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  • 1
    ISSN: 1432-1912
    Keywords: Key words Nociceptin ; [Phe1Ψ(CH2-NH)Gly2]NC(1 ; 13)NH2 ; Rat and mouse vas deferens ; Guinea pig ileum and renal pelvis ; Blood pressure ; Heart rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Nociceptin (NC), a series of NC fragments, naloxone as well as the pseudopeptide [Phe1Ψ(CH2-NH)Gly2]NC(1–13)NH2 ([F/G]NC(1–13)NH2) were used to characterize NC receptors in peripheral isolated organs and in vivo. Experiments on isolated organs were performed in the mouse (mVD) and rat (rVD) vas deferens (noradrenergic nerve terminals), in the guinea pig ileum (gpI; cholinergic nerves) and in the renal pelvis (gpRP; sensory nerves), and, in vivo, by measuring the blood pressure (BP) and heart rate (HR) in anaesthetised rats. NC, NCNH2 and NC(1–13)NH2 acted as full agonists with similar affinities, while shorter fragments (e.g. NC(1–12)NH2, NC(1–9)NH2, NC(1–5)NH2) were much weaker or inactive. The inhibitory effects of NC were not modified by naloxone. [F/G]NC(1–13)NH2 acted as an antagonist with similar pA 2-values (6.75 mVD, 6.83 rVD, 7.26 gpI) in the three species. In addition, it blocked NC actions in the rat in vivo. Linear Schild plots with slopes near to unity indicated that [F/G]NC(1–13)NH2 is a competitive antagonist, specific for NC receptors both in vitro (since it was inactive on opioid receptors) and in vivo (since it was inactive against carbachol). [F/G]NC(1–13)NH2 showed a residual agonistic activity in vitro (α = 0.2-0.3 in the rVD and gpI) and especially in vivo (α = 0.4 BP, 0.2 HR). These pharmacological data indicate that NC and related peptides exert their inhibitory effects in peripheral organs of various species by activating the same receptor type. Moreover, [F/G]NC(1–13)NH2 appears to be a useful tool for receptor characterization and classification.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1619-7089
    Keywords: Atrial natriuretic peptide ; Atrial natriuretic factor ; Radioiodinated peptides ; High-performance liquid chromatography ; Kinetic study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In the present paper we evaluate the optimum chemical conditions for labelling atrial natriuretic peptide (ANP) and its metabolites and for preparing highly purified radiotracers which can be used for in vivo kinetic studies of ANP in humans. Synthetic a h1–28ANP and some hormone metabolites were iodinated with Na125I or Na131I by means of the lactoperoxidase (ANP) or the chloramine-T (ANP metabolites) technique. The biological activity of labelled ANP was tested by means of a binding study using mouse cardiac membranes. A high-performance liquid chromatography (HPLC) procedure was used to purify the labelled hormone and the principal labelled metabolites in venous plasma samples collected up to 50 min after the injection of125I-labelled ANP from nine healthy men. The main ANP kinetic parameters were derived from the disappearance curves of the [125I]ANP, which were satisfactorily fitted by a biexponential function in all subjects. The main advantages of this tracer technique are: (1) high accuracy, allowing the identification of the metabolites produced in vivo under steady-state conditions after injection of the precursor (labelled hormone); (2) high sensitivity, allowing the detection of minimal quantities of metabolites (that cannot be identified on the basis of the integrated areas from the ultraviolet-absorbing peaks on HPLC); (3) high specificity, allowing the detection of possible in vitro artefactual generation of cleavage products of ANP using an internal labelled standard. Utilizing this tracer method, it was possible to estimate the principal parameters of ANP kinetics and also to plot the appearance curves of the labelled metabolites produced in vivo after the injection of the labelled precursor.
    Type of Medium: Electronic Resource
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