Uridine adenosine tetraphosphate induces contraction and relaxation in rat aorta

• Published in: Vascular pharmacology Vol. 48; no. 4; pp. 202 - 207
• Main Authors: Linder, A. Elizabeth, Tumbri, Michelle, Linder, Felipe F.P., Webb, R. Clinton, Leite, Romulo
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.04.2008
• Subjects: Animals; Aorta, Thoracic - drug effects; Calcium Channel Blockers - pharmacology; Calcium Channels, L-Type - drug effects; Cardiovascular; Contraction; Dinucleoside Phosphates - pharmacology; Endothelium, Vascular - drug effects; Endothelium, Vascular - physiology; In Vitro Techniques; Male; Muscle Contraction - drug effects; Muscle Relaxation - drug effects; Muscle, Smooth, Vascular - drug effects; Nitric Oxide - metabolism; Purinergic receptors; Rat aorta; Rats; Rats, Sprague-Dawley; Receptors, Purinergic P1 - drug effects; Receptors, Purinergic P2 - drug effects; Relaxation; rho-Associated Kinases - antagonists & inhibitors; Superoxides - metabolism; Tachyphylaxis - physiology; Uridine adenosine tetraphosphate; Rat aorta; Relaxation; Uridine adenosine tetraphosphate; Purinergic receptors; Contraction
• ISSN: 1537-1891; 1879-3649
• DOI: 10.1016/j.vph.2008.03.003

Uridine adenosine tetraphosphate (Up 4A) has been recently reported as an endothelium-derived vasoconstrictor and plasma levels of this dinucleotide are increased in juvenile hypertensive subjects. This study aimed to evaluate the vascular actions of Up 4A, typify the putative purinergic receptors that might mediate these effects and characterize the intracellular signaling pathways that may govern Up 4A responses. Up 4A induced a modest endothelium-dependent relaxation of rat aortic rings contracted with phenylephrine. From baseline, Up 4A induced concentration-dependent contractions that were significantly potentiated by endothelium removal or nitric oxide synthase inhibition. The contractile response induced by Up 4A was not tachyphylactic and was significantly reduced in the presence of P1 or P2X receptor antagonists, L-type Ca 2+ channel blocker and Rho-kinase inhibitor. Up 4A-induced contraction apparently involves superoxide anion formation since it was significantly reduced by treatment with apocynin or tempol. This study presents the unique findings that the endogenous compound Up 4A is able to induce relaxation in addition to contraction of rat aorta. Up 4A-induced contraction is modulated by nitric oxide production, mediated by P1 and P2X receptor activation, and involves L-type Ca 2+ channels, Rho-kinase pathway and superoxide formation.