Altered vascular norepinephrine responses in portal hypertensive intestine: role of PKA and guanylate cyclase

1997 ◽  
Vol 272 (4) ◽  
pp. G831-G837 ◽  
Author(s):  
Z. Y. Wu ◽  
J. N. Benoit
Keyword(s):  
Blood Flow ◽  
Protein Kinase ◽  
Guanylate Cyclase ◽  
Sprague Dawley ◽  
Hypertensive Rats ◽  
Cyclic Monophosphate ◽  
Selective Blockade ◽  
Before And After ◽  
Ly 83583 ◽  
Arteriolar Diameter

The purpose of the present study was to determine whether selective blockade of adenosine 3',5'-cyclic monophosphate (cAMP)- or guanosine 3',5'-cyclic monophosphate (cGMP)-mediated events modulated norepinephrine responses in intestinal microvessels of normal and portal hypertensive rats. Vascular norepinephrine responses were evaluated before and after inhibition of cAMP-dependent protein kinase [protein kinase A(PKA)] with Rp-adenosine 3',5'-cyclic monophosphothioate (Rp-cAMPS) or guanylate cyclase with LY-83583. Male Sprague-Dawley rats were divided into two groups: those with portal hypertension by portal vein stenosis and normal controls. The small intestine was prepared for microcirculatory studies. Arteriolar diameter and erythrocyte velocity were monitored, and microvascular flow was calculated from velocity and diameter data. The preparation was challenged with incremental concentrations of norepinephrine before and after addition of Rp-cAMPS (50 microM) or LY-83583 (30 microM). Arteriolar diameter and blood flow were significantly elevated in portal hypertensive rats; norepinephrine responses were significantly depressed. LY-83583 did not alter arteriolar diameter, blood flow, or norepinephrine responsiveness in normal or portal hypertensive rats. Rp-cAMPS did not affect arteriolar diameter, blood flow, or norepinephrine responsiveness in normal rats. However, in portal hypertensive rats, Rp-cAMPS reduced blood flow by approximately 20% (P < 0.05) and completely restored vascular norepinephrine responses to normal. The results indicate that cAMP- but not cGMP-dependent events are primarily responsible for the loss of microvascular norepinephrine responsiveness in portal hypertensive intestine.

Contribution of adenosine to arteriolar autoregulation in striated muscle

1983 ◽  
Vol 244 (4) ◽  
pp. H567-H576 ◽  
Author(s):  
R. J. Morff ◽  
H. J. Granger
Keyword(s):  
Blood Flow ◽  
Striated Muscle ◽  
Perfusion Pressure ◽  
Cremaster Muscle ◽  
Sprague Dawley ◽  
Red Blood Cell Velocity ◽  
Myogenic Factors ◽  
Bath Medium ◽  
Arteriolar Diameter

The contribution of adenosine to blood flow autoregulation in striated muscle was evaluated by direct in vivo visualization of arterioles in the rat cremaster muscle. Male Sprague-Dawley rats were anesthetized with pentobarbital sodium, and the cremaster muscle was surgically exposed and maintained in a controlled tissue bath environment with pH 7.40, CO2 tension (PCO2) congruent to 40 mmHg, and O2 tension (PO2) at either a high (congruent to 70 mmHg) or a low (congruent to 10 mmHg) value. Local adenosine activity was blocked in some animals by the addition of theophylline (3 X 10(-5) M) to the bath medium. Individual second (2A)- and third (3A)-order arterioles were observed via closed-circuit television microscopy, and blood flow in each arteriole was calculated from simultaneous measurements of arteriolar diameter and red blood cell velocity. Perfusion pressure to the animal's hindquarters was altered by varying the degree of occlusion of the sacral aorta; arteriolar diameter, velocity, and blood flow responses were plotted as a function of the varying pressure. Both 2A and 3A arterioles exhibited vasodilation and substantial superregulation of blood flow (increased blood flow with decreased perfusion pressure) when bath PO2 was low and adenosine activity was not blocked. Addition of theophylline to the cremaster bath medium significantly reduced the dilation and abolished superregulation, although substantial autoregulation remained. When bath PO2 was high, the degree of arteriolar dilation and autoregulation was reduced compared with the low bath PO2 responses, and blocking adenosine activity had no effect on the responses. These results support the concept that changes in local adenosine levels are involved in the autoregulatory responses observed in the rat cremaster muscle and that the magnitude of adenosine's contribution is directly related to the degree of tissue hypoxia. However, blocking adenosine activity did not totally abolish autoregulation, suggesting that other metabolic and/or myogenic factors may also be contributing to blood flow regulation in this tissue.

Endogenous vasoconstrictor tone in intestine of normal and portal hypertensive rats

1993 ◽  
Vol 264 (1) ◽  
pp. H171-H177 ◽  
Author(s):  
T. Joh ◽  
D. N. Granger ◽  
J. N. Benoit
Keyword(s):  
Blood Flow ◽  
Portal Hypertension ◽  
Adrenergic Receptors ◽  
Adrenergic Blockade ◽  
Ang Ii ◽  
Hypertensive Rats ◽  
Alpha Adrenergic Receptors ◽  
Control Plasma ◽  
Arteriolar Diameter

The purpose of the present study was to determine the effects of endogenous norepinephrine, vasopressin (AVP), and angiotensin II (ANG II) on normal intestinal microvascular dimensions and to determine whether endogenous vasoconstrictor tone was altered in chronic portal hypertension. The intestine of normal and portal hypertensive rats was prepared for in vivo microscopic observation, and an arteriole (1A, 2A, or 3A) was selected for study. Arteriolar diameter and erythrocyte velocity were continuously monitored and used in the calculation of arteriolar blood flow. Once steady-state conditions were established, specific antagonists to alpha-adrenergic, AVP, or ANG II receptors were applied locally to remove the influences of each of these systems. In normal animals, blockade of alpha-adrenergic receptors produced a 1.3, 1.5, and 14.7% increase in the diameter of 1A, 2A, and 3A, respectively. AVP blockade in normal animals produced an 8.7, 1.6, and 1.5% increase in the diameter of 1A, 2A, and 3A, respectively; ANG II blockade only produced an increase in 3A diameter (5.8%). alpha-Adrenergic blockade produced a smaller increase in portal hypertensive 3A diameter (2.3%) compared with normal rats. AVP and ANG II blockade produced a significantly larger dilation of 3A (AVP, 4.8%) and 1A (ANG II, 3.8%), respectively, compared with control. Plasma AVP and ANG II levels were higher in portal hypertensive (AVP, 9.1 pg/ml; ANG II, 8.6 pg/ml) than in normal rats (AVP, 5.5 pg/ml; ANG II, 6.6 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Nitric oxide-induced microvascular permeability alterations: a regulatory role for cGMP

1993 ◽  
Vol 265 (6) ◽  
pp. H1909-H1915 ◽  
Author(s):  
P. Kubes
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Guanylate Cyclase ◽  
Microvascular Permeability ◽  
Independent Effect ◽  
No Donor ◽  
Cyclic Monophosphate ◽  
Protein Clearance ◽  
Guanylate Cyclase Activation ◽  
Permeability Alterations

This study evaluated the physiological effects of compounds that alter guanosine 3',5'-cyclic monophosphate (cGMP) on the increase in vascular protein clearance induced by nitric oxide (NO) synthesis inhibition in the feline small intestine. A lymphatic vessel draining the small bowel was cannulated; vascular protein clearance and intestinal blood flow were measured. N omega-nitro-L-arginine methyl ester (L-NAME), the NO inhibitor, was infused (0.5 mumol/min) into the superior mesenteric artery. Vascular protein clearance increased approximately 4.6-fold, whereas blood flow decreased to 50% of control. Elevation of cGMP by 1) cytosolic guanylate cyclase activation with a NO donor (SIN 1) or 2) a cGMP analogue, 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) completely prevented the rise in microvascular permeability associated with L-NAME. Moreover, these compounds reduced (almost 90%) baseline vascular protein clearance, whereas inhibition of cytosolic guanylate cyclase with methylene blue significantly increased this parameter. Atrial natriuretic factor (ANF) has been reported to increase tissue cGMP levels and microvascular permeability. In this study, ANF did indeed increase intestinal microvascular permeability however this occurred independent of changes in intestinal cGMP levels. These data support a role for cGMP associated with NO-induced microvascular permeability alterations and raise the possibility that ANF has a cGMP-independent effect on microvascular permeability within the intestine.

scholarly journals The Effects of Poststroke Captopril and Losartan Treatment on Cerebral Blood Flow Autoregulation in SHRsp with Hemorrhagic Stroke

2010 ◽  
Vol 31 (2) ◽  
pp. 476-485 ◽  
Author(s):  
John S Smeda ◽  
Noriko Daneshtalab
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Hemorrhagic Stroke ◽  
Hypertensive Rats ◽  
Lower Blood ◽  
Before And After ◽  
Doppler Techniques ◽  
Pressure Myograph ◽  
Captopril Treatment ◽  
Losartan Treatment

The ability of captopril and losartan treatment to restore cerebral blood flow (CBF) autoregulation after intracerebral hemorrhagic stroke (HS) was assessed in Kyoto–Wistar stroke-prone hypertensive rats (SHRsp). Laser Doppler techniques assessed CBF autoregulation in the middle cerebral artery (MCA) perfusion domain and a pressure myograph was used to measure pressure-dependent constriction (PDC) in isolated MCAs before and after stroke and after 13, 33, and 63 days of poststroke captopril or losartan treatment. The treatments did not lower blood pressure (BP) and equally suppressed plasma aldosterone after HS. The HS development was associated with the loss of CBF autoregulation, high CBF, increased CBF conductance to elevations in BP, and the loss of PDC in the MCAs. Both treatments restored these functions to prestroke levels within 13 days. The PDC and CBF autoregulation subsequently deteriorated after 63 days of captopril treatment while being maintained at prestroke levels over all durations of losartan treatment. The SHRsp subjected to 35 days of poststroke losartan treatment exhibited less blood–brain barrier (BBB) disruption and brain herniation than captopril-treated SHRsp. The superior ability of losartan to restore CBF autoregulation and myogenic function may have contributed to the more effective attenuation of cerebral damage after HS.

scholarly journals Increased activity and expression of Ca2+-dependent NOS in renal cortex of ANG II-infused hypertensive rats

1999 ◽  
Vol 277 (5) ◽  
pp. F797-F804 ◽  
Author(s):  
So Yeon Chin ◽  
Kailash N. Pandey ◽  
Shang-Jin Shi ◽  
Hiroyuki Kobori ◽  
Carol Moreno ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Renal Cortex ◽  
Renal Medulla ◽  
Ang Ii ◽  
Sprague Dawley ◽  
Hypertensive Rats ◽  
Differential Distribution ◽  
Cortical Blood Flow ◽  
Renal Cortical Blood Flow

We have previously demonstrated that nitric oxide (NO) exerts a greater modulatory influence on renal cortical blood flow in ANG II-infused hypertensive rats compared with normotensive rats. In the present study, we determined nitric oxide synthase (NOS) activities and protein levels in the renal cortex and medulla of normotensive and ANG II-infused hypertensive rats. Enzyme activity was determined by measuring the rate of formation ofl-[14C]citrulline froml-[14C]arginine. Western blot analysis was performed to determine the regional expression of endothelial (eNOS), neuronal (nNOS), and inducible (iNOS) isoforms in the renal cortex and medulla of control and ANG II-infused rats. Male Sprague-Dawley rats were prepared by the infusion of ANG II at a rate of 65 ng/min via osmotic minipumps implanted subcutaneously for 13 days and compared with sham-operated rats. Systolic arterial pressures were 127 ± 2 and 182 ± 3 mmHg in control ( n = 13) and ANG II-infused rats ( n = 13), respectively. The Ca2+-dependent NOS activity, expressed as picomoles of citrulline formed per minute per gram wet weight, was higher in the renal cortex of ANG II-infused rats (91 ± 11) than in control rats (42 ± 12). Likewise, both eNOS and nNOS were markedly elevated in the renal cortex of the ANG II-treated rats. In both groups of rats, Ca2+-dependent NOS activity was higher in the renal medulla than in the cortex; however, no differences in medullary NOS activity were observed between the groups. Also, no differences in medullary eNOS levels were observed between the groups; however, medullary nNOS was decreased by 45% in the ANG II-infused rats. For the Ca2+-independent NOS activities, the renal cortex exhibited a greater activity in the control rats (174 ± 23) than in ANG II-infused rats (101 ± 10). Similarly, cortical iNOS was greater by 47% in the control rats than in ANG II-treated rats. No differences in the activity were found for the renal medulla between the groups. There was no detectable signal for iNOS in the renal medulla for both groups. These data indicate that there is a differential distribution of NOS activity, with the Ca2+-dependent activity and protein expression higher in the renal cortex of ANG II-infused rats compared with control rats, and support the hypothesis that increased constitutive NOS activity exerts a protective effect in ANG II-induced hypertension to maintain adequate renal cortical blood flow.

Postpropranolol vasodilation in adrenalectomized glucocorticoid hypertensive rats

1987 ◽  
Vol 252 (6) ◽  
pp. H1243-H1248
Author(s):  
D. J. DiPette ◽  
J. F. Burris ◽  
A. Rogers ◽  
B. Waeber ◽  
H. R. Brunner
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Blood Pressure Lowering ◽  
Hypertensive Rats ◽  
Blood Pressure Lowering Effect ◽  
Lowering Effect ◽  
Before And After ◽  
Pressure Lowering ◽  
Regional Hemodynamics ◽  
Increased Blood Flow

Acute beta-adrenoreceptor blockade results in an enhanced blood pressure-lowering effect in glucocorticoid hypertensive rats in the absence of the adrenals. To evaluate the possible mechanism of this enhanced blood pressure-lowering effect, systemic and regional hemodynamics were determined by the radioactive microsphere technique before and after propranolol administration in bilaterally adrenalectomized (AX) and sham-operated (SH) glucocorticoid hypertensive rats. Propranolol decreased mean blood pressure (BP) and heart rate (HR) to a greater extent in the AX animals. In response to propranolol, cardiac output (CO) decreased equally in both the AX and SH animals. Regional vascular responses to propranolol were similar between the AX and SH animals, except in muscle. In muscle propranolol significantly decreased blood flow and increased resistance in the SH animals. In marked contrast, in the AX animals propranolol significantly increased blood flow and decreased vascular resistance. The results of this study show that in adrenalectomized glucocorticoid hypertensive rats, the enhanced BP lowering effect of acute beta-adrenoreceptor blockade is not mediated by changes in CO. Additionally, in glucocorticoid hypertensive rats acute beta-adrenoreceptor blockade causes selective vasodilation in skeletal muscle.

Superoxide anion inhibits cGMP-associated bovine pulmonary arterial relaxation

1990 ◽  
Vol 259 (4) ◽  
pp. H1056-H1062 ◽  
Author(s):  
P. D. Cherry ◽  
H. A. Omar ◽  
K. A. Farrell ◽  
J. S. Stuart ◽  
M. S. Wolin
Keyword(s):  
Guanylate Cyclase ◽  
Superoxide Anion ◽  
Pulmonary Arteries ◽  
Electron Donors ◽  
O2 Consumption ◽  
Cyclic Monophosphate ◽  
Arterial Relaxation ◽  
Diethyldithiocarbamic Acid ◽  
Pulmonary Arterial ◽  
Ly 83583

We have reported evidence that endothelium-independent relaxations of isolated bovine pulmonary arteries to H2O2 and to reoxygenation with 95% O2-5% CO2 after brief exposure to N2 (5% CO2) appear to be mediated by the activation of guanylate cyclase via H2O2 metabolism through catalase. Treatment of endothelium-removed pulmonary arteries with a potential guanylate cyclase-inhibitor, LY 83583, or with the inhibitor of the Zn+2, Cu+2-superoxide dismutase (SOD) diethyldithiocarbamic acid (DETCA), antagonized guanosine 3',5'-cyclic monophosphate (cGMP)-associated relaxation to H2O2, to reoxygenation and to glyceryl trinitrate, but not the adenosine 3',5'-cyclic monophosphate-associated relaxation to isoproterenol. Superoxide anion (O2-.) levels, detected by lucigenin-elicited chemiluminescence, were enhanced by LY 83583 or DETCA treatment of pulmonary arteries at ambient PO2. Chemiluminescence produced by LY 83583 was markedly potentiated by DETCA treatment, decreased at addition of exogenous SOD, and inhibited markedly by anoxia. LY 83583, but not DETCA, stimulated cyanide-insensitive O2 consumption, consistent with redox cycling of the compound independent of mitochondrial respiration. We propose that O2-. generated on the metabolism of LY 83583, or from cellular electron donors after SOD inhibition by DETCA, inhibits cGMP-mediated relaxations of pulmonary arteries.

Potentiation of Bradykinin by Angiotensin-(1-7) on Resistance Vessels of Hypertensive Rats, Studied in Vivo .

Hypertension ◽  
2000 ◽  
Vol 36 (suppl_1) ◽  
pp. 696-696
Author(s):  
Liliam Fernandes ◽  
Zuleica B Fortes ◽  
Dorothy Nigro ◽  
Regina Scivoletto ◽  
Robson A S Santos ◽  
...  
Keyword(s):  
Topical Application ◽  
Ace Inhibition ◽  
Pharmacological Effects ◽  
Hypertensive Rats ◽  
Specific Receptor ◽  
Resistance Vessels ◽  
Before And After ◽  
Arteriolar Diameter

P19 Objective: To verify the Angiotensin-(1-7) [Ang-(1-7)]-activity on Bradykinin (BK)-induced vasodilation in SHR mesenteric arterioles, in vivo-in situ. Methods: Arteriolar diameter was measured by intravital microscopy before and after topical application of BK(1pmol), Acetylcholine(ACh 1.6nmol), Sodium nitroprusside (SNP 38pmol) or Histamine (5.4nmol) in the absence or presence of Ang-(1-7) (100pmol). To investigate the Ang-(1-7)/BK interaction, treatments were employed through topical application of antagonists of BK (HOE140,100pmol), Ang-(1-7)(A779,100pmol)and potassium channel (tetraethylammoniun - TEA,90pmol), with an inhibitor of NOSynthase (L-NAME 10nmol) and after cyclooxygenase blockade (indomethacin 5mg/Kg or diclofenac 2.5mg/Kg). To evaluate the effect of ACE- and/or AT 1 blockade on Ang-(1-7)/BK interaction, rats were treated for 21 days with enalapril, quinapril (10mg/Kg), losartan (15mg/Kg) or enalapril + losartan (10 and 15 mg/Kg, respectively). In those enalapril-treated rats the effect of BK (1pmol) was also analysed in the presence of A779 (100pmol). Results: BK-induced vasodilation, but not ACh, SNP or Histamine responses, was increased in the presence of Ang-(1-7) (4.96±0.7% vs 9.07±1.0% * ).This interaction was abolished by HOE (1.11±0.8% * ), A779 (5.13±0.6% * ), TEA (3.37±0.5% * ), indomethacin (1.73±0.4% * )and diclofenac (3.63±0.5% * ), whereas L-NAME did not modify the Ang-(1-7)-potentiating activity. The BK-potentiation by Ang-(1-7) was also observed after enalapril (10.57±0.5% * ), quinapril (8.9±0.7% * ), losartan (9.93±1.2% * ) and enalapril + losartan (10.59±0.5% * ). Enalapril increased the BK-vasodilation(8.21±0.7% * ), but this effect was reversed in the presence of A779 (4.27±0.5% * ). * p≤0.05 Conclusion: In the SHR microcirculation Ang-(1-7) potentiates BK through a specific receptor, probably releasing prostaglandins and EDHF. Our results indicate that the BK-potentiation by Ang-(1-7) may occur endogenously and contribute to the pharmacological effects of ACE inhibition. HOE 140 and Quinapril were gifts from HOECHST and Warner Lambert, respectively.

Renoprotective effects of nitric oxide in angiotensin II-induced hypertension in the rat

1998 ◽  
Vol 274 (5) ◽  
pp. F876-F882 ◽  
Author(s):  
So Yeon Chin ◽  
Chi-Tarng Wang ◽  
Dewan S. A. Majid ◽  
L. Gabriel Navar
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Fractional Excretion ◽  
Urinary Sodium Excretion ◽  
Ang Ii ◽  
Sprague Dawley ◽  
Hypertensive Rats ◽  
Absolute Increase ◽  
Sprague Dawley Rats ◽  
Fractional Excretion Of Sodium

Experiments were performed in anesthetized male Sprague-Dawley rats to determine whether increased nitric oxide (NO) activity during the development of hypertension exerts a protective effect on renal cortical blood flow (CBF) and medullary blood flow (MBF). The effects of acute NO synthase inhibition on renal function and on CBF and MBF, measured by laser-Doppler flow probes, were evaluated in control and ANG II-infused hypertensive rats, prepared by the infusion of ANG II at a rate of 65 ng/min via osmotic minipumps implanted subcutaneously for 13 days. In normotensive rats ( n = 8), intravenous infusion of N ω-nitro-l-arginine (NLA; 20 μg ⋅ 100 g−1 ⋅ min−1) decreased CBF by 21 ± 4% and MBF by 49 ± 8% and increased blood pressure from 118 ± 1 to 140 ± 2 mmHg. In ANG II-infused rats ( n = 7), CBF and MBF decreased by 46 ± 5% and 25 ± 6%, respectively, during infusion of NLA. Arterial pressure increased from 160 ± 5 to 197 ± 7 mmHg, which was a greater absolute increase than in normotensive controls. Basal renal blood flow (RBF), estimated from p-aminohippurate clearance and hematocrit, was similar in both the control (6.0 ± 0.5 ml ⋅ min−1 ⋅ g−1) and hypertensive (6.0 ± 0.6 ml ⋅ min−1 ⋅ g−1) rats. However, NLA-induced reductions in RBF averaged 60 ± 5% in the hypertensive rats, compared with 31 ± 9% observed in control rats. GFR in control (0.97 ± 0.03 ml ⋅ min−1 ⋅ g−1) and hypertensive rats (0.78 ± 0.12 ml ⋅ min−1 ⋅ g−1) decreased to a similar extent during the first 30-min period of NLA infusion. GFR returned toward control levels in control rats; in contrast, GFR remained significantly decreased in the ANG II-infused rats (0.58 ± 0.11 ml ⋅ min−1 ⋅ g−1). Basal urinary sodium excretion (0.2 ± 0.08 μeq ⋅ min−1 ⋅ g−1), fractional excretion of sodium (0.3 ± 0.13%), and urine flow (4.9 ± 0.39 μl ⋅ min−1 ⋅ g−1) in hypertensive rats did not increase significantly after NLA treatment as occurred in normotensive controls. These data suggest that a compensatory increase in nitric oxide activity partially counteracts the vasoconstrictor influence of elevated ANG II levels to regulate renal hemodynamics and maintain cortical perfusion in the renal circulation.

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