Characterisation of P2X receptors expressed in rat pulmonary arteries.
Previous studies indicated that a P2X receptor other than the P2X1 subtype might be present in rat large, but not small pulmonary arteries. The aim here was to characterise further these P2X receptors. Isometric tension was recorded from rat isolated small (i.d. 250-500 μm) and large pulmonary artery (i.d. 1-1.5 mm) rings mounted on a wire myograph. In both tissues the P2X receptor agonist α,β-meATP evoked rapidly-developing contractions that were inhibited by the P2X antagonists NF449, PPADS and suramin in a concentration-dependent manner and eventually abolished by each. The rank order of the potency in both tissues was NF449>PPADS=suramin. For each antagonist there was no significant difference between its potency in the small and large pulmonary arteries. Prolonged administration of a high concentration of α,β-meATP induced complete desensitisation in both tissues. RT-PCR followed by PCR with specific oligonucleotide primers, identified mRNA for all seven P2X subunits. Subtype-specific antibodies showed strong, punctate P2X1 receptor-like immunoreactivity in the majority of cells and faint, punctate staining with the anti-P2X2 and anti-P2X4 antibodies, whilst P2X5-like immunoreactivity was barely detectable and no P2X3, P2X6, and P2X7 receptor-like immunoreactivity was seen. No differences in P2X mRNA and protein expression were seen between small and large pulmonary arteries. In conclusion, the pharmacological properties and mRNA and protein expression profiles of P2X receptors in rat small and large pulmonary arteries are very similar. Thus P2X1 appears to be the predominant P2X subunit functionally expressed in smooth muscle cells of rat small and large pulmonary arteries.
Syed
Nawazish-i-Husain
NI
Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, John Arbuthnott Building, 27 Taylor Street, Glasgow G4 ONR, United Kingdom. snihusain@yahoo.com
Tengah
Asrin
A
Paul
Andrew
A
Kennedy
Charles
C
D000818:Animals; D015536:Down-Regulation / Q000187:drug effects; D015870:Gene Expression; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D008168:Lung / Q000098:blood supply*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D009994:Osmolar Concentration; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011651:Pulmonary Artery / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D058911:Purinergic P2X Receptor Agonists / Q000494:pharmacology; D058920:Purinergic P2X Receptor Antagonists / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D058469:Receptors, Purinergic P2X / Q000235:genetics / Q000378:metabolism*; D058474:Receptors, Purinergic P2X1 / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014662:Vasoconstrictor Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology
D021122:Protein Subunits; D058911:Purinergic P2X Receptor Agonists; D058920:Purinergic P2X Receptor Antagonists; D012333:RNA, Messenger; D058469:Receptors, Purinergic P2X; D058474:Receptors, Purinergic P2X1; D014662:Vasoconstrictor Agents