Extracellular nucleotide receptor inhibits AVP-stimulated water permeability in inner medullary collecting duct

Abstract

The P2u class of nucleotide receptors is linked to mobilization of intracellular Ca2+ in many cell types, including the renal collecting duct cells. In the present studies, we examined the effects of nucleotides (ATP, UTP, and ADP; 10 microM each) on the arginine vasopressin (AVP, 0.1 nM)-stimulated osmotic water permeability (Pf) in in vitro perfused terminal inner medullary collecting ducts (IMCD) of rat. ATP or UTP, when added to the bath, decreased the AVP-stimulated Pf by approximately 40%. These effects were reversible upon withdrawal of the nucleotides. However, addition of ADP to the bath or sham exchange of the bath had no significant effect on the Pf. Furthermore, ATP did not have any significant effect on the Pf stimulated either by a membrane-permeant, nonhydrolyzable adenosine 3',5'-cyclic monophosphate (cAMP) analogue [8-(4-chlorophenylthio)-cAMP, 0.1 mM] o by forskolin (1 microM). In line with these findings, ATP decreased the AVP-stimulated cAMP levels in IMCD suspensions to approximately 68%. In addition, ATP did not exert an inhibitory effect on the AVP-stimulated Pf in the presence of calphostin C (150 nM), an inhibitor of protein kinase C. These results lead us to conclude the following: 1) agonist occupancy of the putative nucleotide receptor in the terminal IMCD causes an inhibition of AVP-stimulated Pf; and 2) this effect is due to a decrease in cellular cAMP levels, most likely resulting from activation of the phosphoinositide signaling pathway.

Purinergic signalling in the kidney in health and disease

“…ATP was shown to reversibly inhibit AVPs' actions in isolated perfused rabbit CCD and rat IMCD [187,188,314]. Since UTP and ATP were equipotent, the inhibitory effects were attributed to the activation of P2Y 2 [188].…”

“…PLC activates PKC, which inhibits adenylate cyclase [369]. Indeed the inhibitory effects of P2Y 2 receptors have been shown to be associated with PKC-dependent reductions in cAMP [187]. More recently, COX-1-mediated prostaglandin (PG) E 2 synthesis has also been implicated in ATPs' inhibitory effects.…”

P2Y2 receptors and water transport in the kidney

“…The receptor protein is expressed on both apical and basolateral domains of rat medullary collecting duct [27]. While Kishore and Knepper, as well as others, have demonstrated that the basolateral P2Y 2 receptor is involved in the inhibition of AVP-induced water transport in medullary collecting duct [10,11,14], recent studies have demonstrated a role for the apical P2Y 2 receptor in the inhibition of amiloride-sensitive sodium transport via the epithelial sodium channel (ENaC) in the collecting duct [19,[33][34][35]. P2-receptor-mediated regulation of sodium transport in the collecting duct is dealt with elsewhere in this Special Issue (see articles by Bailey and Shirley [36] and Wildman et al [37]), and so we will not elaborate this aspect here; instead we will focus on regulation of water transport by the P2Y 2 receptor.…”

“…Apart from AVP, a variety of autocrine and paracrine agents, such as prostaglandin E 2 (PGE 2 ), endothelin and extracellular nucleotides (ATP/UTP), can regulate collecting duct water transport [7][8][9][10][11][12][13][14]. Acting through their respective receptors, and the associated phosphoinositide signalling pathway, these agents decrease AVP-stimulated osmotic water permeability in the collecting duct (Fig.…”

“…First, activation of the P2Y 2 receptor per se down regulates AVP-stimulated water transport in a protein kinase C-dependent and inhibitory G protein (Gi)-mediated manner [10,11]. Secondly, activation of the P2Y 2 receptor causes the production and release of PGE 2 by the medullary collecting duct [30].…”