Conducted signals within arteriolar networks initiated by bioactive amino acids.

Our purpose was to determine the specificity of l-arginine (l-Arg)-induced conducted signals for intra- vs. extracellular actions ofl-Arg. Diameter and red blood cell velocities were measured for arterioles [18 ± 1.6 (SE) μm] in the cremaster muscle of pentobarbital sodium-anesthetized (Nembutal, 70 mg/kg) hamsters ( n = 53). Remote (conducted) responses were viewed ∼1,000 μm upstream from the local (micropipette) application. Six amino acids were tested:l-arginine,l-cystine,l-leucine,l-lysine,l-histidine, andl-aspartate (100 μM each). Only l-Arg induced a remote dilation; l-lysine andl-aspartate had no effect, and the others each induced a significant remote constriction. There is a second conducted signal initiated byl-arginine that preconditions the arteriolar network and upregulates a direct response ofl-arginine to dilate the remote site. This was blocked by inhibition ofl-arginine uptake at the local (preconditioning) site (100 μMl-histidine or 1 mM phenformin). Arginine-glycine-aspartate (100 μM)-induced remote dilations (+3.2 ± 0.3 μm) were not mimicked by a peptide control and were prevented by anti- integrin αv monoclonal antibody. Remote dilations were greater in animals with a higher wall shear stress for arginine-glycine-aspartate ( r 2 = 0.92) but not for l-arginine ( r 2 = 0.12). Thusl-arginine initiates separate conducted signals related to system y+ transport, integrins, and baseline flow.