Abstract Body (Do not enter title and authors here): Background: Coronary autoregulation is the ability of a normal heart to maintain constant coronary blood flow (CBF) over a wide range of coronary driving pressures (CDPs) provided cardiac work remains constant. It is based on the myogenic response, the molecular mechanism of which is unknown. We recently described the presence of a G-protein coupled receptor (GPR39) in the vascular smooth muscle cells (VSMCs) of coronary arterioles in the mouse heart. We showed that endogenous eicosanoids, the vasoconstrictor 15-hydroxyeicosatetraenoic acid (15-HETE) and the vasodilator 14,15-epoxyeicosatrienoic acid (14,15 EET). act through this receptor to maintain coronary vascular tone.
Hypothesis: We, therefore, hypothesized that GPR39 is the molecular switch responsible for the coronary myogenic response and autoregulation.
Methods: We studied 6 anesthetized dogs at baseline and after administration of VC-108, a specific, potent GPR39 antagonist. Both during baseline and drug administration multiple coronary stenoses were created on the left anterior descending coronary artery (LAD). At each stage, heart rate, mean aortic pressure, distal LAD pressure, and right atrial pressure (RAP) were measured, as was CBF. Stenosis severity was defined by the CDP (LAD pressure minus RAP).
Results: Mean basal coronary hyperemic response was 3.0 in all anesthetized animals indicating normal vasomotor function. Systemic hemodynamics did not differ between baseline and drug stages. Figure 1 is an example from a single dog where, at baseline, CBF remained constant over a CDP of 40-90 mm Hg indicating intact autoregulation. As expected, CBF declined when CDP fell below the autoregulatory range. After VC-108 administration CBF correlated linearly with CDP, indicating abolishment of the myogenic response. Baseline CDP vs. CBF data from all 6 animals within the autoregulatory range is depicted in Figure 2. No relation is noted between the two indicating intact autoregulation. In contrast, CDP vs. CBF relation is linear in all animals after VC108 is administered over the entire range of CDP’s measured, indicating abolishment of autoregulation (Figure 3).
Conclusions: Our results indicate that GPR39 is a potential molecular switch for the regulation of the myogenic response underlying coronary autoregulation. Pharmacological blockage of GPR39 abolishes the myogenic tone. These novel findings set the stage for development of novel pharmacological agents for treatment of coronary artery disease.