COEXPRESSION OF MESSENGER-RNAS FOR P2X(1), P2X(2) AND P2X(4) RECEPTORS IN RAT VASCULAR SMOOTH-MUSCLE - AN IN-SITU HYBRIDIZATION AND RT-PCR STUDY

The expression of mRNAs for three P2X receptor subtypes (PX2(1), P2X(2 ), P2X(4)) in the rat vascular system was studied by in situ hybridiza tion and RT-PCR. In heart sections mRNAs transcripts for all three rec eptors were colocalized in smooth muscle cells of coronary vessels, wh ile no specific positivity was apparent in myocardium. Coexpression of P2X receptor mRNA transcripts were also observed in other peripheral vessels, including aorta, pulmonary artery, internal and external ilia c arteries, renal artery and femoral artery. By contrast, no mRNA tran scripts of the above receptors were found in the superior mesenteric a rtery. RT-PCR performed on microdissected tissues (coronary arteries, aorta and myocardium from various heart areas) confirmed the presence of P2X(1), P2X(2) and P2X(4) receptor mRNAs. Furthermore, in the same tissues two splice variants of the P2X(2) receptor were identified. Th ese results reveal an important molecular heterogeneity of P2X recepto rs, thus substantiating the possibility of a heteropolymeric assembly of ATP-gated ion channels in the cardiovascular system.