Journal
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
Volume 280, Issue 2, Pages H767-H776Publisher
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpheart.2001.280.2.H767
Keywords
ATP; cerebral circulation; UTP; purine receptors; pyrimidine receptors
Funding
- NHLBI NIH HHS [HL-57540] Funding Source: Medline
- NINDS NIH HHS [NS-30555] Funding Source: Medline
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Effects of extraluminal UTP were studied and compared with vascular responses to ATP and its analogs in rat cerebral-penetrating arterioles. UTP, UDP, 2-methylthio-ATP, and alpha,beta -methylene-ATP dilated arterioles at the lowest concentration and constricted them at high concentrations. Low concentrations of ATP dilated the vessels; high concentrations caused a biphasic response, with transient constriction followed by dilation. Endothelial impairment inhibited ATP- and UTP-mediated dilation and potentiated constriction to UTP but not to ATP. ATP- and 2-methylthio-ATP- but not UTP-mediated constrictions were inhibited by desensitization with 10(-6) M alpha,beta -methylene-ATP or 3 x 10(-6) M pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS). PPADS at 10(-4) M abolished the UTP-mediated constriction and induced vasodilation in a dose-dependent manner but did not affect the dilation to ATP. These results suggest that in rat cerebral microvessels 1) ATP and 2-methylthio-ATP induce transient constriction via smooth muscle P-2X1 receptors in the cerebral arteriole, 2) UTP stimulates two different classes of P-2Y receptors, resulting in constriction (smooth muscle P-2Y4) and dilation (possibly endothelial P-2Y2), and 3) ATP and UTP produce dilation by stimulation of a single receptor (P-2Y2).
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