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K A Duggan

Publications and source records attributed to K A Duggan.

At least 19 recordsLinked to original sources
PubMed2001

Effects of nitric oxide synthase inhibition on angiotensin receptors and metabolism in the pregnant hypertensive rat.

Endothelial dysfunction and a consequent decrease in nitric oxide production have been implicated in the pathogenesis of pre-eclampsia. A prominent feature of the pre-eclamptic syndrome is a loss of the pregnancy-induced refractoriness to infused pressor agents, such as angiotensin. In this study, we sought to determine whether a decrease in nitric oxide production might be linked via changes in angiotensin II receptors and angiotensin II metabolism to changes in pressor sensitivity to infused angiotensin II. Pregnant and non-pregnant spontaneously hypertensive rats (SHRs) were randomly allocated to receive 5 mg x kg(-1) x day(-1) N(G)-nitro-L-arginine methyl ester (L-NAME) in the drinking water or drinking water alone from days 7 to 14 of gestation. Steady-state metabolic clearance studies of angiotensin II were then performed, or tissues were harvested for angiotensin II receptor studies. Treatment with L-NAME caused an increase in systolic pressure (P<0.001) in both pregnant and non-pregnant rats, while urinary protein excretion increased only in the pregnant SHRs (P<0.001). Plasma angiotensin II levels were significantly increased in the L-NAME-treated SHRs compared with controls (non-pregnant, P<0.0005; pregnant, P<0.01). The metabolic clearance rate of angiotensin II was decreased by L-NAME treatment in non-pregnant SHRs (P<0.05), but was increased by L-NAME treatment in the pregnant rats (P<0.01). In the aorta, the angiotensin II receptor number increased after treatment with L-NAME in both non-pregnant (P<0.0005) and pregnant (P<0.05) SHRs, and the dissociation constant increased in the non-pregnant SHRs (P<0.005). Thus treatment of SHRs with L-NAME increased blood pressure, as well as the circulating angiotensin II concentration and vascular angiotensin II receptor expression. However, treatment with L-NAME did not affect pressor sensitivity to infused angiotensin II. We conclude, therefore, that although a decrease in nitric oxide production is associated with changes in angiotensin II concentrations and receptor numbers, it does not induce changes in pressor sensitivity to infused angiotensin II in the SHR.

Analysis of Variance↗
PubMed2000

Factors regulating renal angiotensin-converting enzyme activity in the rat.

Changes in angiotensin-converting enzyme (ACE) activity appear to be important in mediating the natriuresis which ensues after administration of an oral or gastric sodium load. In this study, we sought to determine the time course of the changes in ACE activity in the kidney which occur after sodium ingestion. In addition, we sought to investigate mechanisms which might underlie these changes. Angiotensin-converting enzyme activity was measured by generation of histidyl-leucine in homogenates of kidneys harvested at varying time-points after gastric sodium administration. The effects of intravenous sodium loading, solution osmolality and of changes in renal nerve activity were also investigated. Intragastric instillation of both the sodium-containing solution and its iso-osmotic urea control solution resulted in significant increases in renal ACE activity (NaCl: P < 0.0005; Urea: P < 0.01). The increase in renal ACE activity after gastric sodium loading was more prolonged than after the urea control (P < 0.025, NaCl vs. urea at 90 min). This prolonged increase in renal ACE activity appeared to reflect a response to absorbed sodium as intravenous sodium administration caused a significant increase in renal ACE activity at 90 min (P < 0.0005). In contrast to these stimuli which increased renal ACE activity, renal denervation caused a significant decrease in ACE activity in the kidney (P < 0.05). We conclude that gastric sodium loading increases renal ACE activity. This effect appears to be due initially to a response to an increase in gastric lumenal osmolality and later to absorbed sodium. These changes in renal ACE activity are not mediated by a decrease in renal nerve activity.

Animals↗
PubMed2000

Modulation of the intrahepatic renin-angiotensin system after stimulation of the gastric sodium monitor in the rat.

Changes in the rate of formation of angiotensin II (ANG II) participate in mediating the natriuresis that occurs in direct response to a gastric sodium stimulus (upper-gut sodium monitor). As this natriuresis is also dependent on intrahepatic events, we investigated whether changes in hepatic and plasma angiotensinogen levels and hepatic angiotensin-converting enzyme (ACE) activity might explain the decrease in ANG II synthesis. Male Sprague-Dawley rats, equilibrated on a low-sodium diet, were anaesthetized and received a sodium load of 1.5 mmol/kg (using 3 x normal saline) either intragastrically or intravenously. Blood and livers were sampled before and at various times after sodium administration. ACE activity in serum and tissues was determined by generation of histidyl-leucine. Angiotensinogen was determined by radioimmunoassay of angiotensin I generated by incubation in the presence of exogenous renin. Plasma angiotensinogen had decreased significantly by 15 min after sodium administration (P<0.005), while hepatic angiotensinogen was also decreased significantly from 30 min after the sodium load (P<0.01). Hepatic ACE activity decreased in response to sodium (P<0.005) from 30 min. We conclude that stimulation of the gastric sodium monitor regulates angiotensinogen synthesis and secretion by the liver, as well as hepatic ACE activity.

Angiotensin I↗
PubMed1998

Effects of enalapril on vasoactive intestinal peptide metabolism and tissue levels.

Angiotensin converting enzyme inhibitor therapy results in an increase in cardiac output without an increase in heart rate suggesting a positive inotropic effect. This cannot be explained by changes in angiotensin II and bradykinin concentrations. Angiotensin converting enzyme may also metabolise vasoactive intestinal peptide (VIP), a vasodilator and positive inotrope whose concentration in the heart declines in heart failure. We sought to determine whether changes in plasma VIP or its metabolism might explain the positive inotropic effect of angiotensin converting enzyme inhibitors. We also measured VIP in the heart to determine whether a local increase in VIP might explain this effect. Male Sprague-Dawley rats were randomised to control and enalapril groups (2 mg kg(-1) day(-1)). After 7 days, rats were anaesthetised and underwent metabolic clearance studies for VIP or had hearts, lungs and kidneys removed and snap frozen. VIP concentrations in plasma, infusate and tissue extracts were measured by radioimmunoassay. Plasma concentrations of VIP were unchanged by treatment with enalapril (control: 7.7 +/- 0.8 pmol l(-1); enalapril: 7.9 +/- 0.8 pmol l(-1) ), while the metabolic clearance rate of) VIP increased significantly (control: 10.4 +/- 1.4 ml min(-1) 100 g(-1); enalapril: 17.3 +/- 1.6 ml min(-1) 100 g(-1); p < 0.005). Secretion rate) also increased in enalapril treated rats (139.1 +/- 25.0 pmol min(-1) 100 g(-1) compared with controls (96.3 +/- 13.4 pmol min (-1) 100 g(-1); P< 0.01). VIP in the heart increased after enalapril (control: 208.4 +/- 39.0 pmol g (-1); enalapril: 928.9 +/- 123.6 fmol g(-1); P < 0.0005). Angiotensin converting enzyme inhibition increases the metabolism of VIP. However, the significant increase in the myocardial concentration of VIP may contribute to the beneficial haemodynamic inotrope effects of angiotensin converting enzyme inhibitors.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

Renoprotective differences between perindopril and enalapril in the diabetic hypertensive rat do not reflect glomerular angiotensin-converting enzyme activity.

1. The various angiotensin-converting enzyme inhibitors have structural differences which affect their affinities for the catalytic sites on converting enzyme. We postulated that such differences might result in differences in renoprotective efficacy. We investigated this in the diabetic spontaneous hypertensive rat. We also investigated whether these differences might reflect variations in glomerular or plasma angiotensin-converting enzyme activity. 2. One week after induction of diabetes, rats were started on antihypertensive therapy: enalapril, 10 mg.day-1.kg-1, or perindopril, 4 mg.day-1.kg-1, in the drinking water. After 3 months, the rats were killed, blood samples were taken and tissues were harvested. Angiotensin-converting enzyme activity in isolated glomeruli and plasma was measured by fluorimetric assay. Glomerular protein content was also determined. 3. Urinary protein excretion was significantly lower in perindopril-treated rats than in either controls (P < 0.0005) or enalapril-treated rats (P < 0.05). Glomerular protein content was also lower in perindopril-treated rats (P < 0.05 versus enalapril; P < 0.005 versus control). There was no difference in glomerular angiotensin-converting enzyme activity between the two inhibitors although both were lower than control values (enalapril P < 0.025; perindopril P < 0.025). Plasma angiotensin-converting enzyme activity was significantly lower in the perindopril group than in either control (P < 0.005) or the enalapril group (P < 0.01). 4. We conclude that in the spontaneous hypertensive rat with streptozotocin-induced diabetes, perindopril is more effective than enalapril in reducing proteinuria and glomerular protein accumulation. This difference does not result from differences in glomerular-converting enzyme activity.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

Mechanisms underlying the decrease in circulating angiotensin II concentration after sodium loading.

1. Acute sodium loading causes a rapid decrease in the circulating concentration of angiotensin II (AngII), which is apparent from 5 min after sodium administration. This could result from an increase in AngII catabolism and/or a decrease in AngII synthesis/secretion. However, the major determinant of AngII synthesis is thought to be a change in plasma renin activity, which occurs over a longer time frame (15 min). 2. To investigate the mechanisms underlying the rapid decrease in plasma AngII engendered by sodium administration, we performed metabolic clearance studies in male New Zealand white rabbits before and after a hypertonic sodium load of 1.5 mmol/kg as 0.513 mol/L saline i.v. bolus. 3. The metabolic clearance rate of AngII increased significantly from 42.2 +/- 9.0 mL/min per kg before sodium to 110.8 +/- 33.7 mL/min per kg after sodium administration (P < 0.05). The calculated or theoretical secretion rate decreased from 1470.7 +/- 404.2 to 573.5 +/- 139.5 fmol/min per kg (P < 0.025) in response to sodium. 4. We conclude that an increase in AngII metabolism and a decrease in synthesis/secretion contribute to the reduction in circulating AngII, which occurs in the first 60-90 min after sodium loading.

Angiotensin II↗
PubMed1997

Stimulation of the gastric sodium monitor reduces hepatic angiotensin-converting enzyme activity.

1. The natriuresis engendered by stimulation of the gastric sodium monitor is mediated in part by a decrease in the circulating concentration of angiotensin II (AngII). This decrease is due to decrease in synthesis rather than to an increase in metabolism. We investigated the role of changes in plasma and hepatic angiotensin-converting enzyme (ACE) activity in this decrease in AngII synthesis. 2. Male Sprague-Dawley rats were equilibrated on a low-sodium diet for 7 days. On the day of experiment, rats were anaesthetized and received either a sodium load of 1.5 mmol/kg as 3 mol/L saline or an equivalent volume of an iso-osmotic urea solution by direct gastric puncture. Blood was sampled and livers were harvested at 0 and 30 min after sodium or urea administration. Angiotensin-converting enzyme was measured in serum and tissue homogenates by generation of histidyl-leucine. 3. In the liver, ACE activity decreased from control after both sodium (P < 0.005) and urea (P < 0.025) administration. The decrease was greater in the group that received saline compared with rats that received urea (P < 0.05). Serum ACE decreased in response to urea (P < 0.025) but not sodium administration. 4. We conclude that stimulation of the gastric sodium monitor results in a decrease in ACE activity in the liver. This decrease in ACE activity may be contributory to the decrease in AngII synthesis.

Angiotensin II↗
PubMed1997

Acute but not chronic angiotensin-converting enzyme inhibition induces enzyme synthesis in the glomerulus of the spontaneously hypertensive rat.

1. Treatment with angiotensin-converting enzyme (ACE) inhibitors slows the rate of progression of nephropathy in the spontaneously hypertensive rat (SHR) with streptozotocin-induced diabetes. Paradoxically, however, chronic ACE inhibitor therapy has been reported to be associated with induction of ACE in the plasma. We sought to determine whether induction also occurred in the glomerulus. 2. Seven days after induction of diabetes rats were randomized to receive perindopril (4 mg/kg per day) in the drinking water or water alone. Blood glucoses were maintained 6-10 mmol/L by daily ultralente insulin. Rats were killed after 1 and 12 weeks of ACE inhibitor therapy and the kidneys were harvested. Angiotensin-converting enzyme activity was determined in isolated glomeruli before and after removal of perindopril and reconstitution with zinc sulphate. 3. After 1 week of ACE inhibitor therapy, glomerular ACE was significantly greater after removal of perindopril than either before its removal (P < 0.025) or in the untreated controls (P < 0.025). After 12 weeks of therapy, ACE activity was significantly lower in the perindopril-treated group than in the untreated controls (P < 0.025). There was no increase in ACE activity following removal of perindopril. 4. These studies suggest that short-term ACE inhibition is associated with induction of ACE in the glomerulus. However, there was no increase in ACE activity after removal of perindopril, suggesting that induction of synthesis of this enzyme in the glomerulus does not occur during chronic ACE inhibition.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Stimulation of gastric osmoreceptors but not the sodium monitor increases renal angiotensin-converting enzyme activity.

1. Stimulation of the gastric sodium monitor has been reported to cause a decrease in renal nerve activity and also a decrease in plasma renin activity in renal venous blood. This suggests that changes in sympathetic nerve activity and in the intrarenal renin-angiotensin system may mediate the natriuresis that occurs following gastric sodium administration. In the present study we sought to determine whether gastric sodium administration also modulates angiotensin-converting enzyme (ACE) activity in the kidney. 2. Male Sprague-Dawley rats were equilibrated on a low-sodium (0.008%) diet for 7 days. On the day of the experiment, rats were anaesthetized and kidneys were harvested and immediately snap frozen at 0 and 60 min after intragastric administration of a saline load (1.5 mmol/kg as 3 mol/L saline) or an equivalent volume of iso-osmotic urea (5.95%). Angiotensin-converting enzyme activity was determined by incubation of kidney homogenates with hippuryl-histidyl-leucine and fluorometric assay of the histidyl-leucine generated. 3. Angiotensin-converting enzyme activity in the kidney increased in response to the intragastric administration of both sodium chloride and urea. Angiotensin-converting enzyme activity increased significantly from control levels (189.9 +/- 24.3 nmol/min per g protein) by 60 min in both NaCl-and urea-treated groups (492.3 +/- 27.3 and 468.6 +/- 28.7 nmol/min per g protein, respectively; P < 0.0005). 4. We conclude that instillation of sodium chloride or isoosmotic urea into the stomach increase ACE activity in the kidney. The results of the present study suggest that this effect is due to changes in osmolality rather than stimulation of the gastric sodium monitor.

Animals↗
PubMed1997

Evidence for direct interaction of ketamine with alpha 1- and beta 2-adrenoceptors.

1. Ketamine has a number of effects that suggest that it may interact with alpha- and beta-adrenoceptors. To date, the experimental evidence for this has been indirect and has been based on physiological studies using competitive blocking agents. In the present study we sought to determine from receptor binding studies whether ketamine binds directly to alpha- and beta-adrenoceptors. 2. Membrane preparations of alpha 1- and beta 2-adrenergic binding sites were obtained from urinary bladder and urethrae of sheep. These binding sites were characterized by saturation analyses using [3H]-prazosin for alpha 1-adrenoceptor binding sites and [125I]-cyanopindolol (CYP) for the beta 2-adrenoceptor binding sites. The receptors were further characterized by displacement studies using selective and non-selective antagonists. 3. Studies in which ketamine was used to displace [3H]-prazosin revealed a Kd of 3.40 +/- 1.23 x 10(-3) mol/L for ketamine binding to alpha 1-adrenoceptors. Displacement studies of [125I]-CYP by ketamine showed a Kd of 0.35 +/- 0.03 x 10(-3) mol/L for ketamine binding to beta 2-adrenoceptors. 4. We conclude that ketamine interacts directly with both alpha 1- and beta 2-adrenoceptors and that such interactions probably explain the reported effects of this agent on the vasculature and the bronchial tree.

Adrenergic alpha-Antagonists↗
PubMed1996

Angiotensin-converting enzyme inhibition with enalapril increases the cardiac concentration of vasoactive intestinal peptide.

In patients with congestive cardiac failure, treatment with ACE inhibitors results in peripheral vasodilatation and an increase in cardiac output without an increase in heart rate, which suggests a positive inotropic effect. This cannot be explained by the changes in angiotensin II and bradykinin concentrations that occur. It has been suggested that ACE also metabolizes VIP, which is a positive inotrope. As VIP is synthetized by the heart and acts locally to increase cardiac output, we postulated that ACE inhibition would increase the myocardial concentration of VIP. Male Sprague-Dawley rats received enalapril (2 mg/kg/day) in the drinking water or no therapy for seven days. On day seven they were anaesthetized and blood sampled. The hearts and kidneys were then harvested and snap frozen by immersion in liquid nitrogen. Concentrations of VIP in plasma and tissue extracts were measured by radioimmunoassay. Plasma and renal concentrations of VIP did not change in the enalapril-treated rats. However, the myocardial concentration of VIP increased significantly in the rats receiving enalapril compared with control animals (p < 0.0005). We conclude that treatment with ACE inhibitors results in increased myocardial VIP concentrations and suggest that this may contribute to the improvement in cardiac function that occurs with these agents.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

A study of angiotensin II receptors after chronic inhibition of nitric oxide synthase in the spontaneously hypertensive rat.

1. Nitric oxide (NO) synthase inhibition, induces a sustained increase in blood pressure and amplifies the pressor response to infused angiotensin II (AngII). This study was designed to investigate the contribution of AngII receptors in the elevated blood pressure and enhanced pressor response to AngII in the spontaneously hypertensive rat (SHR) chronically treated with N(G)-nitro-L-arginine-methyl ester (L-NAME). 2. Two groups of 13 week old female SHR were housed four to a box. Group I rats received L-NAME for 7 days (2.5 mg/kg per day) in their drinking water. Group II rats received water only. Blood pressure was monitored daily by tail-cuff plethysmography. Plasma AngII was measured by radioimmunoassay. Aortic and uterine receptor binding was determined by saturation analysis using [125I]-Sar8, Ile1)AngII. Data was analysed using the computer program LIGAND. 3. Mean systolic blood pressure was significantly elevated in rats treated with L-NAME compared with the control group. Plasma AngII concentration was slightly decreased in rats treated L-NAME compared with control. Densities of both aortic and uterine AngII receptors increased significantly following NO synthase inhibition. Receptor affinity in the aorta decreased in the L-NAME group compared with control. However, uterine AngII receptor affinity was unchanged. 4. We conclude that the increased blood pressure and enhanced pressor responsiveness that occurs with chronic inhibition of NO synthesis may result partly from increased vascular AngII receptor expression.

Angiotensin II↗
PubMed1996

Angiotensin II: a humoral mediator for the gastric sodium monitor.

Natriuresis in direct response to a gastric sodium stimulus (upper-gut sodium monitor) has paradoxically only been demonstrated in humans and animals on a low-sodium diet preceding each study. It is possible that the low-sodium diet itself induces or suppresses systems that mediate or oppose the ensuing natriuresis. In this study, we sought to determine whether a system activated by this diet, the renin-angiotensin system, mediates the natriuretic response. Specifically, we sought to show whether changes in the circulating concentration of angiotensin II (ANG II) may mediate the renal response to stimulation of the gastric sodium monitor. Male New Zealand White rabbits were randomly assigned to low- (0.008%) or normal (2.2%) sodium diets. After 1 wk on the experimental diet, they received a sodium load intragastrically or intravenously, and plasma ANG II was measured at 0, 5, 10, 30, 60, and 120 min. Urine was collected for 4 h after the sodium load, and plasma sodium was measured at 0, 2, and 4 h. Urinary sodium excretion was greater in the 4 h after gastric than after intravenous sodium administration (P < 0.025) in the rabbits on the low-sodium diet. No significant difference was noted in the rabbits on the normal sodium. In rabbits on the low-sodium diet, there was an immediate and significant decline in plasma ANG II after sodium was administered both intragastrically (P < 0.025) and intravenously (P < 0.05). This decrease was greater after intragastric than intravenous sodium (P < 0.0025), and the difference was still evident at 120 min (P < 0.05). No significant difference in plasma ANG II was found in the normal diet group. We conclude, therefore, that a prolonged decrease in ANG II concentration may play a role in mediating the natriuretic response to the gastric sodium monitor.

Angiotensin II↗
PubMed1995

Effects of endopeptidase 24.11 inhibition on plasma and tissue concentrations of vasoactive intestinal peptide.

1. In this study, we sought to determine the effect of endopeptidase 24.11 inhibition on the rate of metabolism of vasoactive intestinal peptide. The effect of such inhibition on the concentration of vasoactive intestinal peptide in two tissues was also investigated. 2. Male Sprague-Dawley rats were given the endopeptidase 24.11 blocker UK77,568 (10 mg/kg) or vehicle as a single intravenous injection or as a daily injection for 4 days. Two hours after the final or single injection, the rats were anaesthetized and blood was sampled to determine plasma concentrations of vasoactive intestinal peptide and angiotensin II. The hearts and kidneys were harvested and snap-frozen in liquid nitrogen. The plasma and tissue concentrations of vasoactive intestinal peptide and the plasma concentration of angiotensin II were determined by radioimmunoassay. In a separate group of experiments, male Sprague-Dawley rats were anaesthetized and carotid and jugular catheters were inserted. One hour after intravenous administration of UK77,568 or vehicle, an infusion of vasoactive intestinal peptide (10 pmol min-1 kg-1) was commenced via the jugular catheter. Blood was sampled to determine the vasoactive intestinal peptide concentration 1 h after commencing the vasoactive intestinal peptide infusion to calculate the metabolic clearance rate. 3. Plasma vasoactive intestinal peptide increased after acute (P < 0.05) but not chronic administration of UK77,568, while the concentration of vasoactive intestinal peptide in the heart increased after chronic administration (P < 0.0005). The concentration of vasoactive intestinal peptide in the kidney was unchanged after both acute and chronic endopeptidase 24.11 blockade. Plasma angiotensin II decreased significantly in the chronic group (P<0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1995

Effects of sodium depletion on tissue concentrations of the natriuretic hormone vasoactive intestinal peptide.

1. Variations in dietary sodium intake have been shown to affect the plasma concentration, the metabolic clearance rate and secretion rate of vasoactive intestinal peptide (VIP). In this study we sought to determine the effect of sodium depletion on the concentration of VIP in plasma and in three tissues, namely heart, lung and kidney. 2. Male Sprague-Dawley rats were placed on low or normal sodium diets and drinking water ad libitum. A third group was placed on a low salt diet and in addition were given frusemide, 1mg/kg per day in the drinking water. After 7 days the rats were killed, a blood sample collected and tissues harvested. VIP concentrations were determined by radioimmunoassay on unextracted plasma and in tissue after extraction. 3. There were significant differences between the three groups in the concentration of VIP in the lung (P < 0.0005), kidney (P < 0.005) and plasma (P < 0.025) but not the heart. In the group that received frusemide and the low sodium diet, VIP in the lung was significantly lower than the low sodium (P < 0.005) and normal sodium (P < 0.0001) groups. Similar differences were noted in the kidney (frusemide vs low sodium, P < 0.001; frusemide vs normal, P < 0.01) and plasma (frusemide vs low sodium P < 0.001, frusemide vs normal P < 0.05). 4. We conclude that sodium depletion decreases the concentration of VIP in plasma and in its metabolizing tissues.

Animals↗
PubMed1995

Vasoactive intestinal peptide regulates angiotensin II catabolism in the rabbit.

Although vasoactive intestinal peptide (VIP) is natriuretic it stimulates renin and aldosterone secretion. Therefore, to effect a natriuresis, VIP may need to modulate the sodium conserving actions of the renin angiotensin system (RAS) by another means. One possibility is that it alters the rate of disappearance from the circulation of one or more components of the RAS. We sought to determine whether VIP regulates the rate of catabolism of angiotensin II (Ang II). Steady state metabolic clearance studies of Ang II were undertaken with and without simultaneous VIP infusion. These studies were performed in rabbits on low, normal and high sodium diets, as dietary sodium has been shown to affect the metabolism of both VIP and Ang II. The effects of VIP on plasma Ang II concentration and secretion were also studied. VIP decreased Ang II catabolism in rabbits on low (P < 0.05) and normal sodium diets (P < 0.05). Plasma levels of Ang II increased significantly in response to VIP in rabbits on these diets (low, P < 0.04; normal, P < 0.05). In contrast, in rabbits on a high sodium diet VIP increased the rate of catabolism of Ang II (P < 0.001). Thus we conclude that the effect of VIP on sodium excretion may be modulated by its effects on Ang II metabolism. The decrease in Ang II catabolism seen in rabbits on low and normal sodium diets may prevent or ameliorate any natriuresis while the more rapid degradation of Ang II which occurs in dietary sodium excess may enhance the natriuretic effect of VIP.

Angiotensin II↗