Purine- and pyrimidine-induced responses and P2Y receptor characterization in the hamster proximal urethra.
1. Purine and pyrimidine compounds were investigated on hamster proximal urethral circular smooth muscle preparations. In situ hybridization studies were carried out to localize P2Y(1), P2Y(2), P2Y(4) and P2Y(6) mRNA. Protein expression was studied using Western blotting analysis with antibodies against P2Y(1) and P2Y(2) receptors. 2. The hamster urethra relaxed with an agonist potency order of: 2-MeSADP>beta,gamma-meATP=ATP=adenosine=ADP>2-MeSATP>alpha,beta-meATP>TTP>CTP=UTP>GTP=UDP. The high potency of 2-MeSADP is suggestive of an action via P2Y(1) receptors. Although the order is not characteristic for any known single P2Y receptor subtype, it may represent a combination of P2Y receptor subtypes. 4. The selective P2Y(1) receptor antagonist MRS2179 inhibited ATP-, 2-MeSADP-, 2-MeSATP-, beta,gamma-meATP-, and to a lesser degree alpha,beta-meATP-induced responses. 3. Adenosine, but not ATP, was inhibited by the adenosine receptor antagonist 8-phenyltheophylline, indicating that ATP was not acting via adenosine following enzymatic breakdown. 5. Western blotting analysis showed the expression of both P2Y(1) and P2Y(2) receptors, confirming the results obtained with in situ hybridization that showed the expression of both P2Y(1) and P2Y(2), but not P2Y(4) or P2Y(6) mRNA, in smooth muscle layers of the hamster proximal urethra. 6. It is proposed that the relaxant response of the urethra to ATP may be evoked through the activation of the combination of receptors for P2Y(1) and to a lesser extent P2Y(2) receptors, which may mediate a trophic effect in addition. A P2Y subtype responsive to alpha,beta-meATP and P1 receptors may contribute to urethral smooth muscle relaxation.
Pinna
Christian
C
Department of Pharmacological Sciences, University of Milan, via Balzaretti 9, 20133 Milan, Italy.
Glass
Rainer
R
Knight
Gillian E
GE
Bolego
Chiara
C
Puglisi
Lina
L
Burnstock
Geoffrey
G
D000818:Animals; D015153:Blotting, Western; D006224:Cricetinae; D017403:In Situ Hybridization; D066298:In Vitro Techniques; D008297:Male; D008647:Mesocricetus; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D058915:Purinergic P1 Receptor Antagonists; D058919:Purinergic P2 Receptor Antagonists; D011687:Purines / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D018048:Receptors, Purinergic P2 / Q000096:biosynthesis*; D014521:Urethra / Q000187:drug effects* / Q000378:metabolism
D058915:Purinergic P1 Receptor Antagonists; D058919:Purinergic P2 Receptor Antagonists; D011687:Purines; D011743:Pyrimidines; D018048:Receptors, Purinergic P2