Identification and function of adenosine A_3 receptor in afferent arterioles

摘要

Adenosine plays an important role in regulation of renal microcirculation. All receptors of adenosine, A_1, A_(2A), A_(2B), and A3, have been found in the kidney. However, little is known about the location and function of the A_3 receptor in the kidney. The present study determined the expression and role of A3 receptors in mediating the afferent arteriole (Af-Art) response and studied the interaction of A3 receptors with angiotensin II (ANG II), A_1 and A_2 receptors on the Af-Art. We found that the A3 receptor expressed in microdissected isolated Af-Art and the mRNA levels of A_3 receptor were 59% of A_1. In the isolated microperfused Af-Art, A_3 receptor agonist IB-MECA did not have a constrictive effect. Activation of A_3 receptor dilated the precon-stricted Af-Art by norepinephrine and blunted the vasoconstrictive effect of both adenosine A_1 receptor activation and ANG II on the Af-Art, respectively. Selective A2 receptor antagonist (both A_(2A) and A_(2B)) had no effect on A_3 receptor agonist-induced vasodilation, indicating that the dilatory effect of A_3 receptor activation is not mediated by activation of A_2 receptor. We conclude that the A_3 receptor is expressed in the Af-Art, and activation of the A_3 receptor dilates the Af-Art.