Rat Strain Effects of AT ₁ Receptor Activation on D ₁ Dopamine Receptors in Immortalized Renal Proximal Tubule Cells

Abstract

Abstract-The dopaminergic and renin-angiotensin systems regulate blood pressure, in part, by affecting sodium transport in renal proximal tubules (RPTs). We have reported that activation of a D 1 -like receptor decreases AT 1 receptor expression in the mouse kidney and in immortalized RPT cells from Wistar-Kyoto (WKY) rats. The current studies were designed to test the hypothesis that activation of the AT 1 receptor can also regulate the D 1 receptor in RPT cells, and this regulation is aberrant in spontaneously hypertensive rats (SHRs Key Words: dopamine Ⅲ kidney Ⅲ receptors, angiotensin II Ⅲ rats, spontaneously hypertensive A ngiotensin II and dopamine are important regulators of sodium and water transport across the renal proximal tubule (RPT). [1][2][3][4][5][6][7][8] Angiotensin II receptor subtypes (AT 1 , AT 2 , and AT 4 ) are expressed in brush border and basolateral membranes of RPTs. [1][2][3][4][5] The activation of AT 1 receptors by low concentrations of angiotensin II (picomolar) causes an increase in sodium reabsorption in RPTs. 1,3,6 All the dopamine receptor subtypes, D 1 -like (D 1 and D 5 ) and D 2 -like (D 2 , D 3 , and D 4 ) are also expressed in brush border and basolateral membranes of RPTs. [7][8][9][10] In contrast to the stimulatory effect of AT 1 receptors on renal sodium transport, activation of D 1 and D 3 receptors decreases renal sodium reabsorption. 7,8,[11][12][13] Several reports have shown an interaction between the dopamine and renin-angiotensin system. Intrarenally produced angiotensin II opposes the natriuretic action of the D1-like dopamine receptor agonist, fenoldopam, in rats. 14 D 2 -like receptor agonists also antagonize the stimulatory effect of angiotensin II, acting via AT 1 receptors, on renal proximal tubular luminal sodium transport. 15,16 When angiotensin II generation is inhibited or AT 1 receptors are blocked, the natriuretic effect of dopaminergic drugs is enhanced. 17 The AT 1 receptor mediates the anti-natriuretic effect of angiotensin II, whereas the D 1 dopamine receptor is responsible for Ϸ80% of D 1 -like receptor activity in RPTs. 18 We have reported that in RPT cells of Wistar-Kyoto (WKY) Methods Cell CultureImmortalized RPT cells from 4-to 8-week-old WKY and SHRs were cultured at 37°C in 95% air/5% CO 2 atmosphere in DMEM/F-12 culture media, as previously described. [21][22][23][24][25][26] The cells (80% confluence) were extracted in ice-cold lysis buffer (phosphate-buffered saline with 1% NP40, 0.5% sodium deoxycholate, 0.1% SDS, 1 mmol/L EDTA, 1 mmol/L EGTA, 1 mmol/L PMSF, 10 g/mL aprotinin, and 10 g/mL leupeptin), sonicated, kept on ice for 1 hour, and centrifuged at 16 000g for 30 minutes. The supernatants were stored at Ϫ70°C until use for immunoblotting and/or immunoprecipitation. ImmunoblottingThe antibodies are polyclonal purified antipeptides. The amino acid sequence for the immunogenic peptide (rabbit anti-human AT 1 receptor antibody) is QDDCPKAGRHC, amino acids 15 to 24 of the AT 1 receptor. The specificity of this antibody to the AT 1 ...

Negative reciprocity between angiotensin II type 1 and dopamine D1 receptors in rat renal proximal tubule cells

“…The decreased power of interaction between D1R and AT1R following short-term exposure to either receptor agonist cannot therefore be explained by a loss of whole cell receptor protein. Previous studies from the group of Felder and Jose (21) has shown that long-term, generally 24-h, exposure to D1R or AT1R agonists decreases the total abundance of the reciprocal receptor (21).…”

“…Long-term dopamine exposure is known to decrease AT 1 receptors (AT1R) in renal proximal tubular cells (7). Furthermore, studies by Zeng et al (21) have shown that long-term stimulation of AT1R results in an upregulation of D1-like receptors (D1R). This effect was not observed in spontaneously hypertensive rats, indicating that the interaction between AT1R and D1R has an impact on blood pressure regulation.…”

D 3 Dopamine Receptor Directly Interacts With D 1 Dopamine Receptor in Immortalized Renal Proximal Tubule Cells

“…5,6 We hypothesize that D 1 , D 3 , D 4 , and D 5 receptors interact (in RPTs or elsewhere in the nephron) among or between themselves, and/or other GPCRs, such as angiotensin and endothelin receptors, to regulate sodium excretion. 6,7,12,24,32,40,41,55,56 The ultimate effect of dopamine is the sum of the interactions of those dopamine receptor subtypes and other GPCRs that may depend on the state of sodium balance. These interactions are impaired in SHRs.…”

Binding of Losartan to Angiotensin AT1 Receptors Increases Dopamine D1 Receptor Activation

“…[1][2][3] Several lines of evidence suggest that AT1R and D1R form a heteromeric signaling complex. [4][5][6] We recently reported that activation of either AT1R or D1R might cause internalization and/or interruption of the signaling capacity of the other receptor. 6 These observations imply that AT1R and D1R may allosterically modulate each other.…”