Urocortin 1 administration from onset of rapid left ventricular pacing represses progression to...

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Urocortin1administrationfromonsetofrapidleftventricularpacingrepressesprogressiontoovertheartfailure

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ImpactFactor:3.84·DOI:10.1152/ajpheart.00377.2007·Source:PubMed

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UROCORTIN 1 ADMINISTRATION

FROM ONSET OF RAPID LEFT VENRICULAR PACING

REPRESSES PROGRESSION TO OVERT HEART FAILURE.

Miriam T. Rademaker 1

Chris J. Charles 1

A. Mark Richards 1

1 Christchurch Cardioendocrine Research Group, Department of Medicine,

The Christchurch School of Medicine, Christchurch, NEW ZEALAND.

Address correspondence to: Assoc. Prof. M.T. Rademaker,

Department of Medicine,

The Christchurch School of Medicine,

P.O. Box 4345, Christchurch, NEW ZEALAND.

Phone: 64-3-3640544

Fax: 64-3-3640525

Email: [email protected]

First Author: Rademaker

Conflict of Interest: None

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Copyright Information

Articles in PresS. Am J Physiol Heart Circ Physiol (May 25, 2007). doi:10.1152/ajpheart.00377.2007

Copyright © 2007 by the American Physiological Society.

Urocortin 1 represses heart failure development

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ABSTRACT:

Urocortin 1 (Ucn1) may be involved in the pathophysiology of heart failure (HF), but the impact of Ucn1

administration on progression of the disease is unknown. The aim of this study was to investigate the effects

of Ucn1 in sheep from the onset of cardiac overload and during the subsequent development of HF.

Eight sheep underwent two four-day periods of HF-induction by rapid left ventricular pacing (225bpm) in

conjunction with continuous intravenous infusions of Ucn1 (0.1ug/kg/hr) and a vehicle control (0.9%

saline).

Compared to control, Ucn1 treatment attenuated the pacing-induced decline in cardiac output (Day 4:

2.43+0.46 vs 3.70+0.89L/min, p<0.01) and rises in left atrial pressure (24.9+1.0 vs 11.9+1.1mmHg,

p<0.001) and peripheral resistance (38.7+9.4 vs 25.2+6.1mmHg/L/min, p<0.001). Ucn1 wholly prevented

increases in plasma renin activity (4.02+1.17 vs 0.87+0.1nmol/L/hr, p<0.001), aldosterone (1313+324 vs

413+174pmol/L, p<0.001), endothelin-1 (3.8+0.5 vs 2.0+0.1pmol/L, p<0.001) and vasopressin (10.8+4.1 vs

1.8+0.2pmol/L, p<0.05) seen during pacing alone, and blunted the progressive rises in plasma epinephrine

(2132+697 vs 1250+264pmol/L, p<0.05), norepinephrine (3.61+0.73 vs 2.07+0.52nmol/L, p<0.05), and

atrial (p<0.05) and brain (p<0.01) natriuretic peptide levels. Ucn1 administration also maintained urine

sodium excretion (Day 4: 0.75+0.34 vs 1.59+0.50mmol/hr, p<0.05) and suppressed pacing-induced falls in

creatinine clearance (p<0.05). These findings indicate that Ucn1 treatment from the onset of cardiac

overload has the ability to repress the ensuing hemodynamic and renal deterioration and concomitant

adverse neurohumoral activation, thereby delaying the development of overt HF. These data strongly support

a use for Ucn1 as a therapeutic option early in the course of the disease.

KEY WORDS: Urocortin, heart failure, cardiac output, hormones, renal function

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INTRODUCTION:

Urocortin 1 (Ucn1), a 40 amino acid peptide belonging to the corticotropin-releasing factor (CRF) family

(43), is reported to participate in the regulation of the cardiovascular system. The peptide is located in high

concentrations in the heart (24) and in endothelial and smooth muscle cells of the systemic vasculature

(12,17), and its peripheral distribution closely matches that of the CRF receptor type 2 (CRFR2) - the G

protein-coupled receptor reported to mediate its cardiovascular bioactivity (22,44). Systemic

administration of Ucn1 induces sustained arterial (6,22,44) and venous (38) dilatation, increases in

coronary blood flow and conductance, and positive inotropic and chronotropic effects (1,27,32,33,42).

Ucn1 has also been shown to prevent cell death in cultured cardiac myocytes exposed to hypoxia (26), and

to protect coronary endothelial function and significantly reduce infarct size, arrhythmias and oxidative

stress in the rat heart following ischemia/reperfusion injury (4,14,20).

The nature of Ucn1's cardiovascular actions, together with evidence that both ventricular (24,18) and

circulating (23,32) concentrations of the peptide are significantly elevated in heart failure (HF), invites

speculation that Ucn1 might act as a protective counterbalance to preserve cardiac function and circulatory

homeostasis in this syndrome. Indeed, we have recently shown that Ucn1 administration produces

considerable hemodynamic, endocrine and renal benefits in an experimental model of severe congestive

HF (32,33). However, its actions in normal health are greatly attenuated - with reduced effect on

hemodynamics and negligible influence on vasoactive hormones and kidney function (32). Given these

disparate results, the impact of Ucn1 treatment in mild HF, or early in the course of the disease, is

uncertain. We therefore investigated the integrated effects of Ucn1 infusion in sheep from the onset of

cardiac overload and during the subsequent development of cardiac decompensation and overt HF induced

by rapid left ventricular (LV) pacing.

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METHODS

SURGICAL PREPARATION:

Eight Coopworth ewes (47-60Kg) were instrumented via a left lateral thoracotomy under general

anesthesia (induced by 17mg/kg thiopentone; maintained with halothane/nitrous oxide) (10). Two

polyvinyl chloride catheters were inserted in the left atrium for blood sampling and left atrial pressure

(LAP) determination; a Konigsberg pressure-tip transducer inserted in the aorta to record mean arterial

pressure (MAP); an electromagnetic flow probe placed around the ascending aorta to measure cardiac

output (CO); a Swan-Ganz catheter inserted in the pulmonary artery for infusions, and a 7 French His-

bundle electrode stitched subepicardially to the wall of the left ventricle for pacing. A bladder catheter was

inserted per urethra for urine collections. Animals recovered for 14 days before commencing the study

protocol. During the experiments the animals were held in metabolic cages, fed a standard laboratory diet

(500g sheep pellets and 250g chaff/day - containing 80 mmol sodium; 200 mmol potassium) and had free

access to water.

STUDY PROTOCOL:

Each sheep underwent two separate periods of continuous rapid LV pacing (225 bpm) for 4 days to allow

the development of congestive HF (10,35). Ten days without pacing between phases allowed recovery to

normal pre-pacing levels for all indices measured. On initiation of pacing, the animals received a constant

4-day intravenous infusion of either ovine Ucn1 (0.1ug/kg/hr) (American Peptide Company Inc, USA) or a

vehicle control (50ml 0.9% saline/day) in a crossover design.

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MAP, LAP, CO and calculated total peripheral resistance (CTPR=MAP/CO) were recorded at 15 minute

intervals in the hour preceding pacing/treatment on study day 0 (baseline), at 0.5, 1, 2, 4 and 6 hours

following commencement of pacing/treatment, and then daily on study days 1-4. Hemodynamic

measurements were determined by on-line computer assisted analysis using established methods (11).

Blood samples were drawn from the left atrium (immediately following hemodynamic measurements) into

EDTA tubes on ice, centrifuged at 4oC and stored at -80oC before assay for Ucn1 (32), cyclic adenosine

monophosphate (cAMP) (Commercial Kit; Biotrak, Amersham, Little Chalfont, UK), arginine vasopressin

(AVP) (36), cortisol (19), atrial and brain natriuretic peptide (ANP and BNP respectively) (5,28), plasma

renin activity (PRA) (9), aldosterone (21), endothelin-1 (29), catecholamines (15) and

adrenocorticotrophic hormone (ACTH). ACTH was measured by radioimmunoassay (RIA) as detailed

previously (8), except samples were extracted over C18 SepPak columns prior to RIA. Extracts were

eluted with 80% isopropanol / 0.1% TFA, and dried at 37oC before being resuspended in assay buffer. All

samples from individual animals were measured in the same assay to avoid inter-assay variability. Plasma

electrolytes and hematocrit were measured with every blood sample taken.

Urine volume and samples for the measurement of urine cAMP, sodium, potassium and creatinine

excretion were collected over the 2 hours prior to pacing/treatment on study day 0 (baseline), at 2, 4 and 6

hours following commencement of pacing/treatment, and then daily on study days 1-4. Water intake was

measured as per urine output. The study protocol was approved by the Christchurch School of Medicine

and Health Sciences' Animal Ethics Committee.

STATISTICS:

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Results are expressed as mean+SEM. Differences between control and Ucn1 baseline data (mean of

measurements made within the hour pre-pacing/treatment) were compared using paired t-tests. Effects of

pacing (development of HF) were assessed by analysis of temporal changes over the control phase using

one-way repeated measures analysis of variance (ANOVA). Differences between control and Ucn1

treatments were analysed by two-way ANOVA (treatment/time interactions quoted in text). Where

significant differences were identified by ANOVA, the level of significance at individual time points in

Figures 1-5 and Table 1 was determined by Fisher's protected least-significant difference tests.

The Ucn1 treatment arm of the study was also analysed separately by one-way ANOVA to assess temporal

changes (or rather lack thereof) in indices which appeared to alter little from baseline over the 4 days of

pacing. Significance was assumed at p<0.05.

RESULTS

Effects of Rapid Left Ventricular Pacing:

No significant baseline differences were noted between the control and Ucn1 study arms.

Four days of rapid LV pacing during the control phase of the study induced the hemodynamic

deterioration, ubiquitous hormonal activation and sodium-retaining hallmarks of congestive HF. We noted

marked, progressive reductions in CO (Control baseline vs Day 4: 6.96+1.76 vs 2.43+0.46 L/min,

p<0.001) and MAP (85.6+2.5 vs 73.2+3.6 mmHg, p<0.001), and increases in LAP (3.5+0.4 vs 24.9+1.0

mmHg, p<0.001) and CTPR (16.7+3.9 vs 38.7+9.4 mmHg/L/min, p<0.001) (Figure 1). These changes

were associated with significant rises in plasma Ucn1 (16.2+1.3 vs 19.0+0.7 pmol/L, p<0.05), cAMP

(24.2+2.0 vs 34.2+4.3 pmol/L, p<0.01), AVP (1.45+0.11 vs 10.84+4.08 pmol/L, p<0.05) (Figure 2), PRA

(0.42+0.06 vs 4.02+1.17 nmol/L/hr, p<0.001), aldosterone (434+104 vs 1313+324 pmol/L, p<0.001),

endothelin-1 (1.9+0.1 vs 3.8+0.5 pmol/L, p<0.001) (Figure 3), ANP (27+6 vs 177+22 pmol/L, p<0.001),

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BNP (4+1 vs 54+8 pmol/L, p<0.001), epinephrine (436+61 vs 2132+697 pmol/L, p<0.001),

norepinephrine (3.44+0.64 vs 3.611+0.73 pmol/L, p<0.001) (Figure 4) and creatinine levels (0.078+0.006

vs 0.094+0.008 mmol/L, p<0.001) (Table 1).

Rapid pacing also reduced creatinine clearance (103+8 vs 71+7 ml/min, p<0.001) (Table 1), and urine

sodium (1.69+0.27 vs 0.75+0.35 mmol/hr, p<0.05), potassium (9.2+1.5 vs 4.5+1.0 mmol/hr, p<0.01) and

creatinine excretion (0.492+0.024 vs 0.426+0.015 mmol/hr, p<0.01) (Figure 5), with a similar trend

observed for urine output (52+17 vs 38+38 ml/hr, p=0.089) (Figure 5) and water intake (144+42 vs

104+15 ml/hr, p=0.068) (Table 1).

Plasma ACTH levels rose transiently over the first hours of pacing (p<0.05) (Figure 2), whilst hematocrit,

and plasma sodium and potassium concentrations were not significantly altered over the 4-day pacing

period (Table 1).

Ucn1 Treatment:

Ucn1 infusion in conjunction with rapid pacing noticeably attenuated the decline in CO (Day 4: Control

2.43+0.46 vs Ucn1 3.70+0.89 L/min, p<0.01) and rises in LAP (24.9+1.0 vs 11.9+1.1 mmHg, p<0.001)

and CTPR (38.7+9.4 vs 25.2+6.1 mmHg/L/min, p<0.001) (Figure 1) seen with pacing alone during the

control phase. MAP (Figure 1) and hematocrit (Table 1) responses did not differ significantly between

treatments.

Infusion of Ucn1 raised circulating concentrations of the peptide (19+1 vs 2856+557 pmol/L, p<0.001),

and repressed pacing-induced elevations in plasma cAMP (34.2+4.3 vs 25.0+1.3 pmol/L, p<0.05) and

AVP (10.8+4.1 vs 1.8+0.2 pmol/L, p<0.05) (Figure 2). Acute increases in plasma ACTH and cortisol seen

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in the hours after commencement of Ucn1 treatment (both p<0.05) were not evident over Days 1-4 (Figure

2).

Ucn1 administration inhibited the rises in PRA (4.02+1.17 vs 0.87+0.09 nmol/L/hr, p<0.001), aldosterone

(1313+324 vs 413+174 pmol/L, p<0.001) and endothelin-1 (3.8+0.5 vs 2.0+0.1 pmol/L, p<0.001) noted

during pacing alone (Figure 3), and attenuated the increases in plasma ANP (177+22 vs 143+22 pmol/L,

p<0.05), BNP (54+8 vs 39+7 pmol/L, p<0.01), epinephrine (2132+697 vs 1250+264 pmol/L, p<0.05) and

norepinephrine (3.61+0.73 vs 2.07+0.52 nmol/L, p<0.05) (Figure 4).

Analysis of the Ucn1 phase alone (via one-way ANOVA) established that Ucn1 treatment prevented any

significant change in plasma cAMP, AVP, PRA and endothelin-1 from baseline levels over the 4 days of

pacing, whilst aldosterone concentrations actually tended to fall (Baseline 505+91 vs Day 2 243+40

pmol/L, p=0.0836).

In addition to inducing acute (2-6 hours) rises in urine volume (p<0.05), sodium (p<0.05) and creatinine

output (p<0.05), Ucn1 treatment maintained sodium excretion throughout the study period (Day 4:

0.75+0.34 vs 1.59+0.50 mmol/hr, p<0.05), and alleviated the declines urine creatinine (0.426+0.015 vs

0.448+0.028 mmol/hr, p<0.05) (Figure 5) and creatinine clearance (70.5+6.8 vs 84.7+6.3 ml/min, p<0.05)

(Table 1) observed over 4 days of pacing alone. A similar trend was evident for urine cAMP excretion

(p=0.089) (Figure 5). Plasma sodium and creatinine concentrations were decreased compared to control

(both p<0.05) (Table 1), whilst plasma and urine potassium (Table1 and Figure 5 respectively) and water

intake (Table 1) did not differ significantly.

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DISCUSSION:

The present study demonstrates that infusion of Ucn1 from the initiation of rapid LV pacing significantly

attenuates the hemodynamic deterioration (reductions in CO and rises in LAP and CTPR) and deleterious

hormonal activation (renin-aldosterone, endothelin-1, vasopressin, catecholamines) associated with the

development of congestive HF seen in untreated animals. Renal function was also protected, as assessed

by the maintenance of sodium excretion and blunted decline in creatinine clearance.

In this model of low output HF, the comparative preservation of CO observed with Ucn1 administration

may be due in part to the positive inotropic effects of the peptide, as reported previously in the isolated rat

heart (42), since arterial blood pressure (afterload) was matched in both treatment groups (and rises in LV

filling pressure were repressed). Additional actions of Ucn1 to dilate coronary arteries (42), and improve

cardiac bioenergetics (including the preservation of high-energy phosphate stores (39) which are depleted

in chronic tachycardia (7)) may also have contributed to the conservation of heart function. Whilst a lesser

fall in MAP might have been expected in Ucn1 treated animals given the smaller decline in CO, this was

presumably offset by the concomitant attenuated increase in systemic vascular resistance. This latter

response likely reflects the direct vasodilator action of Ucn1 (40) (reported to be mediated by both cAMP

and nitric oxide) (22), as well as the absent or blunted activation of a number of vasoconstrictor systems

(including endothelin-1, renin-angiotensin, AVP and sympathetic systems).

Infusion of Ucn1 on initiation of rapid LV pacing also substantially restricted the rise in LAP seen in

control animals, presumably as a result of the lesser reduction in CO, although lusitropic (3) and

venodilating (38) effects of the peptide may also have played a part. These results are consistent with the

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hemodynamic actions of Ucn1 demonstrated in severe HF (32,33) and indicate Ucn1 may be particularly

useful as an anti-failure therapy when administered early in the course of the disorder.

One of the most striking findings of the present study was the impact of Ucn1 administration on

neurohumoral activation during the serial deterioration of cardiovascular function. Although

demonstrating a significantly better hemodynamic profile than the control group after 4 days of rapid LV

pacing, Ucn1-treated animals still exhibited a 44% reduction in CO and 17% fall in MAP, together with a

3.8- and 1.5-fold rise in LAP and CTPR, respectively (Controls: 65% and 15% falls in CO and MAP, and

7.2- and 2.3-fold increases in LAP and CTPR, respectively). Despite this hemodynamic insult, Ucn1

administration wholly prevented any significant rise in circulating PRA (despite drops in blood pressure,

and presumably renal perfusion pressure, equal to that in untreated animals), and actually tended to reduce

plasma aldosterone levels relative to pre-pacing baseline. This contrasted with 10- and 3-fold rises in the

respective factors in the untreated animals. Whether the suppression of PRA was due to increased delivery

of sodium to the macula densa (evidenced by significant rises in sodium excretion over days 1-3),

elevations in plasma concentrations of the natriuretic peptides, a direct inhibitory effect of Ucn1 on renin

secretion, or some other PRA-suppressive mechanism is unknown. The trend for aldosterone levels to

decline over this same period, where plasma ACTH and potassium were unchanged, might suggest a

possible direct inhibitory effect of Ucn1 on the hormone's secretion, especially given the strong

immunoreactivity of Ucn1 demonstrated in the medulla of the adrenal gland (13). Alternatively, possible

Ucn1-induced reductions in serum angiotensin-converting enzyme (ACE) activity (45) might explain the

aldosterone fall in the present study, via decreased angiotensin II (a prime secretagogue for aldosterone in

HF).

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Increments in plasma endothelin-1 levels were also fully repressed by Ucn1 administration during rapid

LV pacing, in contrast to the doubling of levels observed in the control group. Although a direct effect of

Ucn1 on endothelin secretion is yet to be investigated, Ucn1 has been reported to potently oppose the

vasoconstricting actions of the peptide (38,44), and blockade of the Ucn system in experimental HF results

in further elevations in circulating endothelin-1 (34). Whilst it is conceivable that the prominent rises in

ANP and BNP may have played a role in repressing endothelin production (16), significantly greater

increments of the natriuretic peptides in the control group were not associated with endothelin

suppression. Furthermore, reductions in sheer stress (as judged by falls in MAP), a stimulatory factor for

endothelin-1 secretion (16), were comparable in both treatment groups.

The mechanism/s mediating the complete inhibition of increased AVP secretion with Ucn1 infusion

(compared to a 7-fold rise in untreated sheep), which occurred in the face of significant declines in CO and

pressure at sinoaortic volume receptors, cannot be determined from the present study.

Whilst not as striking as the inhibition of the other vasoconstrictor factors (above), activation of the

sympathetic nervous system was still significantly blunted with Ucn1 treatment over the 4 day pacing

period. This likely reflects the comparative preservation of heart function demonstrated in this group (2).

The actions of Ucn1 to wholly or significantly suppress these deleterious vasoconstrictor systems in the

face of persisting substantive deterioration of cardiac and hemodynamic status is truly remarkable and

strongly encourages further investigation of Ucn1 as a potential treatment in the early phase of HF,

especially given that the maladaptive activation of these systems plays an important role in the down-ward

spiral of this disease.

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Elevations in plasma concentrations of the natriuretic peptides were also attenuated with Ucn1

administration. Yet it should be noted that whereas the rise in LAP (a major stimulus for ANP secretion)

in the Ucn1-treated sheep was half that seen in untreated animals, the increase in plasma ANP was 81% of

that observed in the control group. This finding is in keeping with reports demonstrating Ucn1 enhances

the production of the natriuretic peptides from cardiomyocytes (24), which is likely to be beneficial in a

disease characterised by vasoconstriction and volume retention. Despite major elevations in circulating

levels of Ucn1 with infusion of the peptide, plasma concentrations of cAMP - a proposed intracellular

second messenger of Ucn1 (40), were largely unaltered, and remained significantly lower than

concentrations seen in the untreated animals (which exhibited only a moderate increase in endogenous

Ucn1). However, cAMP is a second messenger utilized by many systems activated in HF, and the failure

of levels to rise in the Ucn1-treated animals likely reflects the less severe disease status achieved in this

group (25). Nevertheless, cAMP was either raised sufficiently at the level of cell signaling to induce the

significant effects observed with Ucn1 administration, or, alternatively, other pathways may be involved

(22,37,42).

Ucn1 administration prevented the avid sodium retention associated with the development of HF, and

actually induced a natriuresis over the first 3 days of treatment, with a corresponding relative decrease in

plasma sodium levels. Ucn1 further alleviated the marked decline in glomerular filtration rate (GFR) (as

judged by falls in creatinine clearance) seen in control animals. Whilst it is likely that the significant

elevation in circulating natriuretic peptides contributed to this effect (where there were no matching rises

in anti-natriuretic factors such as angiotensin II, aldosterone, AVP, and endothelin-1), it is also possible

Ucn1 has direct tubular actions given reports of the peptide's expression within the kidney (41) and a trend

for urine cAMP excretion to increase in the present study. Although blood pressure, and therefore

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presumably renal perfusion pressure, was reduced over this period, the effect of Ucn1 to also cause

vasodilation of renal blood vessels (37), may have acted to conserve hemodynamic function within the

kidney. Whatever the mechanisms, we have shown the relative preservation of renal function by Ucn1

during the development of a disease that is further exacerbated by declining kidney performance.

We have previously investigated the acute effects of the three known forms of Ucn (Ucn1, Ucn2, Ucn3) in

overt HF (30,31,32) and have shown that they elicit a very similar range and magnitude of beneficial

hemodynamic, neurohormonal and renal responses, suggesting it is likely that any one of the Ucn isoforms

will act equally successfully in the setting of early cardiac dysfunction or decompensation.

Although rapid LV pacing induces the hemodynamic, hormonal and renal characteristics of (low CO)

congestive HF, it should be noted that this models only one form of HF and may not reflect some others. A

further limitation of this study is the lack of data concerning the direct effect of Ucn1 on ventricular

dimensions and function (measured by either echocardiography or sonomicrometry). Future investigations

into Ucn1's impact on these parameters, especially over more extended treatment periods, are awaited with

great interest.

In summary, this study demonstrates that sustained Ucn1 treatment following the onset of rapid left

ventricular pacing has the ability to repress the ensuing progressive cardiorenal deterioration, largely

prevent the activation of adverse vasoconstrictor/antinatriuretic hormone systems and augment plasma

natriuretic peptide levels, thereby delaying the progression to overt HF. Given the beneficial responses to

Ucn1 demonstrated in this model of HF, assessment of the peptide (or its analogues) as a therapeutic

option early in the course of episodes of acute clinical HF (such as may occur during acute exacerbation of

stable compensated HF, or HF induced by myocardial infarction) seems appropriate.

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ACKNOWLEDGMENTS:

This study was supported by grants from the Health Research Council and the National Heart Foundation

of New Zealand. We are grateful to the staff of the Endocrine Laboratory for hormone assays, and the

Christchurch School of Medicine Animal Laboratory for animal care.

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LEGEND FOR FIGURE 1.

Mean+SEM hemodynamic responses to initiation of rapid left ventricular (LV) pacing in conjunction with

infusions of a vehicle control (Ο) and Ucn (0.1ug/kg/hr) (�) in 8 sheep. Significant differences are shown

by: *p<0.05, **p<0.01, + p<0.001.


Mean+SEM plasma urocortin 1, cyclic adenosine monophosphate (AMP), arginine vasopressin,

adrenocorticotrophic hormone (ACTH) and cortisol responses to initiation of rapid left ventricular (LV)

pacing in conjunction with infusions of a vehicle control (Ο) and Ucn (0.1ug/kg/hr) (�) in 8 sheep.

Significant differences are shown by: *p<0.05, **p<0.01, + p<0.001.


Mean+SEM plasma renin, aldosterone and endothelin-1 responses to initiation of rapid left ventricular

(LV) pacing in conjunction with infusions of a vehicle control (Ο) and Ucn (0.1ug/kg/hr) (�) in 8 sheep.

Significant differences are shown by: *p<0.05, **p<0.01, + p<0.001.


Mean+SEM and atrial and brain natriuretic peptide, epinephrine and norepinephrine responses to initiation

of rapid left ventricular (LV) pacing in conjunction with infusions of a vehicle control (Ο) and Ucn

(0.1ug/kg/hr) (�) in 8 sheep. Significant differences are shown by: *p<0.05, **p<0.01, + p<0.001.


Mean+SEM urine volume, and sodium, potassium, creatinine and cyclic adenosine monophosphate

(cAMP) excretory responses to initiation of rapid left ventricular (LV) pacing in conjunction with

infusions of a vehicle control (Ο) and Ucn (0.1ug/kg/hr) (�) in 8 sheep. Significant differences are shown

by: *p<0.05, **p<0.01, + p<0.001.

Page 22 of 28



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23

Table 1. Effects of Ucn treatment on the development of pacing-induced heart failure.

Baseline ----------------------- Pacing + Treatment ---------------------------

Day 0 Day 1 Day 2 Day 3 Day 4

Hematocrit (%)

Control 26.6+0.7 28.4+0.7 28.3+1.1 28.6+1.3 28.0+1.2

Ucn 26.4+0.8 29.1+0.9 28.9+1.1 29.9+1.1 29.6+1.2

Plasma sodium (mmol/L)

Control 146.4+0.4 147.6+0.6 146.6+0.6 146.0+0.8 146.1+0.9

Ucn 146.5+0.9 146.1+0.4 * 145.6+0.5 146.0+ 0.9 145.1+0.8

Plasma creatinine (mmol/L)

Control .078+.006 .087+.007 .090+.007 .096+.007 .094+.008

Ucn .078+.007 .083+.006 .080+.005 ** .080+.005 + .083+.007 **

Plasma potassium (mmol/L)

Control 4.10+0.07 4.08+0.11 4.09+0.12 4.10+0.13 4.19+0.15

Ucn 4.11+0.12 3.95+0.6 4.14+0.05 4.21+0.07 4.34+0.06

Creatinine clearance (ml/min)

Control 103+8 84+8 82+8 74+8 71+7

Ucn 100+9 92+5 * 94+7 * 92+8 + 85+6 **

Water intake (ml/hr)

Control 144+42 95+20 96+7 97+17 104+15

Ucn 134+36 78+20 69+15 91+13 92+17

FOOTNOTES FOR TABLE 1.

Mean+SEM measurements before (Day 0) and following initiation of rapid left ventricular pacing in

conjunction with continuous infusions of a vehicle control and Ucn (0.1ug/kg/hr) (Days 1-4) in 8 sheep.

Significant differences between control and Ucn are shown by: *p<0.05, **p<0.01, + p<0.001.

Page 23 of 28


5.0

4 .0

6 .0

3 .0

7 .0

0 62 4 41 32

Time (hours)

8 6

8 2

7 8

7 0

Cardiac

output

(L/min)

Left atrial

pressure

(mmHg)

2 5

2 0

1 5

1 0

Mean arterial

pressure

(mmHg)7 4

5

Time (days)

Calculated

total

peripheral

resistance

(mmHg/L/min)

4 0

3 5

3 0

2 0

=

** ***

Figure 1

2 5

1 5

0

**

***

*

==

=

===

=

Vehicle ( ) / Urocortin infusion (0.1 ug/kg/hr) ( )

Induction of heart failure by rapid LV pacing (225 bpm)

Page 24 of 28


1000

0

3 5

0 62 4 41 32

Time (hours)

3 0

2 5

2 0

8

4

0

5 0

2 5

1 2

2 0

Time (days)

1 0

5

130

9 0

=

***

Figure 2

110

7 0

1 5

2000

3000

Plasma

urocortin

(pmol/L)

Plasma

cyclic

AMP

(nmol/L)

Plasma

arginine

vasopressin

(pmol/L)

Plasma

ACTH

(pmol/L)

Plasma

cortisol

(nmol/L)

= == =

=

==

*

*

** **

** ** **

**



Page 25 of 28


0 62 4 41 32

Time (hours) Time (days)

=

**

*

Figure 3

3.0

4 .0

2 .0

1 .0

0

1200

Plasma

renin

activity

(nmol/L/hr)

Plasma

endothelin-1

(pmol/L)

1000

600

400

3.5

3 .0

1 .5

2 .5

2 .0

Plasma

aldosterone

(pmol/L)

200

800

4.0

=

=

=

=

==

*



Page 26 of 28


0 62 4 41 32

Time (hours)


Time (days)

=

**

*

Figure 4

140

180

100

6 0

2 0

5 0

4 0

2 0

1 0

2000

Plasma

atrial

natriuretic

peptide

(pmol/L)

1500

0

1000

500

Plasma

brain

natriuretic

peptide

(pmol/L)

3 0

1 0

0

2 0

0

3 0

Plasma

norepinephrine

(nmol/L)

Plasma

epinephrine

(pmol/L)

220

=

=

=

**

**

****

*

*


Page 27 of 28


0

100

5 0

1 2

2 5

0 62 4 41 32

Time (hours)

8

Vehicle ( ) / Urocortin infusion (0.1ug/kg/hr)( )

2

Urine

output

(ml/hr)

0.42

Time (days)

Urine

sodium

excretion

(mmol/hr)

Urine

creatinine

excretion

(mmol/hr)

0.50

0.48

0.46

0.44

Urine

cyclic AMP

excretion

(nmol/hr)

200

100

***

=

Figure 5

7 5

Urine

potassium

excretion

(mmol/hr)

0

1

2

3

4

5

1 0

6

4

150

250

300

*** *

*

**

**

***

*

Heart failure induction by rapid LV pacing (225bpm)

Page 28 of 28


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