino acid sequence for the cleavage site be...

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“…It has been demonstrated that increased atrial stretch caused by increasing intravascular and atrial volume results in the secretion of ANP in several animal and human models (23,24). Increasing cell volume with hypoosmolar solutions results in cellular distension (stretch) and has recently been shown to increase ANP secretion from isolated atrial and ventricular myocytes (20). Our results indicate that over a wide range of osmolalities, both hypo-and hypertonic to the usual incubation medium, ANP secretion from diencephalic neurons in vitro is unaffected.…”

Section: Discussionmentioning

confidence: 99%

Atrial Natriuretic Peptide Secretion from Fetal Rat Diencephalon in Culture

Levin

Loughlin

Kaplan

1990

J Neuroendocrinology

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The presence of a distinct brain pool of the atrial natriuretic peptides (ANP) has been established. To determine the molecular forms and regulation of secretion of ANP, we studied fetal rat diencephalic neurons and glia in primary culture. ANP immunoreactivity determined by radioimmunoassay was found only in the neuron predominant cultures. The neurons contained mainly ANP (103-126) and less ANP (102-126), but secreted only ANP (103-126) into the medium after potassium and glutamate-dependent depolarization. Little, if any, ANP (99-126), the predominant form which circulates in plasma and originates from the heart, was secreted. The ability of potassium and glutamate to cause a mean 50% increase of ANP secretion above baseline was abolished after deleting calcium chloride from the medium. In contrast, hypo-or hyperosmolarity or increased sodium content in the incubation medium did not influence ANP secretion. These studies indicate that regulative secretion of ANP occurs from primary cultures of predominantly diencephalic neurons, probably accounting for the high concentrations of these peptides in this a r e a of the brain. The forms of ANP contained within the cells and secreted after depolarization are different from ANP secreted from neonatal rat atrial myocytes. In contrast to myocytes, varying sodium or osmolarity did not cause ANP secretion. We postulate that influences on ANP productionlsecretion in the brain may be distinct from the heart. Several polypeptide hormones with natriuretic and diuretic properties have now been isolated, purified and sequenced. The early members of the first hormone family with these properties were isolated from rat atrium and termed the atrial natriuretic peptides (ANP) (I). Subsequent characterization of the various precursor and circulating plasma forms shows that a 28 aminoacid peptide, ANP (99-126) is the predominant circulating hormone, though truncated forms and a 126 amino-acid prohormone can be detected in the plasma and in heart homogenates (2-4). Extensive peptide mapping studies have revealed both ANP immunoreactivity and mRNA coding for the hormone in other parts of the body, including the brain (5, 6). The greatest concentrations of mRNA for this peptide within the brain are found in the hypothalamic area (9, and the highest concentrations of A N P immunoreactivity are measured in parts of the anteroventral third ventricular area (7); the latter also contains a high density of ANP receptors (8). Possible functions for brain ANP include blood pressure regulation (9), cerebrospinal fluid production (10) and modulation of the secretion or action of pituitary hormones (1 1 -13): several of these functions are probably mediated through the diencephalon.By immunocytochemistry, ANP has been detected in the neurons of several brain nuclei, predominantly within the anteroventral third ventricular area (7). It is not established, however, that the neurons are capable of producing or secreting ANP; that is the immunoreactivity might represent receptor-mediated u...

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Stretch-induced atriopeptin secretion in the isolated rat myocyte and its negative modulation by calcium.

Cited by 75 publications

References 33 publications

Effect of phorbol ester on the release of atrial natriuretic peptide from the hypertrophied rat myocardium

Effect of phorbol ester on the release of atrial natriuretic peptide from the hypertrophied rat myocardium

Manipulation of stretch-induced atriopeptin prohormone release and processing in the perfused rat heart.

Atrial Natriuretic Peptide Secretion from Fetal Rat Diencephalon in Culture

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