Identification and characterization of adenosine 5'-tetraphosphate in human myocardial tissue.
Endocrine functions of the human heart have been studied extensively. Only recently, nucleotidergic mechanisms have been studied in detail. Therefore, an isolation strategy was developed to isolate novel nucleotide compounds from human myocardium. The human myocardial tissue was fractionated by several chromatographic studies. A substance purified to homogeneity was identified as adenosine 5'-tetraphosphate (Ap(4)) by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS), post-source decay MALDI MS, and enzymatic cleavage analysis. Furthermore, Ap(4) was also identified in ventricular specific granules. In the isolated perfused rat heart, Ap(4) elicited dose-dependent vasodilations. Vasodilator responses were abolished in the presence of the P(2Y1) receptor antagonist MRS 2179 (1 microm) or the NO synthase inhibitor N(G)-nitro-l-arginine methyl ester (50 microm). After removal of the endothelium by Triton X-100, Ap(4) induced dose-dependent vasoconstrictions. Inhibition of P(2X) receptors by pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (30 microm) or desensitization of P(2X) receptors by alpha,beta-methylene ATP (alpha,beta-meATP, 1 microm) diminished these vasoconstrictor responses completely. In the present study Ap(4) has been isolated from human tissue. Ap(4) was shown to exist in human myocardial tissue and was identified in ventricular specific granules. In coronary vasculature the nucleotide exerted vasodilation via endothelial P(2Y1) receptors and vasoconstriction via P(2X) receptors on vascular smooth muscle cells. Ap(4) acts as an endogenous extracellular mediator and might contribute to the regulation of coronary perfusion.
Westhoff
Timm
T
Freie Universität Berlin, Universitätsklinikum Benjamin Franklin, Medizinische Klinik IV, Hindenburgdamm 30, 12200 Berlin, Germany.
Jankowski
Joachim
J
Schmidt
Sven
S
Luo
Jiankai
J
Giebing
Günter
G
Schlüter
Hartmut
H
Tepel
Martin
M
Zidek
Walter
W
van der Giet
Markus
M
D000227:Adenine Nucleotides / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D003902:Detergents / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000473:pathology; D006801:Humans; D008297:Male; D009206:Myocardium / Q000378:metabolism* / Q000473:pathology; D017830:Octoxynol / Q000494:pharmacology; D010477:Perfusion; D051381:Rats; D011921:Rats, Inbred WKY; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013552:Swine; D013997:Time Factors; D014466:Ultraviolet Rays; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D000227:Adenine Nucleotides; D003902:Detergents; D014662:Vasoconstrictor Agents; C017991:adenosine 5'-tetraphosphate; D017830:Octoxynol