APPS November 2002 Meeting Abstract 2437

Lele Jiang^1,2, Michelle Bardini², Cristobal G. dos Remedios¹, Geoffrey Burnstock², 1Institute for Biomedical Research, Department of Anatomy and Histology, the University of Sydney, NSW, 2 Autonomic Neuroscience Institute, Royal Free Hospital School of Medicine, Rowland Hill Street, London NW3 2PF, UK.

The heart has long been known to respond to purinergic agents¹. In this study we examined the expression and localization of P2X₁ receptors in human left ventricles (LV) in non-diseased control and failing hearts with dilated cardiomyopathy (DCM). Using immunohistochemistry, we detected P2X₁ expression predominantly in the intercalated discs. Further study showed the distribution of P2X₁ is close to that of the gap junction protein connexin43; however the fluorescence staining patterns of the two proteins do not overlay each other indicating they are spatially discrete. Western blotting using polyclonal antibody against P2X₁ detected four major bands at 45, 60, 95 and 120 kDa in the protein extracts from human LV. They correspond to equivalent protein bands from rat vas deferens known to express P2X₁². The most prominent band in human LV was a 95 kDa protein, possibly a dimer of the native P2X₁ receptor, whereas in vas deferens it was the 60 kDa band. After preincubation of the antibody with its epitope peptide, the 45 and 60 kDa bands almost disappeared and the 95 and 120 kDa bands were significantly attenuated. These data suggest that P2X₁ receptors are expressed in human heart muscles. Localization of P2X₁ receptors is close to but does not overlay connxin43 expression in the intercalated discs. No obvious difference in the distribution of P2X₁ receptors was found in failing LV with DCM.