title: Propagated endothelial Ca2+ waves and arteriolar dilation in vivo: measurements in Cx40BAC GCaMP2 transgenic mice.
abstract: To study endothelial cell (EC)- specific Ca(2+) signaling in vivo we engineered transgenic mice in which the Ca(2+) sensor GCaMP2 is placed under control of endogenous connexin40 (Cx40) transcription regulatory elements within a bacterial artificial chromosome (BAC), resulting in high sensor expression in arterial ECs, atrial myocytes, and cardiac Purkinje fibers. High signal/noise Ca(2+) signals were obtained in Cx40(BAC)-GCaMP2 mice within the ventricular Purkinje cell network in vitro and in ECs of cremaster muscle arterioles in vivo. Microiontophoresis of acetylcholine (ACh) onto arterioles triggered a transient increase in EC Ca(2+) fluorescence that propagated along the arteriole with an initial velocity of approximately 116 microm/s (n=28) and decayed over distances up to 974 microm. The local rise in EC Ca(2+) was followed (delay, 830+/-60 ms; n=8) by vasodilation that conducted rapidly (mm/s), bidirectionally, and into branches for distances exceeding 1 mm. At intermediate distances (300 to 600 microm), rapidly-conducted vasodilation occurred without changing EC Ca(2+), and additional dilation occurred after arrival of a Ca(2+) wave. In contrast, focal delivery of sodium nitroprusside evoked similar local dilations without Ca(2+) signaling or conduction. We conclude that in vivo responses to ACh in arterioles consists of 2 phases: (1) a rapidly-conducted vasodilation initiated by a local rise in EC Ca(2+) but independent of EC Ca(2+) signaling at remote sites; and (2) a slower complementary dilation associated with a Ca(2+) wave that propagates along the endothelium.
authors.affiliation: Biomedical Sciences Department, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Yvonne N
authors.initials: YN
authors.lastname: Tallini
authors.forename: Johan Fredrik
authors.initials: JF
authors.lastname: Brekke
authors.forename: Bo
authors.initials: B
authors.lastname: Shui
authors.forename: Robert
authors.initials: R
authors.lastname: Doran
authors.forename: Seong-min
authors.initials: SM
authors.lastname: Hwang
authors.forename: Junichi
authors.initials: J
authors.lastname: Nakai
authors.forename: Guy
authors.initials: G
authors.lastname: Salama
authors.forename: Steven S
authors.initials: SS
authors.lastname: Segal
authors.forename: Michael I
authors.initials: MI
authors.lastname: Kotlikoff
mesh_terms: D000818:Animals; D001160:Arterioles / Q000502:physiology*; D020013:Calcium Signaling / Q000235:genetics* / Q000502:physiology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000235:genetics* / Q000502:physiology; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics / Q000502:physiology; D017630:Connexins / Q000235:genetics* / Q000502:physiology; D004730:Endothelium, Vascular / Q000502:physiology*; D052139:Intracellular Calcium-Sensing Proteins / Q000235:genetics* / Q000502:physiology; D051379:Mice; D008822:Mice, Transgenic; D014664:Vasodilation / Q000235:genetics*; D000097003:Gap Junction alpha-5 Protein
chemical_list: D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017630:Connexins; D052139:Intracellular Calcium-Sensing Proteins; D000097003:Gap Junction alpha-5 Protein