Production of NAADP and its role in Ca2+ mobilization associated with lysosomes in coronary arterial myocytes

Am J Physiol Heart Circ Physiol. 2006 Jul;291(1):H274-82. doi: 10.1152/ajpheart.01064.2005. Epub 2006 Feb 10.


The present study was designed to determine the production of nicotinic acid adenine dinucleotide phosphate (NAADP) and its role associated with lysosomes in mediating endothelin-1 (ET-1)-induced vasoconstriction in coronary arteries. HPLC assay showed that NAADP was produced in coronary arterial smooth muscle cells (CASMCs) via endogenous ADP-ribosyl cyclase. Fluorescence microscopic analysis of intracellular Ca2+ concentration ([Ca2+]i) in CASMCs revealed that exogenous 100 nM NAADP increased [Ca2+]i by 711 +/- 47 nM. Lipid bilayer experiments, however, demonstrated that NAADP did not directly activate ryanodine (Rya) receptor Ca2+ release channels on the sarcoplasmic reticulum. In CASMCs pretreated with 100 nM bafilomycin A1 (Baf), an inhibitor of lysosomal Ca2+ release and vacuolar proton pump function, NAADP-induced [Ca2+]i increase was significantly abolished. Moreover, ET-1 significantly increased NAADP formation in CASMCs and resulted in the rise of [Ca2+]i in these cells with a large increase in global Ca2+ level of 1,815 +/- 84 nM. Interestingly, before this large Ca2+ increase, a small Ca2+ spike with an increase in [Ca2+]i of 529 +/- 32 nM was observed. In the presence of Baf (100 nM), this ET-1-induced two-phase [Ca2+]i response was completely abolished, whereas Rya (50 microM) only markedly blocked the ET-1-induced large global Ca2+ increase. Functional studies showed that 100 nM Baf significantly attenuated ET-1-induced maximal constriction from 82.26 +/- 4.42% to 51.80 +/- 4.36%. Our results suggest that a lysosome-mediated Ca2+ regulatory mechanism via NAADP contributes to ET-1-induced Ca2+ mobilization in CASMCs and consequent vasoconstriction of coronary arteries.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium Signaling / physiology*
  • Cattle
  • Cells, Cultured
  • Coronary Vessels / cytology
  • Coronary Vessels / drug effects
  • Coronary Vessels / metabolism*
  • Dose-Response Relationship, Drug
  • Endothelin-1 / administration & dosage*
  • Lysosomes / drug effects
  • Lysosomes / metabolism*
  • Myocytes, Cardiac / drug effects
  • Myocytes, Cardiac / physiology*
  • NADP / analogs & derivatives*
  • NADP / biosynthesis


  • Endothelin-1
  • NADP
  • Calcium