Connexin 37 and KCa3.1 contribute to P2Y2 receptor initiated endothelial‐derived hyperpolarization (1079.15)

Abstract

Nucleotides such as ATP and UTP are important paracrine regulators of vascular tone. Importantly, we previously demonstrated that in vivo activation of P2Y2 receptors (activated by ATP/UTP) causes an acute NO‐independent decrease in blood pressure (BP), indicating this signaling pathway requires an endothelial‐derived hyperpolarization (EDH) response. To define the mechanisms by which in vivo activation of P2Y2 receptors initiates EDH and vasodilation, we studied connexin 37 and 40 (Cx37, Cx40), both part of the myoendothelial gap junction, as well as big‐conductance (KCa1.1, expressed in smooth muscle cells) and intermediate‐conductance K channels (KCa3.1, expressed in endothelial cells), all hypothesized to be part of the EDH response. We compared the effects of the P2Y2/4 receptor agonist, INS45973, in wild‐type (WT) mice and mice lacking Cx37, Cx40, KCa1.1, or KCa3.1 (n=4‐5/genotype) under anesthesia, while monitoring intra‐arterial BP. Acute application of INS45973 (0.01, 0.03, 0.1, 0.3, 1, or 3 mg/kg bw i.v. in 0.5 µl/g bw over 45 sec) dose‐dependently and rapidly (within 15 sec of starting infusion) decreased BP in WT mice (max response % of baseline: ‐38±1%, EC50: 0.8±0.2 mg/kg) for 2‐3 min. Whereas the responses in Cx40‐/‐ and KCa1.1‐/‐ mice were comparable to WT mice (‐41±2%, 0.3±0.1 mg/kg and ‐44±3%, 0.3±0.1 mg/kg, respectively), responses in Cx37‐/‐ and KCa3.1‐/‐ mice were significantly impaired (‐27±1%, 1.2±0.3 mg/kg and ‐13±5%, 1.6±0.8 mg/kg, respectively). Heart rate was not affected in either genotype. Our data indicate that Cx37 and KCa3.1 are required, at least in part, for the P2Y2 receptor‐initiated EDH response and subsequent vasodilation.Grant Funding Source: 10SDG2610034 and P30DK079337