Purinergic receptors in the splanchnic circulation

Abstract

There is considerable evidence that purines are vasoactive molecules involved in the regulation of blood flow. Adenosine is a well known vasodilator that also acts as a modulator of the response to other vasoactive substances. Adenosine exerts its effects by interacting with adenosine receptors. These are metabotropic G-protein coupled receptors and include four subtypes, A 1 , A 2A , A 2B and A 3 . Adenosine triphosphate (ATP) is a co-transmitter in vascular neuroeffector junctions and is known to activate two distinct types of P2 receptors, P2X (ionotropic) and P2Y (metabotropic). ATP can exert either vasoconstrictive or vasorelaxant effects, depending on the P2 receptor subtype involved. Splanchnic vascular beds are of particular interest, as they receive a large fraction of the cardiac output. This review focus on purinergic receptors role in the splanchnic vasomotor control. Here, we give an overview on the distribution and diversity of effects of purinergic receptors in splanchnic vessels. Pre-and post-junctional receptormediated responses are summarized. Attention is also given to the interactions between purinergic receptors and other receptors in the splanchnic circulation.

Decreases in splanchnic vascular resistance contribute to hypotensive effects ofl-serine in hypertensive rats

“…Blood flow to this region accounts for 25% of the overall CO, and it is enhanced in the postprandial state (11,28). The intrinsic mechanisms and the metabolic factors that govern intestinal vasodilatation under such conditions are not fully understood, but adenosine is recognized as a potent vasodilator of the splanchnic vascular bed (27). It is not known whether L-serine-induced vasodilatation is linked in some ways to vascular adenosine receptor activation/purinergic transmission (27).…”

“…The intrinsic mechanisms and the metabolic factors that govern intestinal vasodilatation under such conditions are not fully understood, but adenosine is recognized as a potent vasodilator of the splanchnic vascular bed (27). It is not known whether L-serine-induced vasodilatation is linked in some ways to vascular adenosine receptor activation/purinergic transmission (27). Alternatively, it is also possible that L-serine is transported through the neutral amino acid transporter, LAT-1, into endothelial cells, and the movement of L-serine through this transporter may be linked to activation of endothelial K Ca channels to promote vasodilatation (20).…”

Purinergic Signaling and Blood Vessels in Health and Disease

“…There is a more recent review of purinergic receptors in the splanchnic microcirculation (Morato et al, 2008). …”

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“…This was first noted on MR perfusion imaging in terms of a visual attenuation of splenic perfusion during adenosine application. 14 Initial studies suggest that the splenic switch-off sign is a more reliable marker of hemodynamic response to adenosine application than changes in heart rate, blood pressure or the occurrence of physical symptoms. 15 The problem that the switch-off sign can only be seen following contrast media application has been overcome by using a native T1-mapping technique for the quantification of tissue blood volumes without contrast application.…”