Atrial natriuretic peptides and urodilatin modulate proximal tubule Na+-ATPase activity through activation of the NPR-A/cGMP/PKG pathway

Abstract

The signaling pathway mediating modulation of Na(+)-ATPase of proximal tubule cells by atrial natriuretic peptides (ANP) and urodilatin through receptors located in luminal and basolateral membranes (BLM) is investigated. In isolated BLM, 10(-11)M ANP or 10(-11)M urodilatin inhibited the enzyme activity (50%). Immunodetection revealed the presence of NPR-A in BLM and LLC-PK1 cells. Both compounds increased protein kinase G (PKG) activity (80%) and this effect did not occur with 10(-6)M LY83583, a specific inhibitor of guanylyl cyclase. The inhibitory effect of these peptides on Na(+)-ATPase activity did not occur after addition of 10(-6)M KT5823, a specific inhibitor of PKG. LLC-PK1 cells were used to investigate if ANP and urodilatin change the activity of sodium pumps by luminal receptor interaction. ANP and urodilatin inhibited Na(+)-ATPase activity (50%), with maximal effect at 10(-10)M, similar to 10(-7)M db-cGMP, and did not occur with 10(-7)M LY83583, a guanylyl cyclase inhibitor. ANP and urodilatin specifically inhibit Na(+)-ATPase activity by activation of the cGMP/PKG pathway through NPR-A located in luminal membrane and BLM, increasing understanding of the mechanism of natriuretic peptides on renal sodium excretion, with proximal tubule Na(+)-ATPase one possible target.

An Unsuspected Property of Natriuretic Peptides

“…39 As a positive control, 8-bromo-cGMP (1 μM) increased PKG activity by ~50% (Figure 5B). Furthermore, BNP (100 nM) caused a ~2.5-fold increase in cAMP level in PC12 cells, which was mimicked by both 8-bromo-cGMP (1 μM) and 8-pCPT-cGMP (3 μM), but prevented by the PKG inhibitor (0.5 μM).…”

Proximal Nephron

“…Through the 1980s and the early 1990s, we reasoned that humoral mediators which have direct actions on GFR and sodium and fluid reabsorption in proximal tubules may play additional and important roles in the regulation of GTB. Among these humoral factors or mediators, ANG II (202; 527; 582; 587), atrial natriuretic peptide (105; 107; 196; 197; 332; 376; 398; 519; 589), endothelin 1 (201; 292; 293; 314; 560), and dopamine (11; 104) appear to directly or indirectly affect GFR and absolute proximal reabsorption and therefore GTB. This section of review focuses primarily on the roles of these systemic and intrarenal humoral factors or mediators in the regulation of absolute proximal reabsorption and GTB.…”

Angiotensin II-mediated biphasic regulation of proximal tubular Na+/H+ exchanger 3 is impaired during oxidative stress

“…These data show that at high concentration ANG II inhibits NHE3 via PKG activation. It has been shown that natriuretic peptides inhibit renal Na ϩ -K ϩ -ATPase activity via natriuretic peptide receptor-cGMP-PKG pathways (29). Since oxidative stress can reduce the cGMP-induced PKG stimulation (26), the failure of ANG II to activate PKG could explain the loss of biphasic response in BSO-treated rats.…”

“…Also, the role of nitric oxide (NO) as a natriuretic factor is still not clear because millimolar concentrations of NO donors are required to raise cGMP levels and inhibit sodium transporters (6). However, natriuretic factors can increase proximal tubular cGMP levels via activation of particulate guanylyl cyclase and regulate sodium transporters (29). Therefore, this study is also aimed to identify the signaling molecules involved in ANG II-mediated NHE3 inhibition.…”