Conducted signals within arteriolar networks initiated by bioactive amino acids
Frame, M.D.
American Journal of Physiology 276(3): H1012-H1021
1999
ISSN/ISBN: 0002-9513 PMID: 10070086 Document Number: 501692
Our purpose was to determine the specificity of L-arginine ( L-Arg)-induced conducted signals for intra- vs. extracellular actions of L-Arg. Diameter and red blood cell velocities were measured for arterioles 1,000 mm upstream from the local (micropipette) application. Six amino acids were tested: L-arginine, L-cystine, L-leucine, L-lysine, L-histidine, and L-aspartate (100 mM each). Only L-Arg induced a remote dilation; L-lysine and L-aspartate had no effect, and the others each induced a significant remote constriction. There is a second conducted signal initiated by L-arginine that preconditions the arteriolar network and upregulates a direct response of L-arginine to dilate the remote site. This was blocked by inhibition of L-arginine uptake at the local (preconditioning) site (100 mM L-histidine or 1 mM phenformin). Arginine-glycine-aspartate (100 mM)-induced remote dilations (+3.2 ± 0.3 mm) were not mimicked by a peptide control and were prevented by anti-integrin av monoclonal antibody. Remote dilations were greater in animals with a higher wall shear stress for arginine-glycine-aspartate (r2 = 0.92) but not for L-arginine (r2 = 0.12). Thus L-arginine initiates separate conducted signals related to system y+ transport, integrins, and baseline flow. Reprinted by permission of the publisher.