Renal cytochrome P-450-arachidonic acid metabolism: localization and hormonal regulation in SHR

1992 ◽  
Vol 262 (4) ◽  
pp. F591-F599 ◽  
Author(s):  
K. Omata ◽  
N. G. Abraham ◽  
M. L. Schwartzman
Keyword(s):  
Hormonal Regulation ◽  
Distribution Patterns ◽  
Arachidonic Acid Metabolism ◽  
Proximal Tubules ◽  
Ang Ii ◽  
Spontaneously Hypertensive ◽  
Nephron Segments ◽  
Wistar Kyoto ◽  
Cytochrome P 450 ◽  
Stimulation Of

Epoxygenase and omega- and omega-1-hydroxylases are the major cytochrome P-450-arachidonate (P-450-AA) metabolizing enzymes in renal tissues. We measured P-450-AA metabolism in single nephron segments and determined the tubular localization of this activity in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Formation of 20-hydroxyeicosatetraenoic acid (20-HETE), the product of AA omega-hydroxylase was specifically localized in the entire proximal tubules (S1, S2, and S3 segments), whereas formation of 19-HETE, the product of omega-1-hydroxylase and epoxyeicosatrienoic acids (EETs), products of AA epoxygenase, was demonstrable throughout the tubule. Although distribution patterns were similar in SHR and WKY, formation of 19- and 20-HETE in the proximal tubules was higher in SHR, whereas the formation of EETs was not different between the two strains. In the proximal tubules, angiotensin II (ANG II) significantly stimulated epoxygenase activity (EETs formation), whereas parathyroid hormone (PTH) and epidermal growth factor (EGF) had no effect on epoxygenase but significantly stimulated omega-hydroxylase activity (20-HETE formation). Because P-450-AA metabolites have a wide and contrasting spectrum of biological and renal effects, from vasodilation to vasoconstriction and from inhibition to stimulation of Na(+)-K(+)-adenosinetriphosphatase, their localization to the specific nephron segments and differential stimulation of their formation by ANG II, PTH, and EGF may contribute not only to renal hemodynamics and blood pressure regulation but also to the regulation of renal sodium and water balance.

Defective nitric oxide production impairs angiotensin II-induced Na-K-ATPase regulation in spontaneously hypertensive rats

2012 ◽  
Vol 302 (1) ◽  
pp. F47-F51 ◽  
Author(s):  
Apurva A. Javkhedkar ◽  
Mustafa F. Lokhandwala ◽  
Anees Ahmed Banday
Keyword(s):  
Nitric Oxide ◽  
Spontaneously Hypertensive Rats ◽  
Proximal Tubules ◽  
Ang Ii ◽  
Hypertensive Rats ◽  
High Concentration ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
Proximal Tubular ◽  
Stimulation Of

Angiotensin (ANG) II via ANG II type 1 receptors (AT1R) activates renal sodium transporters including Na-K-ATPase and regulates sodium homeostasis and blood pressure. It is reported that at a high concentration, ANG II either inhibits or fails to stimulate Na-K-ATPase. However, the mechanisms for these phenomena are not clear. Here, we identified the signaling molecules involved in regulation of renal proximal tubular Na-K-ATPase at high ANG II concentrations. Proximal tubules from spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats were incubated with low concentrations of ANG II (pM), which activated Na-K-ATPase in both the groups; however, the stimulation was more robust in SHR. A high concentration of ANG II (μM) failed to stimulate Na-K-ATPase in WKY rats. However, in SHR ANG II (μM) continued to stimulate Na-K-ATPase, which was sensitive to the AT1R antagonist candesartan. In the presence of NG-nitro-l-arginine methyl ester (l-NAME), a nitric oxide (NO) synthase (NOS) inhibitor, ANG II (μM) caused stimulation of Na-K-ATPase in proximal tubules of WKY rats while having no further stimulatory effect in SHR. ANG II (μM), via AT1R, increased proximal tubular NO levels in WKY rats but not in SHR. In SHR, NOS was uncoupled as incubation of proximal tubules with ANG II and l-arginine, a NOS substrate, caused superoxide generation only in SHR and not in WKY rats. The superoxide production in SHR was sensitive to l-NAME. There was exaggerated proximal tubular AT1R-G protein coupling and NAD(P)H oxidase activation in response to ANG II (μM) in proximal tubules of SHR compared with WKY rats. In SHR, inhibition of NADPH oxidase restored NOS coupling and ANG II-induced NO accumulation. In conclusion, at a high concentration ANG II (μM) activates renal NO signaling, which prevents stimulation of Na-K-ATPase in WKY rats. However, in SHR ANG II (μM) overstimulates NADPH oxidase, which impairs the NO system and leads to continued Na-K-ATPase activation.

scholarly journals The effects of angiotensin-(1–7) on the exchanger NHE3 and on [Ca2+]i in the proximal tubules of spontaneously hypertensive rats

2017 ◽  
Vol 313 (2) ◽  
pp. F450-F460 ◽  
Author(s):  
Regiane Cardoso Castelo-Branco ◽  
Deise C. A. Leite-Dellova ◽  
Fernanda Barrinha Fernandes ◽  
Gerhard Malnic ◽  
Margarida de Mello-Aires
Keyword(s):  
Plasma Level ◽  
Spontaneously Hypertensive Rats ◽  
High Plasma ◽  
Proximal Tubules ◽  
Ang Ii ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Wky Rats ◽  
High Plasma Level ◽  
Wistar Kyoto

The acute effects of angiotensin-1–7 [ANG-(1–7)] on the reabsorptive bicarbonate flow (J[Formula: see text]) were evaluated using stationary microperfusion in vivo in the proximal tubules of spontaneously hypertensive rats (SHR) and their normotensive controls, Wistar-Kyoto (WKY) rats, using a microelectrode sensitive to H+. In WKY rats, the control J[Formula: see text] was 2.40 ± 0.10 nmol·cm−2·s−1 ( n = 120); losartan (10−7 M) or A779 (10−6 M, a specific Mas antagonist), alone or in combination with losartan, decreased the J[Formula: see text]. ANG-(1–7) had biphasic effects on J[Formula: see text]: at 10−9 M, it inhibited, and at 10−6, it stimulated the flow. S3226 [10−6 M, a specific Na+-H+ exchanger 3 (NHE3) antagonist] decreased J[Formula: see text] and changed the stimulatory effect of ANG-(1–7) to an inhibitory one but did not alter the inhibitory action of ANG-(1–7). In SHR, the control J[Formula: see text] was 2.04 ± 0.13 nmol·cm−2·s−1 ( n = 56), and A779 and/or losartan reduced the flow. ANG-(1–7) at 10−9 M increased J[Formula: see text], and ANG-(1–7) at 10−6 M reduced it. The effects of A779, losartan, and S3226 on the J[Formula: see text] were similar to those found in WKY rats, which indicated that in SHR, the ANG-(1–7) action on the NHE3 was via Mas and ANG II type 1. The cytosolic calcium in the WKY or SHR rats was ~100 nM and was increased by ANG-(1–7) at 10−9 or 10−6 M. In hypertensive animals, a high plasma level of ANG-(1–7) inhibited NHE3 in the proximal tubule, which mitigated the hypertension caused by the high plasma level of ANG II.

Hormone responses of proximal Na(+)-H+ exchanger in spontaneously hypertensive rats

1991 ◽  
Vol 261 (3) ◽  
pp. F526-F536 ◽  
Author(s):  
F. A. Gesek ◽  
A. C. Schoolwerth
Keyword(s):  
Hormonal Regulation ◽  
Ang Ii ◽  
Acetoxymethyl Ester ◽  
Predisposing Factor ◽  
Adrenergic Agents ◽  
Spontaneously Hypertensive ◽  
Hormone Responses ◽  
Wistar Kyoto ◽  
22Na Uptake ◽  
Exchange Activity

Na(+)-H+ exchange activity is increased in hypertensive rat strains and could be a predisposing factor in the pathogenesis of essential hypertension. Previously we demonstrated that proximal nephron Na(+)-H+ exchange is stimulated by alpha-adrenergic agonists and angiotensin II (ANG II) and inhibited by parathyroid hormone (PTH) and dopamine (DA). To test the hypothesis that hormonal regulation of proximal nephron Na(+)-H+ exchange could differ with hypertension, alterations in Na(+)-H+ exchange were determined by 1) amiloride analogue-suppressible 22Na+ uptake and 2) change in intracellular pH (pHi) as monitored with the fluorescent probe 2',7'-bis(carboxyethyl)-5(6)carboxyfluorscein acetoxymethyl ester. Spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats had similar tail-cuff pressures at 4 wk, but SHR blood pressure was significantly elevated at 8 and 16 wk compared with WKY. No significant differences were observed between SHR and WKY basal ethylisopropyl amiloride-suppressible 22Na+ uptakes or rates of pHi change. alpha-Adrenergic agents and ANG II significantly increased (P less than 0.05) Na(+)-H+ exchange, but, in contrast, 8- and 16-wk-old SHR tubules lacked responsiveness to PTH (10(-8) M) and DA (10(-6) M) observed in WKY. A significant reduction (57–79%, P less than 0.05) in norepinephrine and ANG II stimulation was observed with 8- and 16-wk-old WKY tubules incubated in combination with PTH or DA, but only a 3–33% reduction was produced in 8- and 16-wk-old SHR tubules. PTH- and DA-stimulated adenosine 3',5'-cyclic monophosphate accumulation was significantly reduced in SHR compared with WKY tubules at 4 and 8 wk. It appears that proximal nephron Na(+)-H+ exchange activity is a balance between ANG II and NE activation and PTH and DA inhibition. The data suggest SHR proximal hormone responses are different from WKY and may alter the balance of net Na(+)-H+ exchange activity, possibly contributing to the development or maintenance of hypertension in the SHR.

Angiotensin II inhibits HCO 3 − absorption via a cytochromeP-450-dependent pathway in MTAL

1999 ◽  
Vol 276 (5) ◽  
pp. F726-F736 ◽  
Author(s):  
David W. Good ◽  
Thampi George ◽  
Donna H. Wang
Keyword(s):  
Tyrosine Kinase ◽  
Kinase Inhibitors ◽  
Extracellular Fluid ◽  
Arachidonic Acid Metabolism ◽  
Sodium Balance ◽  
Thick Ascending Limb ◽  
Ang Ii ◽  
Acid Base Balance ◽  
No Donor ◽  
Cytochrome P 450

The role of ANG II in the regulation of ion reabsorption by the renal thick ascending limb is poorly understood. Here, we demonstrate that ANG II (10−8 M in the bath) inhibits [Formula: see text] absorption by 40% in the isolated, perfused medullary thick ascending limb (MTAL) of the rat. The inhibition by ANG II was abolished by pretreatment with eicosatetraynoic acid (10 μM), a general inhibitor of arachidonic acid metabolism, or 17-octadecynoic acid (10 μM), a highly selective inhibitor of cytochrome P-450 pathways. Bath addition of 20-hydroxyeicosatetraenoic acid (20-HETE; 10−8 M), the major P-450 metabolite in the MTAL, inhibited [Formula: see text] absorption, whereas pretreatment with 20-HETE prevented the inhibition by ANG II. The addition of 15-HETE (10−8 M) to the bath had no effect on [Formula: see text]absorption. The inhibition of [Formula: see text]absorption by ANG II was reduced by >50% in the presence of the tyrosine kinase inhibitors genistein (7 μM) or herbimycin A (1 μM). We found no role for cAMP, protein kinase C, or NO in the inhibition by ANG II. However, addition of the exogenous NO donor S-nitroso- N-acetylpenicillamine (SNAP; 10 μM) or the NO synthase (NOS) substratel-arginine (1 mM) to the bath stimulated [Formula: see text] absorption by 35%, suggesting that NO directly regulates MTAL[Formula: see text] absorption. Addition of 10−11 to 10−10 M ANG II to the bath did not affect [Formula: see text] absorption. We conclude that ANG II inhibits [Formula: see text]absorption in the MTAL via a cytochrome P-450-dependent signaling pathway, most likely involving the production of 20-HETE. Tyrosine kinase pathways also appear to play a role in the ANG II-induced transport inhibition. The inhibition of [Formula: see text]absorption by ANG II in the MTAL may play a key role in the ability of the kidney to regulate sodium balance and extracellular fluid volume independently of acid-base balance.

Enhanced ANG II activity in anterior pituitary cell aggregates from hypertensive rats

1988 ◽  
Vol 255 (3) ◽  
pp. R407-R411
Author(s):  
W. Robberecht ◽  
C. Denef
Keyword(s):  
Defined Medium ◽  
Pituitary Cell ◽  
Pituitary Cells ◽  
Cell Aggregates ◽  
Ang Ii ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Wistar Kyoto ◽  
Dose Dependent ◽  
Perifusion System

Pituitary cell reaggregates from 14-day-old and adult spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) were cultured in serum-free, chemically defined medium supplemented with the thyroid hormone triiodothyronine and the glucocorticoid dexamethasone. After 1 wk in culture, aggregates were transferred into a perifusion system, and the effect of angiotensin II (ANG II) on prolactin (PRL) and growth hormone (GH) release was studied. In aggregates from adult SHR, ANG II displayed a significant and dose-dependent GH releasing activity, whereas a negligible effect or no effect was seen in aggregates from adult WKY. In contrast, no difference in the stimulation of PRL release by ANG II was found. To exclude the possibility that the enhanced GH responsiveness was secondary to longstanding hypertension, aggregates from animals in the prehypertensive stage were studied. Both the GH and PRL responses to ANG II were significantly higher in aggregates from 14-day-old SHR than in aggregates from 14-day-old WKY. These data indicate that abnormal GH and PRL responses to ANG II exist in pituitary cell aggregates from SHR long before hypertension develops. Because these differences were found in pituitary cells maintained in culture for 1 wk, they do not seem to be secondary to changes in brain regulation of pituitary function but rather are caused by factors intrinsic to the pituitary.

Interactions of cAMP-mediated vasodilators with angiotensin II in rat kidney during hypertension

1993 ◽  
Vol 265 (6) ◽  
pp. F845-F852 ◽  
Author(s):  
C. Chatziantoniou ◽  
X. Ruan ◽  
W. J. Arendshorst
Keyword(s):  
Angiotensin Ii ◽  
G Protein ◽  
Rat Kidney ◽  
Control Period ◽  
Ang Ii ◽  
Dibutyryl Camp ◽  
Renal Vasculature ◽  
Spontaneously Hypertensive ◽  
Electromagnetic Flowmetry ◽  
Wistar Kyoto

In previous studies [C. Chatziantoniou and W.J. Arendshorst. Am. J. Physiol. 263 (Renal Fluid Electrolyte Physiol. 32): F573-F580, 1992], we reported that vasodilator prostaglandins (PGs) are defective in buffering the angiotensin II (ANG II)-induced vasoconstriction in the renal vasculature of spontaneously hypertensive rats (SHR). The purpose of the present study was to determine whether this defect in SHR kidneys is specific to PGs or generalized to the action of vasodilators and to gain insight into which intracellular signal(s) mediates this abnormality. Renal blood flow (RBF; electromagnetic flowmetry) was measured in 7 wk-old anesthetized, euvolemic SHR and normotensive Wistar-Kyoto (WKY) rats pretreated with indomethacin to avoid interactions with endogenous PGs. ANG II (2 ng) was injected into the renal artery before and during continuous intrarenal infusion of fenoldopam [DA1 receptor agonist and G protein-dependent stimulator of adenosine 3',5'-cyclic monophosphate (cAMP)], forskolin (G protein-independent stimulator of cAMP), dibutyryl-cAMP (soluble cAMP), and acetylcholine (cGMP stimulator). Each vasodilator was infused at a low dose that did not affect baseline arterial pressure or RBF. In the control period, ANG II reduced RBF by 50% in both strains. Infusion of fenoldopam significantly blunted the ANG II-induced vasoconstriction in WKY, but not in SHR. In contrast, forskolin, dibutyryl-cAMP, and acetylcholine effectively buffered the vasoconstriction due to ANG II in both SHR and WKY. These results suggest that renal vasodilators acting through receptor binding to stimulate the cAMP signaling pathway are ineffective in counteracting the ANG II-induced vasoconstriction in SHR kidneys. (ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Effect of AT1 receptor blockade on hepatic redox status in SHR: possible relevance for endothelial function?

2003 ◽  
Vol 285 (3) ◽  
pp. R674-R681 ◽  
Author(s):  
Eva Cediel ◽  
David Sanz-Rosa ◽  
M. Pilar Oubiña ◽  
Natalia de las Heras ◽  
Francisco R. González Pacheco ◽  
...  
Keyword(s):  
Systolic Arterial Pressure ◽  
Redox System ◽  
Redox Status ◽  
Ang Ii ◽  
Spontaneously Hypertensive ◽  
Enos Mrna ◽  
Malonyl Dialdehyde ◽  
Wistar Kyoto ◽  
Oxide Synthase ◽  
Endothelial Nitric Oxide

The study investigated whether the amelioration of endothelial dysfunction by candesartan (2 mg·kg-1·day-1; 10 wk) in spontaneously hypertensive rats (SHR) was associated with modification of hepatic redox system. Systolic arterial pressure (SAP) was higher ( P < 0.05) in SHR than in Wistar-Kyoto rats (WKY) and was reduced ( P < 0.05) by candesartan in both strains. Acetylcholine (ACh) relaxations were smaller ( P < 0.05) and contractions induced by ACh + NG-nitro-l-arginine methyl ester (l-NAME) were greater ( P < 0.05) in SHR than in WKY. Treatment with candesartan enhanced ( P < 0.05) ACh relaxations in SHR and reduced ( P < 0.05) ACh + l-NAME contractions in both strains. Expression of aortic endothelial nitric oxide synthase (eNOS) mRNA was similar in WKY and SHR, and candesartan increased ( P < 0.05) it in both strains. Aortic mRNA expression of the subunit p22phox of NAD(P)H oxidase was higher ( P < 0.05) in SHR than in WKY. Treatment with candesartan reduced ( P < 0.05) p22phox expression only in SHR. Malonyl dialdehyde (MDA) levels were higher ( P < 0.05), and the ratio reduced/oxidized glutathione (GSH/GSSG) as well as glutathione peroxidase activity (GPx) were lower ( P < 0.05) in liver homogenates from SHR than from WKY. Candesartan reduced ( P < 0.05) MDA and increased ( P < 0.05) GSH/GSSG ratio without affecting GPx. Vessel, lumen, and media areas were bigger ( P < 0.05) in SHR than in WKY. Candesartan treatment reduced ( P < 0.05) media area in SHR without affecting vessel or lumen area. The results suggest that hypertension is not only associated with elevation of vascular superoxide anions but with alterations of the hepatic redox system, where ANG II is clearly involved. The results further support the key role of ANG II via AT1 receptors for the functional and structural vascular alterations produced by hypertension.

scholarly journals Phosphorylation of rat kidney Na-K pump at Ser938 is required for rapid angiotensin II-dependent stimulation of activity and trafficking in proximal tubule cells

2016 ◽  
Vol 310 (3) ◽  
pp. C227-C232 ◽  
Author(s):  
Katherine J. Massey ◽  
Quanwen Li ◽  
Noreen F. Rossi ◽  
Susan M. Keezer ◽  
Raymond R. Mattingly ◽  
...  
Keyword(s):  
Plasma Membranes ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Kidney Cells ◽  
Ang Ii ◽  
Wild Type ◽  
Stimulate Activity ◽  
Opossum Kidney ◽  
Opossum Kidney Cells ◽  
Stimulation Of

How angiotensin (ANG) II acutely stimulates the Na-K pump in proximal tubules is only partially understood, limiting insight into how ANG II increases blood pressure. First, we tested whether ANG II increases the number of pumps in plasma membranes of native rat proximal tubules under conditions of rapid activation. We found that exposure to 100 pM ANG II for 2 min, which was previously shown to increase affinity of the Na-K pump for Na and stimulate activity threefold, increased the amount of the Na-K pump in plasma membranes of native tubules by 33%. Second, we tested whether previously observed increases in phosphorylation of the Na-K pump at Ser938 were part of the stimulatory mechanism. These experiments were carried out in opossum kidney cells, cultured proximal tubules stably coexpressing the ANG type 1 (AT1) receptor, and either wild-type or a S938A mutant of rat kidney Na-K pump under conditions found by others to stimulate activity. We found that 10 min of incubation in 10 pM ANG II stimulated activity of wild-type pumps from 2.3 to 3.5 nmol K·mg protein−1·min−1 and increased the amount of the pump in the plasma membrane by 80% but had no effect on cells expressing the S938A mutant. We conclude that acute stimulation of Na-K pump activity in native rat proximal tubules includes increased trafficking to the plasma membrane and that phosphorylation at Ser938 is part of the mechanism by which ANG II directly stimulates activity and trafficking of the rat kidney Na-K pump in opossum kidney cells.

scholarly journals Perindoprilat Changes ANG (1-9) Production in Renal Arteries Isolated From Young Spontaneously Hypertensive Rats After ANG I Incubation

2016 ◽  
pp. 561-570
Author(s):  
P. P. WOŁKOW ◽  
B. BUJAK-GIŻYCKA ◽  
J. JAWIEŃ ◽  
R. OLSZANECKI ◽  
J. MADEJ ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Renal Artery ◽  
Spontaneously Hypertensive Rats ◽  
Renal Arteries ◽  
Ang Ii ◽  
Shr Rats ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive ◽  
Old Rats ◽  
Wistar Kyoto

We used mass spectrometry to quantitate production of angiotensinogen metabolites in renal artery of 3- and 7-month-old Wistar-Kyoto (WKY) and Spontaneously Hypertensive Rats (SHR). Tissue fragments were incubated for 15 min in oxygenated buffer, with added angiotensin I. Concentrations of angiotensins I (ANG I), II (ANG II), III (ANG III), IV (ANG IV), angiotensin (1-9) [ANG (1-9)], angiotensin (1-7) [ANG (1-7)], and angiotensin (1-5) [ANG (1-5)], excreted into the buffer during experiment, were measured using liquid chromatography-mass spectrometry (LC/MS) and expressed per mg of dry tissue. Effects of pretreatment with 10 μM perindoprilat on the production of ANG I metabolites were quantitated. Background production of any of ANG I metabolites differed neither between WKY and SHR rats nor between 3- and 7-month-old rats. Perindoprilat pretreatment of renal arteries resulted, as expected, in decrease of ANG II production. However, renal arteries of 7-month-old SHR rats were resistant to ACE inhibitor and did not change ANG II production in response to perindoprilat. In renal arteries, taken from 3-month-old rats, pretreated with perindoprilat, incubation with ANG I, resulted in the level of ANG (1-9) significantly higher in SHR than WKY rats. Our conclusion is that in SHR rats, sensitivity of renal artery ACE to perindoprilat inhibition changes with age.

Sign in / Sign up

Export Citation Format

Share Document