title: Intercellular calcium signaling and nitric oxide feedback during constriction of rabbit renal afferent arterioles.
abstract: Vasoconstriction and increase in the intracellular calcium concentration ([Ca(2+)](i)) of vascular smooth muscle cells may cause an increase of endothelial cell [Ca(2+)](i), which, in turn, augments nitric oxide (NO) production and inhibits smooth muscle cell contraction. This hypothesis was tested in microperfused rabbit renal afferent arterioles, using fluorescence imaging microscopy with the calcium-sensitive dye fura-2 and the NO-sensitive dye 4-amino-5-methylamino-2',7'-difluorescein. Both dyes were loaded into smooth muscle and endothelium. Depolarization with 100 mmol/l KCl led to a transient vasoconstriction which was converted into a sustained response by N-nitro-l-arginine methyl ester (l-NAME). Depolarization increased smooth muscle cell [Ca(2+)](i) from 162 +/- 15 nmol/l to a peak of 555 +/- 70 nmol/l (n = 7), and this response was inhibited by 80% by the l-type calcium channel blocker calciseptine. After a delay of 10 s, [Ca(2+)](i) increased in endothelial cells immediately adjacent to reactive smooth muscle cells, and this calcium wave spread in a nonregenerative fashion laterally into the endothelial cell layer with a velocity of 1.2 microm/s. Depolarization with 100 mmol/l KCl led to a significant increase in NO production ([NO](i)) which was inhibited by l-NAME (n = 5). Acetylcholine caused a rapid increase in endothelial [Ca(2+)](i), which did not transfer to the smooth muscle cells. l-NAME treatment did not affect changes in smooth muscle [Ca(2+)](i) after depolarization, but it did increase the calcium sensitivity of the contractile apparatus. We conclude that depolarization increases smooth muscle [Ca(2+)](i) which is transferred to the endothelial cells and stimulates NO production which curtails vasoconstriction by reducing the calcium sensitivity of the contractile apparatus.
authors.affiliation: Physiology and Pharmacology, Univ. of Southern Denmark, DK-5000 Odense, Denmark.
authors.forename: T R
authors.initials: TR
authors.lastname: Uhrenholt
authors.forename: J
authors.initials: J
authors.lastname: Schjerning
authors.forename: P M
authors.initials: PM
authors.lastname: Vanhoutte
authors.forename: B L
authors.initials: BL
authors.lastname: Jensen
authors.forename: O
authors.initials: O
authors.lastname: Skøtt
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001160:Arterioles / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D042783:Endothelial Cells / Q000187:drug effects / Q000502:physiology; D005246:Feedback; D008297:Male; D008856:Microscopy, Fluorescence; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000494:pharmacology*; D010477:Perfusion; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*
chemical_list: D009569:Nitric Oxide; D011189:Potassium Chloride; D000109:Acetylcholine; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester