DYE TRACERS DEFINE DIFFERENTIAL ENDOTHELIAL AND SMOOTH-MUSCLE COUPLING PATTERNS WITHIN THE ARTERIOLAR WALL

Dye tracers were chosen, based on net charge, chemical structure, and reactive groups, to test for the existence of and to provide novel ins ight into channel selectivities of junctional pathways connecting smoo th muscle and endothelial cells of the arteriolar wall. Dyes were inje cted into individual smooth muscle or endothelial cells of hamster che ek pouch arterioles using microiontophoresis. Coupling, independent of tracer net charge, was seen both within and between cell layers. Endo thelial cells were well coupled by all of the tested dyes. Smooth musc le junctions appeared less effective in dye transfer than endothelial junctions. Lucifer yellow was confirmed to be a poor tracer of smooth muscle gap junctions, and remarkably this dye and other related sulfat e-containing molecules interfered with dye movement through smooth mus cle but not endothelial junctions. Myoendothelial junctions showed a s triking polarity of dye movement, with dye transfer from endothelial t o smooth muscle cells but little or no transfer in the reverse directi on. Because the dyes have size and charge characteristics similar to t hose of known cellular second messengers, these findings have importan t implications for cell-cell signaling in the vessel wall.