Stimulation of A_2a adenosine receptor abolishes the inhibitory effect of arachidonic acid on the basolateral 50-pS K channel in the thick ascending limb

Abstract

The basolateral 50-pS K channels are stimulated by a cAMP-dependent pathway and inhibited by cytochrome P-450-omega-hydroxylase-dependent metabolism of arachidonic acid (AA) in the rat thick ascending limb (TAL). We now used the patch-clamp technique to examine whether stimulation of adenosine A(₂a) receptor modulates the inhibitory effect of AA on the basolateral 50-pS K channels in the medullary TAL. Stimulation of adenosine A(₂a) receptor with CGS-21680 or inhibition of phospholipase A₂ (PLA₂) with AACOCF3 increased the 50-pS K channel activity in the TAL. Western blot demonstrated that application of CGS-21680 decreased the phosphorylation of PLA(2) at serine residue 505, an indication of inhibiting PLA₂ activity. In the presence of CGS-21680, inhibition of PLA₂ had no further effect on the basolateral 50-pS K channels. The possibility that CGS-21680-induced stimulation of the basolateral 50-pS K channels was partially achieved by inhibition of PLA₂ in the TAL was also supported by the observation that CGS-21680 had no additional effect in the presence of AACOCF3. Moreover, stimulation of adenosine A(₂a) receptor with CGS-21680 also abolished the inhibitory effect of AA and 20-hydroxyeicosatetraenoic acid (20-HETE) on the 50-pS K channels. The effect of CGS-21680 on AA and 20-HETE-mediated inhibition of the 50-pS K channels was mediated by cAMP because application of membrane-permeable cAMP analog, dibutyryl-cAMP, not only increased the 50-pS K channel activity but also abolished the inhibitory effect of AA and 20-HETE. We conclude that stimulation of adenosine A(₂a) receptor increased the 50-pS K channel activity in the TAL, an effect that is achieved by suppression of PLA₂ activity and 20-HETE-induced inhibition.

Adenosine contribution to normal renal physiology and chronic kidney disease

“…One proposed mechanism of NaCl homeostasis through the adenosine A 2A receptor involves stimulation of K + channels and Clsecretion (Wang et al 2011;Gu et al 2007).…”

Adenosine Effects on Renal Function in the Rat: Role of Sodium Intake and Cytochrome P450

“…In recent studies of isolated kidney preparations, increasing ADO concentration activated the CYP-450 pathway, an effect potentiated by high salt intake [6,12,13]. An interaction of CYP-450-dependent agents with ADO receptors was also demonstrated in isolated tubule segments [14,15]. …”

“…Stimulation of A2R is known to activate the endothelial and possibly also tubular cytochrome P450 (CYP450)-dependent metabolism of arachidonic acid [7,11,12,13,14,15]. Since the major active metabolites of the CYP450 pathway - epoxyeicosatrienoic acids (EETs) and 20-hydroxyeicosatetraenoic acid - are both vasoactive and transport inhibitory, they are likely to mediate the post-ADO changes in excretion.…”

Cytochrome P450 and Lipoxygenase Metabolites on Renal Function

“…Likewise, a deficiency in TALH 20-HETE generation contributes to elevated loop Cl − reabsorption and this 20-HETE administration normalizes Cl − transport in the Dahl salt-sensitive rat (113,136). 20-HETE can also inhibit 50pS K + channels in the TAHL (133). Adenosine A2a receptor activation can abolish the inhibitory effect 20-HETE on the 50pS K + channels (133).…”

“…20-HETE can also inhibit 50pS K + channels in the TAHL (133). Adenosine A2a receptor activation can abolish the inhibitory effect 20-HETE on the 50pS K + channels (133). Angiotensin II and bradykinin inhibitory actions on Na + transport in the TALH are also dependent on 20-HETE (114).…”