title: Evidence for a calcium-sensing receptor in the vascular smooth muscle cells of the spiral modiolar artery.
abstract: The vascular diameter of the gerbilline spiral modiolar artery has been shown to depend on the presence of extracellular Ca(2+) but it remained unknown whether the smooth muscle cells of this arteriole contain a Ca(2+) sensing receptor (CaSR). The cytosolic Ca(2+) concentration ([Ca(2+)](i)) was monitored as fluo 3 fluorescence and the vascular diameter was measured by video-microscopy in isolated in vitro superfused spiral modiolar arteries. RT-PCR was used to probe for the presence of CaSR transcripts. Increasing the extracellular Ca(2+) concentration ([Ca(2+)](o)) from 1 to 10 mm caused a biphasic increase in [Ca(2+)](i) that was paralleled by a vasoconstriction. The initial rate of this vasoconstriction, 2.01 +/- 0.07 microm/sec (n = 131), was inhibited when cytosolic Ca(2+) stores were presumably depleted with thapsigargin (IC(50) = 3 x 10(-9) m, n = 26) or ryanodine (IC(50) = 4 x 10(-8) m, n = 25) or when PLC was inhibited by 10(-6) m U73122 (n = 8). The initial rate of this constriction was not affected by the L-type Ca(2+) channel blocker 10(-6) m nifedipine (n = 5), by 10(-6) m U73343 (n = 6), which is the inactive analogue of U73122, by the T-type Ca(2+) channel blocker 10(-6) Gd(3+) (n = 6) or the Na(+)/Ca(2+) exchanger blocker 10(-4) m Ni(2+) (n = 5). The agonist rank potency order was Gd(3+) > Ni(2+) > Ca(2+) >> neomycin = Mg(2+). Analysis of RNA isolated from the SMA revealed a RT-PCR product of the appropriate size for the CaSR (448 bp). Sequence analysis of the amplified cDNA fragment revealed a 94-96% amino acid identity compared to other CaSRs. These results demonstrate that the spiral modiolar artery contains a CaSR, which is most likely located in the vascular smooth muscle cells.
authors.affiliation: Cell Physiology Laboratory, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: K
authors.initials: K
authors.lastname: Wonneberger
authors.forename: M A
authors.initials: MA
authors.lastname: Scofield
authors.forename: P
authors.initials: P
authors.lastname: Wangemann
mesh_terms: D001158:Arteries / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002413:Cations, Divalent; D003051:Cochlea / Q000098:blood supply; D018076:DNA, Complementary; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D009532:Nickel / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D044169:Receptors, Calcium-Sensing; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D002413:Cations, Divalent; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D004963:Estrenes; D011760:Pyrrolidinones; D044169:Receptors, Calcium-Sensing; D011956:Receptors, Cell Surface; D014665:Vasodilator Agents; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C074854:U 73343; D012433:Ryanodine; D019284:Thapsigargin; D009532:Nickel; D010738:Type C Phospholipases; D009543:Nifedipine; D002118:Calcium