Active and passive liver microvascular responses from angiotensin, endothelin, norepinephrine, and vasopressin

2000 ◽  
Vol 279 (3) ◽  
pp. H1147-H1156 ◽  
Author(s):  
Carl F. Rothe ◽  
Roberto Maass-Moreno
Keyword(s):  
Control Period ◽  
Liver Volume ◽  
Vena Cava ◽  
Ang Ii ◽  
Liver Lobe ◽  
Arterial Blood ◽  
Total Hepatic Blood Flow ◽  
Constant Rate ◽  
Inferior Vena Cava Pressure ◽  
Capacitance Vessels

Vasoconstrictor agents may induce a decrease in hepatic vascular volume passively, by decreasing distending pressure, or actively, by stimulating contractile elements of capacitance vessels. Hepatic venular resistance was estimated in anesthetized rabbits from hepatic venular pressure (Pμhv; by servo-null micropipette), inferior vena cava pressure, and total hepatic blood flow (Fhv; by ultrasound flow probe). Changes in liver volume were estimated from measures of liver lobe thickness. Angiotensin (ANG) II, endothelin (ET)-1, norepinephrine (NE), and vasopressin (VP) were infused into the portal vein at a constant rate for 5 min. We conclude that ANG II and NE induced active constriction of hepatic capacitance vessels, because the liver lobe thickness decreased significantly even though Pμhv and portal venous distending pressure (Ppv) increased. All four agents increased splanchnic and hepatic venous resistances in similar proportions. With VP, Pμhv and Ppv decreased, but with ET-1, Pμhv and Ppv increased. However, lobe thickness was not significantly changed by either drug during the infusion compared with the 2-min control period. Thus VP and ET-1 have only minor effects on hepatic capacitance vessels. ET-1, at 0.04 μg · min−1 · kg body wt−1, caused an increase in systemic arterial blood pressure, but erythrocyte movement through the sinusoids in some animals stopped.

Hepatic venular resistance responses to norepinephrine, isoproterenol, adenosine, histamine, and ACh in rabbits

1998 ◽  
Vol 274 (3) ◽  
pp. H777-H785 ◽  
Author(s):  
Carl F. Rothe ◽  
Roberto Maass-Moreno
Keyword(s):  
Blood Flow ◽  
Portal Vein ◽  
Hepatic Blood Flow ◽  
Inferior Vena ◽  
Liver Volume ◽  
Liver Lobe ◽  
Inferior Vena Caval ◽  
Total Hepatic Blood Flow ◽  
Constant Rate ◽  
Increased Blood Flow

Changes in hepatic venous resistance were estimated in rabbits from the hepatic venular-inferior vena caval pressure gradient [servo-null micropipettes in 49 ± 15 (SD) μm vessels] and the total hepatic blood flow (ultrasound probe encircling the hepatic artery and the portal vein). Changes in liver volume, and thus vascular capacitance, were estimated from measures of the liver lobe thickness. Norepinephrine (NE), isoproterenol (Iso), adenosine (Ado), histamine (Hist), or acetylcholine (ACh) was infused into the portal vein at a constant rate for 5 min. NE, Hist, and Ado increased hepatic venular pressure, but only NE and Hist significantly increased hepatic venular resistance. NE reduced the liver thickness, but Hist and Ado caused engorgement. Hepatic blood flow was increased by NE and Ado and decreased by ACh. The influence of intraportal vein infusion of Iso on the liver vasculature, at doses similar to that of NE, was insignificant. We conclude that NE acted on all the hepatic microvasculature, increasing resistance and actively decreasing vascular volume. Hist passively induced engorgement by increasing outflow resistance, whereas the liver engorgement seen with Ado was passively related to the increased blood flow. ACh constricted the portal venules but did not change the liver volume.

Fetal placental vascular responses to prostacyclin after angiotensin II-induced vasoconstriction

1989 ◽  
Vol 257 (1) ◽  
pp. E102-E107
Author(s):  
V. M. Parisi ◽  
S. W. Walsh
Keyword(s):  
Blood Flow ◽  
Angiotensin Ii ◽  
Vascular Resistance ◽  
Control Period ◽  
Vena Cava ◽  
Ang Ii ◽  
Flow Measurements ◽  
Control Value ◽  
Blood Flow Measurements ◽  
Infusion Period

The vasodilator prostacyclin is produced by many fetal tissues and may serve to protect umbilical placental blood flow. We hypothesized that prostacyclin could reverse fetoplacental vasoconstriction produced by angiotensin II (ANG II). Studies were done in eight unanesthetized near-term ovine fetuses. After a control period, ANG II was infused into the fetal inferior vena cava at a rate of 0.5 microgram/min for 40 min. Twenty minutes after starting the ANG II infusion, an infusion of prostacyclin at a rate of 5 micrograms/min was added to the ANG II infusion. Blood flows were measured by the radioactive microsphere technique. Blood flow measurements were made during the control period, 20 min after starting the ANG II infusion, and 20 min after adding prostacyclin to the ANG II infusion. ANG II produced significant fetal hypertension and renal, intestinal, and placental vasoconstriction. Placental vascular resistance rose from 0.14 +/- 0.01 to 0.18 +/- 0.01 mmHg.min.kg fetal wt.ml-1 during the ANG II infusion period (P less than 0.05). The addition of prostacyclin to the ANG II infusion resulted in a return to control values for fetal blood pressure and renal and intestinal resistance. However, placental vasoconstriction was not reversed by addition of prostacyclin as placental vascular resistance remained significantly elevated over the control value (0.17 +/- 0.01 mmHg.min.kg fetal wt.ml-1). Although unchanged by ANG II infusion, fetal pH decreased significantly during the ANG II plus prostacyclin infusion period. We conclude that ANG II causes fetal hypertension and renal and intestinal vasoconstriction, which are reversed by prostacyclin.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic, hormonal, and drinking responses to reduced venous return in the dog

1982 ◽  
Vol 243 (3) ◽  
pp. R354-R362 ◽  
Author(s):  
T. N. Thrasher ◽  
L. C. Keil ◽  
D. J. Ramsay
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Water Intake ◽  
Venous Return ◽  
Control Level ◽  
Vena Cava ◽  
Plasma Renin ◽  
Ang Ii ◽  
Arterial Blood ◽  
Dog Plasma

The effect of an acute reduction in venous return, caused by reversible constriction of the thoracic vena cava, on drinking and secretion or arginine vasopressin (AVP) was examined in the dog. Plasma AVP levels rose immediately from a control level of 1.4 +/- 0.1 pg/ml (mean +/- SE) to a plateau ranging between 36 and 42 pg/ml during the first 30 min after constriction but declined to 12.6 +/- 4.2 pg/ml 2 h after constriction even though systemic arterial hypotension was maintained. Drinking occurred with a latency of 22 +/- 6 min and 13.2 +/- 1.8 ml H2O/kg was consumed during 2 h of vena caval constriction. Water intake was significantly correlated with the average reduction in blood pressure (r = 0.86; n = 8; P less than 0.01) but not with plasma renin activity. The role of angiotensin II (ANG II) in the drinking and secretion of AVP in response to decreased venous return was evaluated using the ANG II receptor blocker, saralasin, infused intravenously (iv) or intracerebroventricularly (icv). Intravenous, but not icv, infusion of saralasin during vena caval constriction reduced the ability of the dogs to maintain arterial blood pressure (P less than 0.05). However, neither iv nor icv saralasin significantly affected water intake or the rise in plasma AVP in response to vena caval constriction when compared to their respective controls. Taken together, these data show that angiotensin is important in the maintenance of systemic arterial blood pressure but is not essential for the rise in plasma AVP or drinking in response to an acute reduction in venous return. It is suggested that either arterial baroreceptors or "low-pressure" volume receptors or both mediate the drinking and AVP responses in the presence of central blockade of the effects of circulating angiotensin.

Hepatic effect of insulin in unanesthetized normal, diabetic, and adrenalectomized dogs

1961 ◽  
Vol 201 (5) ◽  
pp. 804-810 ◽  
Author(s):  
William C. Shoemaker ◽  
Peter J. Carruthers ◽  
Ina C. Powers ◽  
Howard M. Yanof
Keyword(s):  
Blood Flow ◽  
Femoral Vein ◽  
Vena Cava ◽  
Arterial Blood Flow ◽  
Constant Infusion ◽  
Hepatic Glycogen ◽  
Arterial Blood ◽  
Total Hepatic Blood Flow ◽  
Free Glucose ◽  
Glucose Output

Measurement of arterial, portal, and hepatic venous plasma glucose concentrations were made in unanesthetized dogs whose hepatic vessels were previously catheterized. Total hepatic blood flow was measured by a modified Bromsulphalein method and hepatic arterial blood flow by a trapezoidal wave electromagnetic blood flowmeter. Serial biopsies of the liver were obtained, also under unanesthetized conditions, for measurement of glycogen and free glucose. Various doses of glucagon-free insulin were given by a single, rapid, intravenous injection or by a constant infusion directly into the liver via portal vein and via femoral vein or vena cava. Insulin was administered in normal, in adrenalectomized, in depancreatized, and in depancreatized-adrenalectomized dogs. Under each of the conditions observed insulin produced no decrease in the hepatic glucose output. Moreover, no increased hepatic glycogen or free glucose concentrations were found in hepatic biopsies after insulin administration.

scholarly journals AT II Receptor Blockade and Renal Denervation: Different Interventions with Comparable Renal Effects?

2021 ◽  
pp. 1-11
Author(s):  
Kristina Rodionova ◽  
Martin Hindermann ◽  
Karl Hilgers ◽  
Christian Ott ◽  
Roland E. Schmieder ◽  
...  
Keyword(s):  
Body Weight ◽  
Volume Expansion ◽  
Neural Control ◽  
Renal Denervation ◽  
Urine Volume ◽  
Receptor Blockade ◽  
Ang Ii ◽  
Water Excretion ◽  
Arterial Blood ◽  
Renal Sympathetic

<b><i>Background:</i></b> Angiotensin II (Ang II) and the renal sympathetic nervous system exert a strong influence on renal sodium and water excretion. We tested the hypothesis that already low doses of an Ang II inhibitor (candesartan) will result in similar effects on tubular sodium and water reabsorption in congestive heart failure (CHF) as seen after renal denervation (DNX). <b><i>Methods:</i></b> Measurement of arterial blood pressure, heart rate (HR), renal sympathetic nerve activity (RSNA), glomerular filtration rate (GFR), renal plasma flow (RPF), urine volume, and urinary sodium. To assess neural control of volume homeostasis, 21 days after the induction of CHF via myocardial infarction rats underwent volume expansion (0.9% NaCL; 10% body weight) to decrease RSNA. CHF rat and controls with or without DNX or pretreated with the Ang II type-1 receptor antagonist candesartan (0.5 ug i.v.) were studied. <b><i>Results:</i></b> CHF rats excreted only 68 + 10.2% of the volume load (10% body weight) in 90 min. CHF rats pretreated with candesartan or after DNX excreted from 92 to 103% like controls. Decreases of RSNA induced by volume expansion were impaired in CHF rats but unaffected by candesartan pointing to an intrarenal drug effect. GFR and RPF were not significantly different in controls or CHF. <b><i>Conclusion:</i></b> The prominent function of increased RSNA – retaining salt and water – could no longer be observed after renal Ang II receptor blockade in CHF rats.

Gene expression reveals vulnerability to oxidative stress and interstitial fibrosis of renal outer medulla to nonhypertensive elevations of ANG II

2003 ◽  
Vol 284 (5) ◽  
pp. R1219-R1230 ◽  
Author(s):  
Baozhi Yuan ◽  
Mingyu Liang ◽  
Zhizhang Yang ◽  
Elizabeth Rute ◽  
Norman Taylor ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Western Blot ◽  
Renal Injury ◽  
Interstitial Fibrosis ◽  
Control Period ◽  
Renal Medulla ◽  
Differentially Expressed ◽  
Ang Ii ◽  
Outer Medulla ◽  
Renal Outer Medulla

The present study was designed to determine whether nonhypertensive elevations of plasma ANG II would modify the expression of genes involved in renal injury that could influence oxidative stress and extracellular matrix formation in the renal medulla using microarray, Northern, and Western blot techniques. Sprague-Dawley rats were infused intravenously with either ANG II (5 ng · kg−1 · min−1) or vehicle for 7 days ( n = 6/group). Mean arterial pressure averaged 110 ± 0.6 mmHg during the control period and 113 ± 0.4 mmHg after ANG II. The mRNA of 1,751 genes (∼80% of all currently known rat genes) that was differentially expressed (ANG II vs. saline) in renal outer and inner medulla was determined. The results of 12 hybridizations indicated that in response to ANG II, 11 genes were upregulated and 25 were downregulated in the outer medulla, while 11 were upregulated and 13 were downregulated in the inner medulla. These differentially expressed genes, most of which were not known previously to be affected by ANG II in the renal medulla, were found to group into eight physiological pathways known to influence renal injury and kidney function. Particularly, expression of several genes would be expected to increase oxidative stress and interstitial fibrosis in the outer medulla. Western blot analyses confirmed increased expression of transforming growth factor-β1 and collagen type IV proteins in the outer medulla. Results demonstrate that nonhypertensive elevations of plasma ANG II can significantly alter the expression of a variety of genes in the renal outer medulla and suggested the vulnerability of the renal outer medulla to the injurious effect of ANG II.

Electrophysiological evidence that systemic angiotensin influences rat area postrema neurons

1990 ◽  
Vol 258 (1) ◽  
pp. R70-R76 ◽  
Author(s):  
S. Papas ◽  
P. Smith ◽  
A. V. Ferguson
Keyword(s):  
Nucleus Tractus Solitarius ◽  
Area Postrema ◽  
Cell Types ◽  
Male Rats ◽  
Ang Ii ◽  
Adrenergic Agonist ◽  
Arterial Blood ◽  
Spontaneous Activities ◽  
Single Unit Recordings ◽  
Body Fluid Balance

Extracellular single-unit recordings from neurons in the area postrema (AP) and the nucleus tractus solitarius (NTS) in anesthetized male rats demonstrated that most cells in these regions have spontaneous activities of 5 Hz or less. Systemic angiotensin (ANG II) (50-500 ng) enhanced the activity of 55% of AP cells tested (n = 76), whereas 53% of tested NTS neurons (n = 62) were inhibited by ANG II. To determine whether these neurons were influenced specifically by circulating ANG II or by the accompanying increase in mean arterial blood pressure (BP), the effects of adrenergic agonists given intravenously on ANG II influenced neurons were also examined. Subsequently two cell types were characterized: cells responding to iv ANG II but not to the adrenergic agonist ("ANG II sensitive") and cells responding in a similar way to both agents ("BP sensitive"). Most ANG II-responsive neurons in the AP (53.5%) and the NTS (65%) were determined to be BP sensitive. These data demonstrate that ANG II influences the activity of AP neurons. In addition, there exists a second population of AP neurons apparently responsive to perturbations of the cardiovascular system. These studies further emphasize the potential roles of the AP in the regulation of body fluid balance.

scholarly journals Endoplasmic reticulum and oxidant stress mediate nuclear factor-κB activation in the subfornical organ during angiotensin II hypertension

2015 ◽  
Vol 308 (10) ◽  
pp. C803-C812 ◽  
Author(s):  
Colin N. Young ◽  
Anfei Li ◽  
Frederick N. Dong ◽  
Julie A. Horwath ◽  
Catharine G. Clark ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Angiotensin Ii ◽  
Er Stress ◽  
Bioluminescence Imaging ◽  
Nuclear Factor Κb ◽  
Nuclear Factor ◽  
Ang Ii ◽  
Arterial Blood

Endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) generation in the brain circumventricular subfornical organ (SFO) mediate the central hypertensive actions of Angiotensin II (ANG II). However, the downstream signaling events remain unclear. Here we tested the hypothesis that angiotensin type 1a receptors (AT1aR), ER stress, and ROS induce activation of the transcription factor nuclear factor-κB (NF-κB) during ANG II-dependent hypertension. To spatiotemporally track NF-κB activity in the SFO throughout the development of ANG II-dependent hypertension, we used SFO-targeted adenoviral delivery and longitudinal bioluminescence imaging in mice. During low-dose infusion of ANG II, bioluminescence imaging revealed a prehypertensive surge in NF-κB activity in the SFO at a time point prior to a significant rise in arterial blood pressure. SFO-targeted ablation of AT1aR, inhibition of ER stress, or adenoviral scavenging of ROS in the SFO prevented the ANG II-induced increase in SFO NF-κB. These findings highlight the utility of bioluminescence imaging to longitudinally track transcription factor activation during the development of ANG II-dependent hypertension and reveal an AT1aR-, ER stress-, and ROS-dependent prehypertensive surge in NF-κB activity in the SFO. Furthermore, the increase in NF-κB activity before a rise in arterial blood pressure suggests a causal role for SFO NF-κB in the development of ANG II-dependent hypertension.

General anesthesia and hepatic circulation

1987 ◽  
Vol 65 (8) ◽  
pp. 1762-1779 ◽  
Author(s):  
Simon Gelman
Keyword(s):  
Blood Flow ◽  
General Anesthesia ◽  
Surgical Procedures ◽  
Hepatic Blood Flow ◽  
Portal Blood Flow ◽  
Arterial Blood Flow ◽  
Hepatic Circulation ◽  
Arterial Blood ◽  
Total Hepatic Blood Flow ◽  
Circulatory Disturbances

This article describes hepatic circulatory disturbances associated with anesthesia and surgical intervention. The material is presented in three parts: part 1 describes the effects of general anesthetics on the hepatic circulation; part 2 deals with different factors related to surgical procedures and anesthesia; and part 3 analyzes the role of hepatic circulatory disturbances and hepatic oxygen deprivation in anesthesia-induced hepatotoxicity. The analysis of available data suggests that general anesthesia affects the splanchnic and hepatic circulation in various directions and to different degrees. The majority of anesthetics decreases portal blood flow in association with a decrease in cardiac output. However, hepatic arterial blood flow can be preserved, decreased, or increased. The increase in hepatic arterial blood flow, when it occurs, is usually not enough to compensate for a decrease in portal blood flow and therefore total hepatic blood flow is usually decreased during anesthesia. This decrease in total hepatic blood flow-has certain pharmacokinetic implications, namely a decrease in clearance of endogenous and exogenous substances with a high hepatic extraction ratio. On the other hand, a reduction in the hepatic oxygen supply might play a certain role in liver dysfunction occurring perioperatively. Surgical procedures–preparations combined with anesthesia have a very complex effect on the splanchnic and hepatic circulation. Within this complex, the surgical procedure–preparation plays the main role in developing circulatory disturbances, while anesthesia plays only a modifying role. Hepatic oxygen deprivation may play an important role in anesthesia-induced hepatotoxicity in different experimental models.

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