P2X Receptor Immunoreactivity in Different Arteries from the Femoral, Pulmonary, Cerebral, Coronary and Renal Circulations

The expression of the seven P2X receptor subunits (P2X₁–₇) in the rat vascular system was determined using subtype-selective antibodies. Arteries of different sizes (from arterioles to conduit vessels) from a range of vascular beds were used to give an overview of receptor expression. P2X₁ receptor immunoreactivity was detected in the smooth muscle layer of arteries. The relative level of P2X₁ receptor immunoreactivity was dependent on the size of the artery and the vascular bed; expression was highest in small and medium arteries. P2X₄ receptors were detected in all arteries; once again, the relative level of expression was dependent on the size of the artery and the vascular bed. P2X₅ receptor immunoreactivity was barely detectable in most arteries studied. P2X₇ receptor immunoreactivity was generally punctate and associated with the outer adventitial layer. Immunoreactivity for P2X₂, P2X₃ and P2X₆ receptors was not detected in arteries. These results demonstrate that arteries express multiple P2X receptor subunits and that there is a heterogeneity in the level of expression. The properties of artery P2X receptors correspond to homomeric P2X₁ receptors, and the function of P2X₄ and P2X₅ receptor subunits in arteries is unclear.