摘要:

Abstract—The relative contribution of circulating versus tissue renin-angiotensin systems to the tissue expression of angiotensin peptides in the kidney remains unresolved. To address this issue, intrarenal and urinary levels of the peptide products of the renin-angiotensin system were assessed in a tissue angiotensin-converting enzyme knockout (tisACE−/−) mouse model. Systolic blood pressure was significantly lower (64.6±3.6 versus 81.4±4.5 mm Hg;P<0.02) and urinary volume was increased (7.25±0.86 versus 2.86±0.48 mL/d;P<0.001) intisACE−/−mice compared with wild-type mice. Intrarenal angiotensin II was 80% lower intisACE−/−mice compared with wild-type mice (5.17±0.60 versus 25.5±2.4 fmol/mg protein;P<0.001). Intrarenal angiotensin I levels also declined by a comparable extent (73%) in thetisACE−/−mice (P<0.01). Intrarenal angiotensin-(1–7) concentrations were similar between the strains, but the ratio of intrarenal angiotensin-(1–7) to angiotensin II and angiotensin I intisACE−/−mice increased 470% and 355%, respectively, compared with wild-type mice. Urinary excretion of angiotensin II and angiotensin-(1–7) were not different, but the excretion of angiotensin I increased 270% intisACE−/−mice (P<0.01). These studies suggest 2 potential mechanisms for the reduction of intrarenal angiotensin II intisACE−/−mice: (1) an attenuated capacity to form angiotensin II by renal angiotensin-converting enzyme and (2) significant depletion of its direct precursor angiotensin I in renal tissue. Sustained intrarenal levels of angiotensin-(1–7) may contribute to chronic hypotension and polyuria intisACE−/−mice, particularly in the context of depleted angiotensin II in the kidney.

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

摘要:

Abstract—There is uncertainty about the contribution of angiotensin-converting enzyme (ACE) to angiotensin II formation, with recent studies suggesting that non-ACE enzymes may be the predominant pathway of angiotensin II formation in kidney, heart, and lung. To investigate the role of ACE in angiotensin II formation, we measured angiotensin I and II levels in blood, kidney, and heart of 2 mouse genetic models (ACE.1 and ACE.4) of reduced somatic ACE gene expression and in blood, kidney, heart, lung, adrenal, and brain of mice administered the ACE inhibitor lisinopril. We also measured the levels of bradykinin (1-9) and its ACE metabolite bradykinin (1-7). Reduced ACE gene expression and ACE inhibition had similar effects on angiotensin and bradykinin peptide levels. Angiotensin II levels were reduced by 70% to 97% in blood, 92% to 99% in kidney, 93% to 99% in heart, 97% in lung, and 85% in adrenal and brain. The marked reductions in angiotensin II/angiotensin I ratio indicated that ACE was responsible for at least 90% of angiotensin I conversion to angiotensin II in blood, kidney, heart, lung, and brain, and at least 77% in adrenal. Blood bradykinin (1-9) levels were increased 6.4-fold to 8.4-fold. Heart bradykinin (1-9) levels were increased in ACE.4 mice and the bradykinin (1-7)/bradykinin (1-9) ratio was reduced in kidney and heart of ACE.4 mice and heart of lisinopril-treated mice. These studies demonstrate that ACE is the predominant pathway of angiotensin II formation in blood and tissues of mice and plays a major role in bradykinin (1-9) metabolism in blood and, to a lesser extent, in kidney and heart.

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

摘要:

Abstract—This study compared the expression of enzymes and transport and channel proteins involved in the regulation of sodium reabsorption in the kidney of Dahl salt-sensitive (DS) and salt-resistant Brown-Norway (BN) and consomic rats (SS.BN13), in which chromosome 13 from the BN rat has been introgressed into the DS genetic background. The expression of the Na+/K+/2Cl−(BSC-1) cotransporter, Na+/H+exchanger (NHE3), and Na+-K+-ATPase proteins were similar in the renal cortex of DS, BN, and SS.BN13 rats fed either a low-salt (0.1% NaCl) or a high-salt (8% NaCl) diet. The expression of the BSC-1 and the renal outer medullary K+channel (ROMK) were higher, whereas the expression of the cytochrome P4504A proteins responsible for the formation of 20-hydroxyeicosatetraenoic (20-HETE) was lower in the outer medulla of the kidney of DS than in BN or SS.BN13 rats fed either a low-salt or a high-salt diet. In addition, the renal formation and excretion of 20-HETE was lower in DS than in BN and SS.BN13 rats. These results suggest that overexpression of ROMK and BSC-1 in the thick ascending limb combined with a deficiency in renal formation of 20-HETE may predispose Dahl S rats fed a high-salt diet to Na+retention and hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

摘要:

Abstract—We have shown previously that increased extracellular osmolality stimulates expression and promoter activity of the type A natriuretic peptide receptor (NPR-A) gene in rat inner medullary collecting duct (IMCD) cells through a mechanism that involves activation of p38 mitogen-activated protein kinase (MAPK). The serum and glucocorticoid inducible kinase (Sgk) is thought to participate in the regulation of sodium handling in distal tubular segments. We sought to determine whether this kinase might be involved in the osmotic stimulation of NPR-A gene promoter activity. Exposure of cultured IMCD cells to an additional 75 mmol/L NaCl in culture media (final osmolality 475 mosm/kg) resulted in an ≈4-fold increase in Sgk1 protein levels after 7 hours. The Sgk1 induction was almost completely inhibited by the p38 MAPK inhibitor SB203580, indicating that NaCl activates Sgk1 through the p38 MAPK pathway. Transient transfection of a mouse Sgk1 expression vector along with a −1590 NPR-A luciferase reporter resulted in an ≈3-fold increment in reporter activity, which was significantly reduced by cotransfection with a kinase-dead Sgk1 mutant. The NaCl-dependent induction was partially blocked (≈40% inhibition) by cotransfection of the kinase-dead Sgk1 mutant. Neither Sgk1 nor the kinase-dead mutant had any effect on endothelial nitric oxide synthase (eNOS) promoter activity, and the Sgk1 mutant and 8-bromo-cyclic guanosine monophosphate were, to some degree, additive in reducing osmotically stimulated NPR-A promoter activity. Collectively, these data imply that Sgk1 operates over an eNOS-independent, p38 MAPK-dependent pathway in mediating osmotic induction of the NPR-A gene promoter.

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

摘要:

Abstract—Leukocyte adhesion to endothelial cells plays a key role in inflammatory processes associated with end-organ injury. Endothelin-1 (ET-1), which stimulates inflammatory processes, contributes to cardiovascular damage in deoxycorticosterone (DOCA)–salt hypertension. We investigated whether ETAreceptor blockade modulates in vivo leukocyte–endothelial cell interactions and expression of cell adhesion molecules (CAM) involved in these processes. DOCA–salt and control uninephrectomized rats were treated with the ETAantagonist BMS182874 (40 mg/kg per day) or vehicle. Analysis of CAMs expression by reverse transcription-polymerase chain reaction and immunohistochemistry showed increased cardiac platelet selectin (P-selectin), detected mainly in endothelial cells, and vascular cell adhesion molecule-1 (VCAM-1), but not intercellular adhesion molecule-1 (ICAM-1), in DOCA–salt rats. Cardiac expression of endothelial selectin (E-selectin) was decreased, whereas immunoreactivity to ED-1 and myeloperoxidase (MPO) activity, markers of macrophage and leukocyte infiltration, respectively, were increased in DOCA-salt. Leukocyte–endothelial cell interaction, functionally assessed in venules of internal spermatic fascia by intravital microscopy, was significantly altered in DOCA–salt rats as evidenced by increased leukocyte adhesion and decreased rolling. BMS182874 treatment normalized leukocyte–endothelium interactions, decreased cardiac VCAM-1 expression in DOCA and control groups, and had no effects on ICAM-1 expression. BMS182874 also increased E-selectin and abolished P-selectin expression in DOCA-salt, but not in control rats. The ETAantagonist reduced cardiac ED-1 content and MPO activity and prevented cardiac damage in DOCA–salt rats. These data indicate that ET-1 participates, via activation of ETAreceptors, in altered leukocyte–endothelial cell interactions in DOCA–salt rats, possibly by modulating expression of CAMs, and that the inflammatory status is associated with cardiac damage in mineralocorticoid hypertension.

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

摘要:

Abstract—A growing body of evidence has shown that Fas, a death receptor, mediates apoptosis-unrelated biological effects. Here, we report that Fas engagement with Fas ligand induced activation of Akt and upregulation of endothelial nitric oxide synthase expression without induction of apoptosis. In the presence of the phosphatidylinositol 3-kinase inhibitor wortmannin, Fas ligand, however, induced apoptosis instead of upregulation of endothelial nitric oxide synthase expression. In vivo, systolic blood pressure was slightly higher in mutant mice with decreased cell surface Fas expression (lprmice) compared with wild-type mice. In addition, chronic inhibition of nitric oxide synthesis byNG-nitro-l-arginine induced a progressive increase in the levels of blood pressure in wild-type mice, whereas no further increase in the levels of blood pressure was observed inlprmice. Furthermore, acetylcholine caused a lesser endothelium-dependent relaxation of the strips fromlprmice compared with wild-type mice, although the vasoconstrictor potency of phenylephrine was not different between the two groups. These findings indicate that Fas signaling may have a role in the regulation of endothelial function and blood pressure through modulating endothelial nitric oxide synthase expression in the Akt signal-dependent manner.

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

摘要:

Abstract—Increased expression of phosphoinositide 3-kinase (PI3-kinase) mediates elevated tone in the aorta from hypertensive deoxycorticosterone acetate (DOCA)-salt rats. In this article, we hypothesized that (1) alterations observed with respect to PI3-kinase observed in the aorta would also occur in mesenteric resistance arteries responsible for determining total peripheral resistance (TPR) and (2) p110&dgr; activity was increased and localized to vascular smooth muscle cells (VSMCs), and was responsible for the increase in spontaneous tone in aortae from DOCA-salt rats. Mesenteric resistance arteries and aorta were isolated from DOCA-salt (190±3 mm Hg) and sham (121±2 mm Hg) rats. Myograph experiments revealed LY294002 (20 &mgr;mol/L), a PI3-kinase inhibitor, significantly decreased tone in mesenteric resistance arteries from DOCA-salt rats as compared with sham (−49±12 mg versus −10±7 mg). Western analyses of resistance artery protein homogenate revealed p85&agr; and p110&dgr; subunit protein, with significantly elevated levels of p110&dgr; protein in the DOCA-salt compared with sham rats (0.30±0.07 versus 0.16±0.04% smooth muscle alpha-actin arbitrary units). Immunohistochemistry revealed p110&dgr;-specific staining in VSMCs, with more intense staining in aortae from DOCA-salt rats. Compared with aortae from sham, p110&dgr;-associated PI3-kinase activity was increased in DOCA-salt (158% of sham) and likely responsible for spontaneous tone because the p110&dgr; specific inhibitor IC87114 decreased spontaneous tone in a concentration-dependent manner. Collectively, these data further implicate the p110&dgr; isoform of PI3-kinase in arterial hyperresponsiveness in hypertension at the level of both large and small arteries.

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

摘要:

Abstract—The role of vascular smooth muscle inward rectifier K+(KIR) channels in the mechanisms underlying vasodilation is still unclear. The hypothesis that KIRchannels are involved in sodium nitroprusside (SNP)-induced dilation of rat-tail small arteries was tested. SNP relaxed tail small arteries with an EC50of 2.6×10−8mol/L. Endothelium removal did not attenuate this effect. Vessel pretreatment with hydroxocobalamin, a nitric oxide (NO) scavenger, but not with rhodanese and sodium thiosulfate, inactivators of cyanide (CN), abolished the SNP effect. Vessel pretreatment with 10−5mol/L Ba2+, a specific blocker of KIRchannels at micromolar concentrations, reduced the SNP effect. Low concentrations of K+dilated the vessels; this effect was attenuated largely after pretreatment with 3×10−5mol/L Ba2+. In freshly isolated smooth muscle cells, a barium-sensitive current was observed at potentials negative to the potassium equilibrium potential. Application of 10−4mol/L SNP increased the barium-sensitive current 1.79±0.23-fold at −100 mV and hyperpolarized the membrane potential by 8.6±0.5 mV. In tissue from freshly dissected vessels, transcripts for KIR2.1 and 2.2, but not for KIR2.3 and 2.4, were found. However, only KIR2.1 antibodies immunostained the tunica media of the vessel. These data suggest that vascular smooth muscle KIR2.1 channels are involved in the SNP-induced dilation of rat-tail small arteries.

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

摘要:

Abstract—Certain forms of coronary artery disease do not respond to treatment with Ca2+channel blockers, and a role for endothelin-1 (ET-1) in Ca2+antagonist-insensitive forms of coronary vasospasm has been suggested; however, the signaling mechanisms involved are unclear. We tested the hypothesis that a component of ET-1–induced coronary smooth muscle contraction is Ca2+antagonist-insensitive and involves activation of protein kinase C (PKC). Cell contraction was measured in smooth muscle cells isolated from porcine coronary artery, [Ca2+]iwas measured in fura-2 loaded cells, and the cytosolic and particulate fractions were examined for PKC activity and reactivity with isoform-specific PKC antibodies using Western blot analysis. In Hank’s solution (1 mmol/L Ca2+), ET-1 (10−7mol/L) caused a transient increase in [Ca2+]i(236±14 nmol/L) followed by a maintained increase in [Ca2+]i(184±8 nmol/L) and 35% cell contraction. The Ca2+channel blockers verapamil and diltiazem (10−6mol/L) abolished the maintained ET-1–induced [Ca2+]i, but only partially inhibited ET-1–induced cell contraction to 18%. The verapamil-insensitive component of ET-1 contraction was inhibited by the PKC inhibitors calphostin C and &egr;-PKCV1–2. ET-1 caused translocation of Ca2+-dependent &agr;-PKC and Ca2+-independent &egr;-PKC from the cytosolic to the particulate fraction that was inhibited by calphostin C. Verapamil abolished ET-1–induced translocation of &agr;-PKC, but not that of &egr;-PKC. Phorbol 12-myristate 13-acetate (10−6mol/L), a direct activator of PKC, caused 22% cell contraction, with no increase in [Ca2+]i, and translocation of &egr;-PKC that was inhibited by calphostin C, but not by verapamil. KCl (51 mmol/L), which stimulates Ca2+influx, caused 35% cell contraction and increase in [Ca2+]i(291±11 nmol/L) that were inhibited by verapamil, but not by calphostin C, and did not cause translocation of &agr;- or &egr;-PKC. In Ca2+-free (2 mmol/L EGTA) Hank’s solution, ET-1 caused 15% cell contraction, with no increase in [Ca2+]i, and translocation of &egr;-PKC that were inhibited by &egr;-PKC V1–2 inhibitory peptide. Thus, a significant component of ET-1–induced contraction of coronary smooth muscle is Ca2+antagonist-insensitive and involves activation and translocation of Ca2+-independent &egr;-PKC, and may represent a signaling mechanism of Ca2+antagonist-resistant forms of coronary vasospasm.

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:2004

数据来源: OVID