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  • sarcoplasmic reticulum  (3)
  • ACE inhibition  (2)
  • 1995-1999  (4)
  • 1990-1994  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 359 (1999), S. 394-399 
    ISSN: 1432-1912
    Keywords: Key words Angiotensin II ; ACE inhibition ; Moexiprilat ; Enalaprilat ; Cardiac fibroblast ; Mitogen ; activated protein kinases (MAPKs) ; Signal transducer and activator of transcription (STAT)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied the effects of angiotensin converting enzyme (ACE) inhibitors on angiotensin II (Ang II) induced growth related signalling pathways in neonatal rat cardiac fibroblasts. In BrdU proliferation assays, Ang II (10–9–10–7 M) stimulated cardiac fibroblast growth in a dose-dependent fashion (maximum at 10–7 M, 5.22 ± 0.01-fold, n = 9). 2-2-(1-(ethoxycarbonyl)-3-phenylpropyl)-[amino-oxopropyl]-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline-3 carboxylic acid (moexiprilat) led to a dose-dependent inhibition of the Ang II induced cardiac fibroblast growth. A less pronounced effect on cellular proliferation was seen with the ACE inhibitor enalaprilat. To elucidate the mechanisms involved in this direct antiproliferative effect of ACE inhibitors in cardiac fibroblasts, we studied the activation of mitogen-activated protein kinases [MAPKs: extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38-MAPK] and JAK/STAT (janus kinases/signal transducer and activator of transcription) signal transduction pathways. Ang II (10–7 M) caused an increase in MAPKs activity with an increased phosphorylation of ERK1/2 (1.7-fold) and p38-MAPK (3.6-fold). This effect was completely inhibited by moexiprilat (10–7 M) and enalaprilat (10–7 M). Stimulation with Ang II (10–7 M) also led to an increased phosphorylation of STAT3, which is one of the key effector proteins in the JAK/STAT signalling pathway. This effect was also completely inhibited by moexiprilat (10–7 M) and enalaprilat (10–7 M). These data show that the ACE inhibitors moexiprilat and enalaprilat inhibit Ang II induced proliferation of cardiac fibroblasts according to their relative potency of ACE inhibition in vitro. This novel effect of ACE inhibitors is accompanied by blocking the Ang II induced activation of several intracellular signal transduction pathways (ERK1/2, p38-MAPK and STAT3).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: Enalapril ; circadian pharmacokinetics ; ACE inhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Possible circadian changes in the pharmacokinetics and effect on serum angiotensin-converting enzyme (ACE) activity of the ACE inhibitor enalapril have been studied in 8 healthy subjects after oral ingestion of 10 mg enalapril maleate either at 08.00 h or 20.00 h. The time to peak serum concentration (tmax) of enalapril was increased after administration at 20.00 h compared to 08.00 h (2.4 h versus 1.3 h), where as other kinetic parameters were not significantly altered. The 24 h-kinetics of the active metabolite enalaprilat did not differ significantly between the two treatments, but the area under the curve (AUC (0–24)) and the peak serum concentration (Cmax) were slightly higher after intake at 20.00 h. The relationship between the measured serum enalaprilat level and the degree of inhibition of serum ACE was the same after both treatments. Overall, the evening and morning administration of enalapril did not differ markedly in the pharmacokinetics and the time course of ACE inhibition.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-4919
    Keywords: neonatal rat cardiomyocyte culture ; sarcoplasmic reticulum ; phospholamban ; calcium ATPase ; calcium transport ; thyroid hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This study investigates sarcoplasmic reticulum (SR) calcium-(Ca2+) transport ATPase (SERCA2a) and phospholamban (PLB) in cultured spontaneously contracting neonatal rat cardiomyocytes (CM) to ascertain the function of both SR proteins under various culture conditions. The two major SR proteins were readily detectable in cultured CM by immunofluorescent microscopy using specific anti-SERCA2 and anti-PLB antibodies. Double labeling technique revealed that PLB-positive CM also labeled with anti-SERCA2. Coexpression of SERCA2 and PLB in CM was supported by measurement of cell homogenate oxalate-supported Ca2+ uptake which was completely inhibited by thapsigargin and stimulated by protein kinase A-catalyzed phosphorylation. Under serum-free conditions, incubation of CM with the SERCA2a expression modulator 3,3′,5-triiodo-L-thyronine (100 nM, 72 h) resulted in elevated Ca2+ uptake of +33%. Specific Ca2+ uptake activity was not altered if insulin was omitted from the serum-free culture medium but total SR Ca2+ transport activity was reduced under this culture condition. The results indicate that primary culture of spontaneously contracting neonatal rat CM can be employed as a useful model system for investigating both short- and long-term mechanisms determining the Ca2+ re-uptake function of the SR under defined culture conditions.
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  • 4
    ISSN: 1573-4919
    Keywords: heart ; postnatal development ; sarcoplasmic reticulum ; phospholamban ; calcium transport ; spontaneously hypertensive rats ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This comparative study investigates the relationship between sarcoplasmic reticulum (SR) calcium(Ca2+)-ATPase transport activity and phospholamban (PLB) phosphorylation in whole cardiac homogenates of spo`ntaneously hypertensive rats (SHR) and their parent, normotensive Wistar Kyoto (WKY) strain during early postnatal development at days 1, 3, 6, 12 and at day 40 to ascertain any difference in SR Ca2+ handling before the onset of hypertension. At day 1, the rate of homogenate oxalate-supported Ca2+ uptake was significantly higher in SHR than in WKY (0.25 ± 0.02 vs 0.12 ± 0.01 nmoles Ca2+/mg wet ventricular weight/min, respectively; p 〈 0.001). This interstrain difference disappeared with further developmental increase in SR Ca2+ transport. Western Blot analysis and a semiquantitative ELISA did not reveal any difference in the amount of immunoreactive PLB (per mg of total tissue protein) between strains at any of the ages studied. In addition, levels of phosphorylated PLB formed in vitro in the presence of radiolabelled ATP and catalytic (C) subunit of protein kinase A did not differ between SHR and WKY at days 1, 3, 6 and 12. At day 40, C subunit-catalyzed formation of 32P-PLB was reduced by 66% (p 〈 0.001) in SHR when compared to age-matched WKY In the early postnatal period between day 1 and 12 SR Ca2+-transport values were linearly related to the respective 32P-PLB levels of both SHR and WKY rats. The results indicate that cardiac SR of SHR can sequester Ca2+ at a much higher rate immediately after birth compared to WKY rats. The disappearance of this interstrain difference with further development suggests that some endogenous neuroendocrine or nutritional factor(s) from the hypertensive mother may exert an influence upon the developing heart in utero resulting in a transiently advanced maturation of the SR Ca2+ transport function in SHR pups at the time of birth.
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  • 5
    ISSN: 1573-4919
    Keywords: atria ; thyroid hormones ; β-adrenergic effect ; sarcoplasmic reticulum ; phospholamban
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract This paper discusses the mechanisms of two basic effects of thyroid hormones on atrial responses to β-adrenergic agonists, i.e. increased inotropic sensitivity and decreased maximal contractile responsiveness. The increased sensitivity of atria to β-adrenergic agonists under thyroid hormones appears to be related to increases in β-adrenoceptor density and Gs/Gi protein ratio, leading to activation of Gs-mediated pathway, but suppression of Gi-mediated pathway of adenylate cyclase regulation. Therefore, the i/c concentrations of cAMP and corresponding inotropic responses achieve their maximums at lower doses of β-adrenergic agonist. Thyroid hormones also decrease the expression of phospholamban, but increase the expression of sarcoplasmic reticulum Ca+2-pump. As a result, the basal activity of sarcoplasmic reticulum Ca+2-pump increases, but its β-adrenergic activation through phosphorylation of phospholamban decreases. It is suggested that these changes are causal for decreased maximal inotropic and lusitropic responses of atria to β-adrenergic agonists.
    Type of Medium: Electronic Resource
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