Reduction of the accumulation of advanced glycation end products by ACE inhibition in experimental diabetic nephropathy

The effect of ACE inhibition on the formation of advanced glycation end products (AGEs) and oxidative stress was explored. Streptozocin-induced diabetic animals were randomized to no treatment, the ACE inhibitor ramipril (3 mg/l), or the AGE formation inhibitor aminoguanidine (1 g/l) and followed for 12 weeks. Control groups were followed concurrently. Renal AGE accumulation, as determined by immunohistochemistry and both serum and renal fluorescence, were increased in diabetic animals. This was attenuated by both ramipril and aminoguanidine to a similar degree. Nitrotyrosine, a marker of protein oxidation, also followed a similar pattern. The receptor for AGEs, gene expression of the membrane-bound NADPH oxidase subunit gp91phox, and nuclear transcription factor-kappaB were all increased by diabetes but remained unaffected by either treatment regimen. Two other AGE receptors, AGE R2 and AGE R3, remained unchanged for the duration of the study. The present study has identified a relationship between the renin-angiotensin system and the accumulation of AGEs in experimental diabetic nephropathy that may be linked through oxidative stress

Up-regulation of components of the renin-angiotensin system in the bile duct-ligated rat liver

BACKGROUND & AIMS

Angiotensin II (ANG II) has profibrotic actions in the heart and kidney, whereas blockade of the renin angiotensin system (RAS) attenuates injury. This study examines whether the RAS is present in the liver and examines its regulation in the bile duct-ligation model of hepatic fibrogenesis.

METHODS

Sham-operated and bile duct-ligated (BDL) Sprague-Dawley rats were studied. Gene and protein expression of hepatic renin, angiotensinogen, angiotensin-converting enzyme (ACE), and the angiotensin receptors AT1 and AT2 were assessed using real-time reverse-transcription polymerase chain reaction, in vitro autoradiography, and immunohistochemistry.

RESULTS

Angiotensinogen and renin messenger RNA were detected in sham liver but were not increased following BDL. Angiotensinogen protein was widely distributed in hepatocytes in both normal and injured livers, but in BDL livers, it was also expressed within areas of active fibrogenesis. Both ACE and AT1 receptor genes were up-regulated following BDL. The low level of ACE activity in sham animals was significantly increased in areas of active fibrogenesis in BDL livers. The AT1 receptor was present in both normal and diseased liver parenchyma, with increased AT1 receptor binding seen in fibrotic areas in the diseased liver. The AT2 receptor gene was not detected in normal or diseased liver.

CONCLUSIONS

Key elements of the RAS are present in normal liver tissue, and there is major up-regulation of the system in the bile duct-ligated liver. These findings are in keeping with recent experimental studies that have demonstrated antifibrotic effects of RAS blockade in the bile duct-ligated liver.

Combined inhibition of neutral endopeptidase with angiotensin converting enzyme or endothelin converting enzyme in experimental diabetes

OBJECTIVE

The effects of combined inhibition of neutral endopeptidase (NEP) with either angiotensin-converting enzyme (ACE), or endothelin-converting enzyme (ECE) on blood pressure, urinary albumin excretion and heart weight were explored in experimental diabetes.

DESIGN

Streptozotocin-induced diabetic Sprague-Dawley rats were treated with vehicle, the NEP/ACE inhibitor S 21402, the NEP/ECE inhibitor CGS 26303, the NEP inhibitor SCH 42495, the ACE inhibitor captopril or the endothelin receptor antagonist bosentan for 4 weeks.

METHODS

Blood pressure was measured by tail-cuff method and radiotelemetry. Albuminuria, plasma renin activity and plasma atrial natriuretic peptide (ANP) were determined by radioimmunoassay. NEP binding was assessed by in vitro quantitative autoradiography. Metabolic and biochemistry parameters including food intake, 24-h urine volume, plasma glucose, glycated hemoglobin, glomerular filtration rate (GFR) and urinary sodium excretion were also determined.

RESULTS

Mean blood pressure over the 4-week study period after commencement of treatment was reduced to a similar extent by a range of treatments including the ACE inhibitor, NEP/ACE inhibitor, endothelin receptor antagonist, NEP/ECE inhibitor, but not the NEP inhibitor, compared with vehicle-treated diabetic rats. Heart to body weight ratio in diabetic rats was only reduced by the NEP/ACE and the NEP/ECE inhibitor. Increased albuminuria in diabetic rats (1.1 times/divided by 1.2 mg/day) was reduced by the NEP/ACE (0.6 times/divided by 1.2 mg/day) and the NEP/ECE inhibitors (0.4 times/divided by 1.2 mg/day). Renal NEP was reduced by the NEP/ACE inhibitor (35 +/- 4%) or NEP/ECE inhibitor (38 +/- 4%) as well as by the pure NEP inhibitor (27 +/- 4%) compared with the untreated diabetic group. Other abnormal metabolic and biochemical parameters in diabetic rats were not influenced by any drug treatment.

CONCLUSIONS

Combined inhibition of NEP/ACE or NEP/ECE confers beneficial effects on blood pressure, albuminuria and heart to body weight ratio in experimental diabetes.

Neurohormonal antagonism in heart failure; beneficial effects of vasopressin V(1a) and V(2) receptor blockade and ACE inhibition

OBJECTIVE

To assess the long-term efficacy of vasopressin (AVP) V(1a) and V(2) receptor blockade with conivaptan, alone and in combination with angiotensin converting enzyme (ACE) inhibition on blood pressure, metabolic and neurohormonal parameters, and cardiovascular structure in a rat model of congestive heart failure (CHF).

METHODS

CHF was induced by left coronary artery ligation. CHF rats received conivaptan (1 mg/kg/day), ACE inhibition (captopril, 50 mg/kg/day), conivaptan and captopril (Combination) or vehicle for 4 weeks. Blood pressure was measured weekly, metabolic caging studies performed at 25 days, and rats killed and blood and tissue collected after 4 weeks treatment.

RESULTS

Combination treatment lowered blood pressure (P<0.01), and conivaptan and Combination caused an aquaresis (P<0.01). Combination decreased plasma natriuretic peptide (P<0.05), reduced left and right ventricular mass (P<0.01) and lung mass (P<0.05).

CONCLUSIONS

In CHF, blockade of vasopressin V(1a) and V(2) receptors was associated with increased water excretion, and the combination of conivaptan with ACE inhibition was the only treatment to reduce blood pressure, natriuretic peptide and pulmonary congestion. These results suggest conivaptan may be a useful addition to ACE inhibitors in the management of vasoconstriction and fluid retention that characterizes CHF.

Evidence for cardioprotective, renoprotective, and vasculoprotective effects of vasopeptidase inhibitors in disease

In both the natriuretic peptide and renin-angiotensin systems, peptidases play an important role in the inactivation or activation of the system. Angiotensin-converting enzyme is responsible for the conversion of angiotensin I to angiotensin II, while neutral endopeptidase is one of the pathways involved in the degradation of the natriuretic peptides. The vasopeptidase inhibitors, which simultaneously inhibit neutral endopeptidase and angiotensin-converting enzyme, appear to offer distinct therapeutic advantages in treating hypertension, heart failure, and endothelial dysfunction.

Vasopeptidase inhibition attenuates the progression of renal injury in subtotal nephrectomized rats

BACKGROUND

Vasopeptidase inhibitors are a new class of cardiovascular compounds that inhibit both angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP). The aim of the present study was to explore the effects of omapatrilat, a vasopeptidase inhibitor, on renal function and pathology in subtotally nephrectomized (STNx) rats.

METHODS

STNx rats were randomized to four groups and treated for 12 weeks: no treatment (N = 14); omapatrilat at a low dose of 10 mg/kg (L, N = 12) and at a high dose of 40 mg/kg (H, N = 10); or an ACE inhibitor, fosinopril, at a dose of 10 mg/kg (N = 12). Sham-operated rats were used as control animals (N = 12).

RESULTS

Elevated blood pressure in STNx rats (174 +/- 9 mm Hg) was reduced by omapatrilat in a dose-dependent manner (L, 121 +/- 3 mm Hg; H, 110 +/- 3 mm Hg) and by fosinopril (149 +/- 5 mm Hg). Proteinuria in STNx rats (246 +/- 73 mg/day) was reduced by treatment with fosinopril (88 +/- 21 mg/day) and was normalized by treatment with omapatrilat (L, 30 +/- 4 mg/day; H, 20 +/- 2 mg/day vs. control 25 +/- 1 mg/day). Decreased glomerular filtration rates, elevated plasma urea and creatinine and glomerulosclerosis, and tubulointerstitial fibrosis were ameliorated by omapatrilat and fosinopril to a similar degree. Compared with fosinopril, omapatrilat treatment was associated with increased plasma renin activity and decreased renal ACE and NEP binding in a dose-dependent manner.

CONCLUSION

These findings suggest that vasopeptidase inhibition may provide a useful strategy for the treatment of progressive renal disease.

In-vitro and in-vivo inhibition of rat neutral endopeptidase and angiotensin converting enzyme with the vasopeptidase inhibitor gemopatrilat

OBJECTIVES

Vasopeptidase inhibitors are single molecules that simultaneously inhibit neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE). The aim of this study was to characterize in-vitro and in-vivo inhibition of NEP and ACE in the rat with the vasopeptidase inhibitor gemopatrilat.

DESIGN AND METHODS

In-vitro NEP and ACE inhibition was studied by radioinhibitory binding assay using rat renal membranes and the specific NEP inhibitor radioligand 125I-RB104 and the specific ACE inhibitor radioligand 125I-MK351A, respectively (n = 3 per curve). In-vivo NEP and ACE inhibition was studied using in-vitro autoradiography in rats that received oral gemopatrilat (1, 3, 10 mg/kg; n = 4 per dose) and were killed 1 h later, or received oral gemopatrilat (3, 10 mg/kg) and were killed at time points 1, 2, 4, 8, 18, 24 and 48 h (n = 4 per time point).

RESULTS

Gemopatrilat caused a concentration-dependent displacement of specific radioligands from renal membrane NEP (IC50 305 +/- 5.4 nmol/I) and ACE (IC50 3.6 +/- 0.02 nmol/). In the dose-response study gemopatrilat (1, 3 and 10 mg/kg) caused significant inhibition of plasma ACE (P< 0.01), and renal ACE and NEP (3, 10 mg/kg, P < 0.01). In the time course experiment, gemopatrilat (10 mg/kg) increased plasma renin activity for 8 h (P< 0.01) and inhibited plasma ACE (P< 0.05), renal NEP (P< 0.01) and renal ACE (P< 0.05) for 48 h.

CONCLUSIONS

Gemopatrilat is a potent in-vitro vasopeptidase inhibitor that also causes prolonged inhibition of circulating and renal ACE and renal NEP after a single oral dose. The data suggest that gemopatrilat may be a useful addition to existing vasopeptidase inhibitors in the treatment of cardiovascular disease.

Thirst in elderly subjects

The hormonal changes associated with ageing, the occurrence of other medical condition and the use of medications increases the likelihood of conditions such as hyper- and hypo-natremia. Awareness of the homeostatic changes with age and the relations with disease and drugs will lead better management of fluid disorders in the elderly patient and hopefully a reduction in morbidity and mortality.

Beneficial renal and cardiac effects of vasopeptidase inhibition with S21402 in heart failure

S21402 is a vasopeptidase inhibitor that simultaneously inhibits neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE). This study determined whether chronic treatment with S21402 produced different effects on sodium and water excretion, hormonal parameters, and cardiovascular structure compared with selective inhibition of ACE and NEP in a rat model of myocardial infarction-induced congestive heart failure (CHF). CHF rats received the vasopeptidase inhibitor (S21402, 100 mg. kg(-1). d(-1)), an ACE inhibitor (captopril, 50 mg. kg(-1). d(-1)), a NEP inhibitor (SCH42495, 60 mg. kg(-1). d(-1)), or vehicle for 4 weeks. S21402 alone caused a diuresis and natriuresis (P<0.01) in CHF. After 4 weeks, blood pressure was lowered by captopril but not other treatments (P<0.01). Both S21402 and captopril increased plasma renin activity (P<0.01), all treatment lowered plasma aldosterone (P<0.05) and plasma natriuretic peptide levels were unchanged. In the kidney, S21402 inhibited NEP and ACE (P<0.01), SCH42495 inhibited NEP (P<0.01), and captopril inhibited ACE (P<0.01). Heart mass was reduced by all active treatments; captopril reduced left ventricular mass (P<0.01), SCH42495 reduced right ventricular mass (P<0.01), and S21402 decreased left (P<0.05) and right ventricular mass (P<0.01), atrial mass (P<0.05), and lung mass (P<0.01). In CHF, vasopeptidase inhibition with S21402 produces effects that differ from those of selective NEP or ACE inhibition. S21402 improved sodium and water excretion, reduced pulmonary congestion, and attenuated both right and left ventricular remodeling. These effects, which occurred in the absence of any hypotensive action, suggest that S21402 may offer several advantages over ACE inhibition alone in the treatment of heart failure.

Vasopressin V1a receptor antagonism does not reverse adrenocorticotrophin-induced hypertension in the rat

1. The role of arginine vasopressin (AVP) was examined in adrenocorticotrophin (ACTH)-induced hypertension in Sprague-Dawley rats using the non-peptide AVP V1a receptor antagonist OPC 21268. 2. In an acute study, six rats were pretreated with ACTH for 11 days and direct arterial blood pressure (4 h), plasma osmolality and electrolyte concentrations were measured after OPC 21268 gavage. In a chronic study, 40 rats were randomly divided into four groups: (i) sham injection + sham gavage; (ii) ACTH + sham gavage; (iii) sham injection + OPC 21268; or (iv) ACTH + OPC-21268 for 16 days. Systolic blood pressure (SBP), water intake, urine volume (UV), urine osmolality and electrolytes, food intake, bodyweight and plasma osmolality and electrolyte concentrations were measured. 3. In the acute study, direct mean arterial blood pressure did not change with OPC 21268 (122+/-2 and 120+/-3 mmHg at 0 and 240 min, respectively). 4. In the chronic study, OPC 21268 did not affect ACTH-induced rises in blood pressure (from 125+/-2 (control) to 145+/-5 mmHg (group 4) compared with 122+/-3 (control) to 149+/-5 mmHg (group2)). Water intake and UV increased (from 29+/-2 to 83+/-6 mL/day; and from 5+/-1 to 36+/-5 mL/day, respectively) and the change in bodyweight decreased from 0+/-2 to -107+/-7 g. 5. These results suggest that AVP (at the V1a receptor) does not play a significant role in the maintenance of ACTH-induced hypertension.

Antihypertensive and antihypertrophic effects of omapatrilat in SHR

Vasopeptidase inhibitors, such as omapatrilat are single molecules that simultaneously inhibit neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE). In normotensive rats, a single dose of oral omapatrilat (10 mg/kg) and 1 mg/kg inhibited plasma ACE (P < .01) for 24 h and increased plasma renin activity for 8 h (P < .01). In vitro autoradiography using the specific NEP inhibitor radioligand 125I-RB104 and the specific ACE inhibitor radioligand 125I-MK351A showed omapatrilat (10 mg/kg) caused rapid and potent inhibition of renal NEP and ACE, respectively, for 24 h (P < .01). In spontaneously hypertensive rats, 10 days of oral omapatrilat (40 mg/kg/day) reduced blood pressure (vehicle 237 +/- 4 mm Hg; omapatrilat, 10 mg/kg, 212 +/- 4 mm Hg; omapatrilat 40 mg/kg, 197 +/- 4 mm Hg, P < .01) in a dose-dependent manner (10 v 40 mg/kg, P < .01). Left ventricular hypertrophy was significantly reduced by high-dose omapatrilat (vehicle 2.76 +/- 0.03 mg/g body weight; omapatrilat, 10 mg/kg, 2.71 +/- 0.02 mg/g; omapatrilat 40 mg/kg, 2.55 +/- 0.02 mg/g, P < .01) and omapatrilat also increased kidney weight compared to vehicle (both doses, P < .01). Omapatrilat caused significant inhibition of plasma ACE and increased plasma renin activity (both doses, P < .01), and in vitro autoradiographic studies indicated sustained inhibition of renal ACE and NEP (both doses, P < .01). Omapatrilat is a potent vasopeptidase inhibitor, and its antihypertensive effects are associated with inhibition of NEP and ACE at the tissue level and beneficial effects on cardiovascular structure. Relating the degree of tissue inhibition to physiologic responses may allow further definition of the role of local renin angiotensin and natriuretic peptide systems in the beneficial effects of vasopeptidase inhibitors.

Effects of neutral endopeptidase inhibition in the rat remnant kidney model

The orally active neutral metalloendopeptidase (NEP) inhibitor SCH34826 was given by oral gavage in a dose of 90 mg/kg twice daily for 3 days to rats with subtotal nephrectomy (n = 7) and effects were compared to a placebo group receiving phosphate buffer (n = 5). Inhibition of neutral endopeptidase in the remnant kidney was measured by in vitro autoradiography using the specific radioligand [125I]-SCH 47896. Treatment with the NEP inhibitor SCH34826 caused a 60% reduction in the neutral endopeptidase radioligand-binding site density in the kidneys of the SCH34826-treated animals compared to the placebo group (81.6+/-3.7 versus 214.5+/-4.2 dpm/mm2, p<0.01). This was associated with a marked increase in urinary atrial natriuretic peptide (ANP) from 3,930+/-295 to 9,094+/-1,089 pg/24 h in the SCH34826-treated group (p<0.01). Concomitantly there was a transient increase in natriuresis in the SCH34826-treated group [baseline 2.03+/-0.55 to 3.77+/-0.58 mmol/24 h on treatment day 1 (p = 0.02) and 2.58+/-0.19 mmol/24 h on treatment day 3 (p = 0.09)] which was not observed in the placebo group. Urinary protein excretion, glomerular filtration rate (determined by 99mTc-DTPA clearance), systemic blood pressure, plasma ANP concentration and urinary cyclic GMP excretion were not changed by SCH34826 treatment. These results suggest that oral administration of the NEP inhibitor SCH34826 inhibits renal neutral endopeptidase, increases urinary ANP and modulates natriuresis without alteration of systemic blood pressure, plasma ANP and renin level, glomerular filtration or protein excretion.

Reversal of cardiac hypertrophy and fibrosis by S21402, a dual inhibitor of neutral endopeptidase and angiotensin converting enzyme in SHRs

OBJECTIVE

The major advantage of dual inhibitors of neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE) is their ability to lower blood pressure irrespective of renin or volume status. The aim of this study was to determine whether dual NEP/ACE inhibition produces different effects on cardiovascular structure and fibrosis, hormonal parameters and inhibition of tissue enzymes compared with selective inhibition of ACE and NEP in the spontaneously hypertensive rat (SHR).

METHODS

Male SHRs received the dual NEP/ACE inhibitor (S21402, 100 mg/kg per day), the ACE inhibitor (captopril, 50 mg/kg per day), the NEP inhibitor (SCH42495, 60 mg/kg per day) or vehicle for 2 weeks.

RESULTS

S21402 produced equivalent blood pressure lowering effects to captopril (vehicle, 220 +/- 1 mmHg; S21402, 189 +/- 2 mmHg; captopril, 187 +/- 3 mmHg), but was a more effective antihypertensive agent than SCH42495 (214 +/- 2 mmHg, P< 0.01). All treatments reduced left ventricular mass (P< 0.05) and cardiac fibrosis (P< 0.01). S21402 inhibited renal NEP and ACE (P< 0.01), SCH42495 inhibited renal NEP (P < 0.01), and captopril inhibited renal ACE (P< 0.01). Captopril and S21402 increased plasma renin activity (P< 0.05), but the rise with S21402 was attenuated compared with that caused by captopril (P< 0.01). All treatments reduced plasma aldosterone levels (P< 0.01), and NEP inhibition with SCH42495 and S21402 increased plasma atrial natriuretic peptide (ANP; P< 0.05).

CONCLUSIONS

These results indicate that selective NEP inhibition has major benefits in the regression of cardiac hypertrophy and reduction of fibrosis but has limited antihypertensive effects. The dual NEP/ACE inhibitor S21402 offered no advantage over the selective ACE inhibitor in terms of blood pressure reduction, or attenuation of cardiac hypertrophy and fibrosis, but did increase plasma ANP and blunted the reactive rise in renin with ACE inhibition. Further studies are needed to determine whether more complete blockade of the renin-angiotensin system with dual NEP/ACE inhibition results in additional benefits in terms of morbidity and mortality in cardiovascular disease.

Vasopressin receptor antagonism--a therapeutic option in heart failure and hypertension

The precise role of vasopressin in the pathophysiology of cardiovascular disease is controversial, but this peptide hormone is important for several reasons. Firstly, circulating concentrations of vasopressin are elevated in heart failure and some forms of hypertension. Secondly, there is evidence that vasopressin is synthesized not only in the hypophysial-pituitary axis but also in peripheral tissues including the heart where it acts as a paracrine hormone. Thirdly, vasopressin has vasoconstrictor, mitogenic, hyperplastic and renal fluid retaining properties which, by analogy with angiotensin II, may have deleterious effects when present in chronic excess. Finally, the availability of orally active non-peptide vasopressin receptor antagonists allows vasopressin receptor antagonism to be considered as a therapeutic option in cardiovascular disease.

Passive ventricular constraint amends the course of heart failure: a study in an ovine model of dilated cardiomyopathy

OBJECTIVE

Dilated cardiomyopathy (DCM) is associated with a progressive deterioration in cardiac function. We hypothesised that some of the deleterious effects of DCM could be reduced by mechanically limiting the degree of cardiac dilatation.

METHODS

A Transonic 20A cardiac output (CO) flow-probe was implanted in the pulmonary artery of 12 adult (52 +/- 4 kg) sheep. Early heart failure was created by rapid right ventricular (RV) pacing for 21 days at a rate which resulted in an initial 10% decrease in CO (to a maximum of 190 bpm). A custom polyester jacket (Acorn Cardiovascular, St Paul, MN) was then placed, via a partial lower sternotomy, on the ventricular epicardium of all sheep. Animals were randomised either to jacket retention (wrap) or removal (sham). Pacing was recommenced at a higher rate (that initiated a further 10% decrease in CO) for 28 days. Haemodynamic and echocardiographic parameters were determined at baseline, implant and at termination.

RESULTS

At termination, the left ventricular fractional shortening was significantly higher (p = 0.03), the degree of mitral valve regurgitation lower (scaled 0-3) (p = 0.03) and the left ventricular long axis area smaller (p = 0.02) in the wrap animals compared with sham.

CONCLUSIONS

In this model of heart failure, ventricular constraint with a polyester jacket diminished the deterioration in cardiac function associated with progressive dilated cardiomyopathy. These results suggest that maintainance of a more normal cardiac size and shape may be beneficial in patients with dilated cardiomyopathy.

Pustular vasculitis of the hands

A case of pustular vasculitis of the hands with evidence of systemic involvement is described. A 64-year-old woman presented with a 2-day history of large, tense bullae arranged symmetrically over the dorsum of the three radial digits and extending on to the radial aspect of the dorsum of each hand. The bullae caused some discomfort and prevented normal use of her hands. There was no response to antibiotic therapy initiated prior to referral to hospital. Initial investigations revealed a raised white cell count with a neutrophilia, a raised erythrocyte sedimentation rate and a raised C-reactive protein. Abnormalities of liver function were detected. Aspirates from the bullae and blood cultures were sterile. The histology of debrided tissue demonstrated a florid neutrophilic dermal infiltrate with many blood vessels associated with prominent fibrin. A diagnosis of pustular vasculitis of the hands was made. The bullae were surgically debrided and treatment with oral corticosteroids was started. Two days after commencement of oral prednisolone, a crusted pustule appeared on her upper cutaneous lip. There was rapid resolution of both the vasculitis of the hands and the pustule on her upper lip following an increase in the dose of oral prednisolone. The patient was discharged on the seventeenth day following admission.

In vivo and in vitro characterisation of a nonpeptide vasopressin V(1A) and V(2) receptor antagonist (YM087) in the rat

This paper reports the in vitro and in vivo characterisation of a nonpeptide, orally active, vasopressin V(1A) and V(2) receptor antagonist, YM087 (methyl-1,4,5,6-tetrahydroimidazo[4, 5-d][1]benzoazepine-6-carbonyl)-2-phenylbenzanilide monohydrochloride) in the rat. YM087 dose dependently displaced the vasopressin V(1A) receptor antagonist radioligand, 125I-labelled [d(CH(2))(5),sarcosine(7)]vasopressin at vasopressin V(1A) receptors in liver and kidney medulla membranes and caused a concentration dependent displacement of the vasopressin V(2) receptor antagonist radioligand [3H]desGly-NH(2)(9)[d(CH(2))(5), D-Ile(2), Ile(4)]vasopressin at vasopressin V(2) receptors in kidney medulla membranes. In vitro binding kinetic studies showed YM087 acted as a competitive antagonist at liver V(1A) and kidney V(1A) and V(2) vasopressin receptors. Oral administration of YM087 (0.1-3 mg/kg) dose dependently inhibited vasopressin binding to liver V(1A) and kidney V(1A) and V(2) vasopressin receptors over 24 h. Oral YM087 (1-3 mg/kg/day) for 7 days in normotensive rats caused a dose dependent aquaresis with no effect on systolic blood pressure. These results show that YM087 is an orally effective vasopressin V(1A) and V(2) receptor antagonist that may be useful in the treatment of conditions characterised by vasoconstriction and fluid retention such as congestive heart failure.

Localization of the insulin-like growth factor system in a rat model of heart failure induced by myocardial infarction

Although cardiac effects of growth hormone (GH) and insulin-like growth factor (IGF)-I have been reported in experimental models of heart failure and in human dilated cardiomyopathy, the IGF system has not been comprehensively assessed in the failing heart. We therefore localized the IGF system in the left ventricle during congestive heart failure after myocardial infarction (MI) in the rat. The left anterior descending coronary artery was ligated in adult female Sprague-Dawley rats and hearts were examined after 6 months when congestive heart failure had developed. In situ hybridization histochemistry was used to localize mRNA for the components of the IGF system in the left ventricle of sham and congestive heart failure animals. We were able to detect changes in the spatial distribution of mRNA for IGF-I and IGF binding proteins 3, 4, 5, and 6 in the left ventricle during congestive heart failure after MI. IGF-I and the binding proteins were predominantly increased in the infarct/peri-infarct area of the left ventricle. Other components of the IGF system were indistinguishable from the low to undetectable levels in sham-operated rats. These results demonstrate that the IGF system is altered in the failing heart and suggest that the IGF system plays an important role in the response of the heart to MI and consequent failure.

Vasopressin V2 receptor enhances gain of baroreflex in conscious spontaneously hypertensive rats

The aim of the present study was to determine the receptor subtype involved in arginine vasopressin (AVP)-induced modulation of baroreflex function in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats using novel nonpeptide AVP V1- and V2-receptor antagonists. Baroreceptor heart rate (HR) reflex was investigated in both SHR and WKY rats which were intravenously administered the selective V1- and V2-receptor antagonists OPC-21268 and OPC-31260, respectively. Baroreflex function was assessed by obtaining alternate pressor and depressor responses to phenylephrine and sodium nitroprusside, respectively, to construct baroreflex curves. In both SHR and WKY rats baroreflex activity was tested before and after intravenous administration of vehicle (20% DMSO), OPC-21268 (10 mg/kg), and OPC-31260 (1 and 10 mg/kg). Vehicle did not significantly alter basal mean arterial pressure (MAP) and HR values or baroreflex function in SHR or WKY rats. The V1-receptor antagonist had no significant effect on resting MAP or HR values or on baroreflex parameters in both groups of rats, although this dose was shown to significantly inhibit the pressor response to AVP (5 ng iv; ANOVA, P < 0.05). In SHR but not WKY rats the V2-receptor antagonist significantly attenuated the gain (or slope) of the baroreflex curve (to 73 +/- 3 and 79 +/- 7% of control for 1 and 10 mg/kg, respectively), although AVP-induced pressor responses were also attenuated with the higher dose of the V2-receptor antagonist. These findings suggest that AVP tonically enhances baroreflex function through a V2 receptor in the SHR.

Clinical management of carpal tunnel syndrome: a 12-year review of outcomes

Carpal tunnel syndrome (CTS) is a disorder frequently encountered by occupational health care specialists. The health care management of this disorder has involved a diverse set of clinical procedures. The present article is a review of the literature related to CTS with an emphasis on occupational-related CTS. MEDLINE, Cumulative Index to Nursing and Allied Health Literature, PsycLIT, and NIOSHTIC databases from 1985-1997 were searched for treatment outcome studies related to CTS. Treatments of interest included surgery, physical therapy, drug therapy, chiropractic treatment, biobehavioral interventions, and occupational rehabilitation. A systematic review of the effects of these interventions on symptoms, medical status, function, return to work, psychological well-being, and patient satisfaction was completed. Compared to other treatments, the majority of studies assessed the effects of surgical interventions. Endoscopic release was associated with higher levels of physical functioning and fewer days to return to work when compared to open release. Limited evidence indicated: 1) steroid injections and oral use of B6 were associated with pain reduction; 2) in comparison to splinting, range of motion exercises appeared to be associated with less pain and fewer days to return to work; 3) cognitive behavior therapy yielded reductions in pain, anxiety, and depression; and, 4) multidisciplinary occupational rehabilitation was associated with a higher percentage of chronic cases returning to work than usual care. Workers' compensation status was associated with increased time to return to work following surgery. Conclusions are preliminary due to the small number of well-controlled studies, variability in duration of symptoms and disability, and the broad range of reported outcome measures. While there are several opinions regarding effective treatment, there is very little scientific support for the range of options currently used in practice. Despite the emerging evidence of the multivariate nature of CTS, the majority of outcome studies have focused on single interventions directed at individual etiological factors or symptoms and functional limitations secondary to CTS.

Salt induces myocardial and renal fibrosis in normotensive and hypertensive rats

BACKGROUND

The detrimental effects of high dietary salt intake may not only involve effects on blood pressure and organ hypertrophy but also lead to tissue fibrosis independently of these factors.

METHODS AND RESULTS

The effect of a normal (1%) or high (8%) sodium chloride diet on myocardial and renal fibrosis was assessed by quantitative histomorphometry in spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto rats (WKYs). The effect of salt on transforming growth factor-beta1 (TGF-beta1) gene expression was assessed by Northern blot hybridization. A high-salt diet from 8 to 16 weeks of age resulted in increased blood pressure and left ventricular and renal hypertrophy in both WKYs and SHRs. Marked interstitial fibrosis was demonstrated in the left ventricle (LV), glomeruli, and renal tubules and in intramyocardial arteries and arterioles but not in the right ventricle. The collagen volume fraction increased significantly after high-salt diet in the LV, intramyocardial arteries and arterioles, glomeruli, and peritubular areas in both WKYs and SHRs. In the kidneys, glomerular and peritubular type IV collagen was also increased. There was overexpression of TGF-beta1 mRNA in the LV and kidneys in both rat strains after a high-salt diet (all P<0.001).

CONCLUSIONS

High dietary salt led to widespread fibrosis and increased TGF-beta1 in the heart and kidney in normotensive and hypertensive rats. These results suggest a specific effect of dietary salt on fibrosis, possibly via TGF-beta1-dependent pathways, and further suggest that excessive salt intake may be an important direct pathogenic factor for cardiovascular disease.

Dual inhibition of neutral endopeptidase and angiotensin-converting enzyme in rats with hypertension and diabetes mellitus

It has been suggested that combined inhibition of angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) may lower blood pressure more effectively than either treatment alone, independent of the degree of salt and volume status or the activity of the renin-angiotensin system. The effects of NEP inhibition in hypertension associated with diabetes mellitus are largely unknown. We therefore compared ACE inhibition, NEP inhibition, and dual NEP/ACE inhibition in diabetic hypertensive rats. Spontaneously hypertensive rats (SHR) aged 9 to 10 weeks were injected with either streptozotocin (45 mg/kg) or citrate buffer and randomized to receive either the ACE inhibitor captopril (25 mg/kg BID), the NEP inhibitor SCH 42495 (30 mg/kg BID), the dual NEP/ACE inhibitor S 21402 (25 or 50 mg/kg BID), or vehicle by gavage for 4 weeks. A group of diabetic SHR was also allocated to receive the combination of SCH 42495 (30 mg/kg BID) and captopril (25 mg/kg BID). The degree of renal NEP inhibition was determined by autoradiography, and plasma renin activity (PRA) was determined by radioimmunoassay. In diabetic SHR, the dual NEP/ACE inhibitor (50 mg/kg BID), as well as the combination of the NEP inhibitor and the ACE inhibitor, reduced systolic blood pressure more effectively than the ACE inhibitor (P<0.001) or the NEP inhibitor (P<0.001) alone. In nondiabetic SHR, the dual NEP/ACE inhibitor and the ACE inhibitor were equally effective, while the NEP inhibitor had only slight blood pressure lowering effects. Relative heart weight decreased in parallel to the changes in blood pressure. Renal NEP was clearly inhibited (70% to 92%; P<0.001) by both the NEP inhibitor and the dual NEP/ACE inhibitor. Both the ACE inhibitor and the dual NEP/ACE inhibitor increased PRA, but the stimulating effect of dual NEP/ACE inhibition on PRA was less than that observed with ACE inhibition alone (P<0.05). Albuminuria in diabetic SHR was lower during treatment with both the dual NEP/ACE inhibitor (50 mg/kg BID) and the combination of NEP inhibition and ACE inhibition compared with vehicle treatment (P<0.05). In conclusion, the present study shows that hypertension in SHR with streptozotocin-induced diabetes is modulated by natriuretic peptides and thus is sensitive to NEP inhibition. The increased efficacy of dual NEP/ACE inhibition on blood pressure in diabetic SHR, compared with ACE or NEP inhibition alone, suggests that this therapeutic approach may prove beneficial in the treatment of hypertension associated with diabetes mellitus and other forms of volume-dependent hypertension.

Long-term effects of nonpeptide vasopressin V2 antagonist OPC-31260 in heart failure in the rat

The hormone arginine vasopressin (AVP) contributes to water retention and vasoconstriction in congestive heart failure (CHF) through effects at the V2 and V1a receptors, respectively. The effect of long-term V2 receptor (V2R) blockade using OPC-31260 was assessed in a rat model of postinfarction-induced CHF. Rats underwent coronary artery ligation or sham operation and were treated for 6 mo with oral OPC-31260 (10 mg . kg-1 . day-1) or vehicle. CHF was characterized by left ventricular remodeling and impaired systolic function, increased cardiac and lung weight, and elevated plasma atrial natriuretic peptide; plasma AVP and plasma renin activity were not increased. Chronic V2R blockade increased urine volume (P < 0.01) and decreased urine osmolality (P < 0.01) but had no natriuretic effects. V2R blockade did not activate the renin-angiotensin system but increased plasma AVP in CHF (P < 0.01). V2R blockade did not influence cardiac remodeling, cardiac function, or survival. These results suggest that AVP plays a major role in water retention through the renal V2R in a rat model of CHF. V2R blockade using OPC-31260 may represent an alternative to standard diuretic therapy in the management of water retention that characterizes heart failure.

Occupational upper extremity disorders in the federal workforce. Prevalence, health care expenditures, and patterns of work disability

Upper extremity disorders (UEDs) account for a significant number of work-related illnesses in the US workforce. Little information exists on the distribution of UEDs, their associated health care and indemnity costs, or patterns of work disability. The study presented is an analysis of upper extremity claims within the federal workforce. In this study, the universe consisted of all claims accepted by the US Department of Labor, Office of Workers' Compensation Programs (OWCP), from October 1, 1993, through September 30, 1994. A total of 185,927 claims of notices of injury were processed during the study period, and of these, 8,147 or 4.4% had an UED diagnosis coded according to the International Classification of Diseases, Clinical Modification (ICD-9-CM). 5,844 claims involved a single UED diagnosis and were the only claims field by these employees between October 1, 1990, and September 30, 1994. These single claims with single diagnoses comprised the sample for further analysis. Mononeuritis and enthesopathies of the upper limb were the most common diagnoses, accounting for 43% and 31% of the claims, respectively. Women had a higher proportion of carpal tunnel syndrome, "unspecified" mononeuritis, and "unspecified" enthesopathies. The majority of claimants for both the mononeuritis- and enthesopathy-related diagnoses were between 31 and 50 years of age, received only health care benefits, and did not incur wage loss. Health care costs for mononeuritis and enthesopathy claims were $12,228,755 (M = $2,849). Carpal tunnel syndrome (CTS) and enthesopathy of the elbow were the most costly diagnoses, accounting for 57% and 16% of the total, respectively. Surgical services represented the highest expenditures in CTS claims. Physical therapy accounted for the majority of health care costs for enthesopathy cases. The mean number of workdays lost for CTS and enthesopathy claims were 84 and 79, and the average indemnity costs were $4,941 and $4,477, respectively. These findings indicate that while UEDs represent a relatively small percentage of all workers' compensation cases, the health care and indemnity costs are considerable. Also mean duration and pattern of work disability revealed that these disorders can result in chronic work disability similar to that observed in low back pain. The results highlight the need to determine whether interventions that account for the majority of costs significantly impact long-term outcomes. There is also a need to identify risk factors for prolonged disability in those who experience problems with delayed recovery.

Vasopressin V1a and V2 receptor mRNA in deoxycorticosterone acetate-salt hypertension in the rat

1. Vasopressin V1a and V2 receptors are differentially regulated in deoxycorticosterone acetate-salt hypertension. This paper investigated whether the changes were due to transcription changes in receptor mRNA assessed by in situ hybridization histochemistry (liver V1a receptor) and by reverse transcription-polymerase chain reaction (kidney V1a and V2 receptor). 2. Systolic blood pressure and plasma vasopressin levels were significantly elevated in deoxycorticosterone acetate-salt rats (n = 24) compared with water-control (n = 28) and salt-control rats (n = 28) (P < 0.001). Plasma sodium was elevated in deoxycorticosterone acetate-salt rats compared with both control groups (P < 0.01) and plasma osmolality was elevated in deoxycorticosterone acetate-salt rats compared with water-control rats (P < 0.05). 3. Binding kinetic studies demonstrated downregulation of liver V1a and kidney V2 receptors in deoxycorticosterone acetate-salt rats compared with water-control and salt-control rats (P < 0.05). This was not associated with any change in liver V1a receptor mRNA (P = 0.95), or in kidney V1a (P = 0.79) or V2 receptor mRNA (P = 0.96). 4. In deoxycorticosterone acetate-salt hypertension, downregulation of liver V1a and kidney V2 receptors occurs in the setting of stable vasopressin gene transcription. These results suggest that changes in receptor processing may be responsible for the differential regulation of vasopressin receptors that occurs in deoxycorticosterone acetate-salt hypertension.

New hormonal blockade strategies in cardiovascular disease

The circulation is controlled by overlapping haemodynamic, structural and neurohumoral mechanisms. Many hormonal vasoactive substances, mostly derived from endothelial cells, are also growth regulators. Although neurohormonal systems are involved in normal physiological compensatory responses they often become maladaptive in conditions such as congestive heart failure. The success of blocking the renin angiotensin system by angiotensin converting enzyme (ACE) inhibitors has led to efforts to block other hormonal systems. Neutral endopeptidase (NEP), the major enzymatic pathway for degradation of natriuretic peptides, has a similar catalytic site to ACE. This has led to compounds that simultaneously inhibit both enzymes. Such dual ACE/NEP inhibitors show promise in experimental hypertension and heart failure. Similar dual NEP/ECE (endothelin converting enzyme) inhibitors are becoming available. The hormone vasopressin has dual actions on the vasculature and the kidney via specific membrane receptors. Specific orally active vasopressin receptor antagonists have been developed and their therapeutic potential in hypertension, heart failure and oedematous states are being explored.

High-dose cyclophosphamide, etoposide and carboplatin with autologous bone marrow support for metastatic breast cancer: long-term results

We report long-term results of high-dose cyclophosphamide, etoposide and carboplatin with ABMT in 20 patients with metastatic breast cancer. Median age of the group was 41 years, ECOG performance status = 0 in 18 patients and 1 in two patients. Twelve patients had received adjuvant chemotherapy. Predominant sites of metastases were lung (eight), chest wall (four), liver (four), bone (three) and lymph nodes (three). Response to pretransplant chemotherapy was complete (CR) in four patients, partial (PR) in 10 patients and stable (SD) in five patients. After high-dose chemotherapy eight patients were in CR, six PR, four SD and one progressive disease. Two patients died of regimen-related toxicities (candidal sepsis and alveolar hemorrhage). With a median follow-up period of 55 months (minimum 48 months), 12 patients have died of recurrent breast cancer, one died of toxicity of salvage chemotherapy, two are alive with disease, two are alive and free of progressive disease. One patient with relapsed disease was lost to follow-up. Median event-free survival is 6 months and median overall survival is 17 months. All three of the long-term disease-free survivors had predominantly nodal disease. Two of these three patients presented with metastatic disease and received high-dose chemotherapy with ABMT as part of initial therapy for breast cancer; two of three attained CR to standard-dose cytoreductive therapy; none received doxorubicin-containing adjuvant chemotherapy.

Susceptibility to atrial fibrillation: a study in an ovine model of pacing-induced early heart failure

INTRODUCTION

The development of susceptibility to atrial fibrillation (AF) is a common consequence of many forms of cardiovascular disease, especially heart failure. In this study we used a sheep model of pacing-induced stable early heart failure to describe, quantify, and relate the level of susceptibility to AF to changes in structural and electrophysiologic parameters.

METHODS AND RESULTS

Epicardial electrodes were implanted on the atria and right ventricles of nine sheep. The AF threshold, atrial vulnerability period, atrial effective refractory period (ERP), and interatrial conduction time were examined during control and over a 6-week period of ventricular pacing at 190 beats/min. Left atrial (LA) area and left ventricular (LV) fractional shortening were monitored using echocardiography. There were significant increases in LA susceptibility to AF (P < 0.0003), LA area (P < 0.0002), and LA ERP400 (P < 0.0002). Rate of increase in LA area was related positively to AF susceptibility (P = 0.02) and inversely to LA ERP400 (P = 0.002). LV fractional shortening decreased to approximately 50% of control value (P < 0.00001). No changes were observed in right atrial electrophysiology.

CONCLUSION

In this study, susceptibility (the ability of an extrastimulus to induce AF) was rigorously measured within a predetermined format. Significant relationships were found to exist between susceptibility, certain of the observed changes in atrial electrophysiology and structure.

Rationale and pharmacology of angiotensin II receptor antagonists: current status and future issues

BACKGROUND

The renin-angiotensin system consists of a cascade of substrate-enzyme interactions that culminates with the production of angiotensin II, the active peptide responsible for all the known effects of the renin-angiotensin system. Blocking this enzymatic cascade has been the focus of considerable research to the extent that the renin-angiotensin system is implicated in the control of blood pressure, sodium and water homeostasis, and cardiovascular function and structure.

ANGIOTENSIN CONVERTING ENZYME INHIBITORS

Angiotensin converting enzyme (ACE) inhibitors provide one way of blocking the renin-angiotensin system, and to this end the compounds have proved efficacious in the treatment of hypertension and cardiovascular disease. However, these compounds are limited in the extent to which they block the renin-angiotensin system, partly due to recently described alternate pathways for the genesis of angiotensin II and also because ACE is not a very specific enzyme and has multiple other potential substrates including bradykinin, tachykinins, neurotensin substance P, and others.

ANGIOTENSIN II RECEPTORS

The development of angiotensin II receptor antagonists represents a new way to block the renin-angiotensin system at the receptor level. Irbesartan is a new angiotensin II receptor antagonist that provides specific and insurmountable antagonism of the AT1 receptor subtype, demonstrating a greater than 8500-fold specificity for the AT1 receptor, the subtype which mediates all the known actions of angiotensin, compared to the AT2 receptor. Comparative studies have demonstrated that irbesartan is 10 times more potent than losartan and slightly more potent than E3174, losartan's active metabolite. Preclinical pharmacological studies in a variety of animal models have demonstrated that irbesartan provides a dose-dependent, insurmountable blockade of angiotensin and reductions in blood pressure, urinary protein and glomerular sclerosis score.

Inhibition of neutral endopeptidase, the degradative enzyme for natriuretic peptides, in rat kidney after oral SCH 42495

1. Inhibition of neutral endopeptidase (NEP), the degradative enzyme for atrial natriuretic peptide, was studied in vitro and in vivo using a previously characterized NEP inhibitor radioligand, 125I-labelled RB104. 2. SCH 42354, the active di-acid of the ethylester prodrug, SCH 42495, caused a concentration-dependent displacement of 125I-labelled RB104 from rat renal NEP. The concentration of SCH 42354 that displaced 50% of radioligand bound to the enzyme NEP (IC50) was 3.3 +/- 0.1 nmol/l (mean +/- SEM). Enalaprilat, an angiotensin converting enzyme inhibitor, did not displace 125I-labelled RB104 in concentrations up to 10 mumol/l. 3. In adult normotensive Sprague-Dawley rats, oral SCH 42495 (3-300 mg/kg) caused significant inhibition of renal NEP (P < 0.001). SCH 42495 had no effect on renal or plasma angiotensin converting enzyme activity, but high-dose SCH 42495 (300 mg/kg) caused a significant increase in plasma renin activity (P < 0.01). 4. In a time course study, oral SCH 42495 (30 mg/kg) caused rapid (within 30 min) and significant inhibition of renal NEP for up to 48 h (P < 0.001). No changes in plasma atrial natriuretic peptide or plasma angiotensin converting enzyme activity were seen. 5. These data provide evidence that short-term administration of the NEP inhibitor SCH 42495 results in inhibition of renal NEP and does not inhibit the circulating or the tissue renin-angiotensin system. The NEP inhibitor radioligand 125I-labelled RB104, is a useful tool to study tissue NEP inhibition after administration of NEP inhibitors.

Chronic vasopressin antagonism in two-kidney, one-clip renovascular hypertension

The role of vasopressin (AVP) in the maintenance of hypertension in the rat model of two-kidney, one-clip (2K1C) Goldblatt hypertension was assessed using the nonpeptide orally effective V1a receptor antagonist, OPC-21268. Rats were studied eight weeks after surgery when mean arterial pressure (MAP) was significantly increased in 2K1C rats compared to SHAM operated controls (2K1C 139 +/- 6, SHAM 106 +/- 3, P < 0.01). Neither acute (OPC-21268, 30 mg/kg) nor chronic (OPC-21268, 30 mg/kg twice daily) V1a receptor blockade reduced blood pressure in either 2K1C or SHAM rats. The results of binding kinetic studies confirmed that OPC-21268 was effective at its putative site of action, the V1a receptor in both 2K1C and SHAM rats. These results indicate AVP is not involved in the maintenance of blood pressure in the 2K1C model of renovascular hypertension.

Angiotensin II receptor antagonists. Potential in elderly patients with cardiovascular disease

Raised blood pressure in the elderly is not a normal consequences of aging, but is a major risk factor for cardiovascular disease. Cardiac and cerebrovascular disease account for > 50% of deaths among people aged > 65 years. Because the percentage of elderly people in most populations is rising, blood pressure control in this group is becoming increasingly important. Several large intervention studies in the elderly have demonstrated that antihypertensive medication reduces cardiovascular morbidity and mortality. In addition, the absolute benefits of blood pressure reduction are higher in elderly compared with younger patients. ACE inhibitors are effective and well tolerated in the treatment of hypertension in the elderly. Their success led to interest in alternative ways of blocking the renin angiotensin system, and the subsequent development of angiotensin II (AII) receptor antagonists. Losartan was the first drug in this class to become commercially available. Since then, valsartan has been launched in some markets and others are likely to be launched in the near future. Losartan is effective in the treatment of essential hypertension and has a low incidence of adverse effects. First-dose hypotension is very uncommon and, at the present time, cough does not appear to be an adverse effect of these drugs, although long term tolerability studies are needed to confirm this. Angioedema, a rare but life-threatening adverse effect of ACE inhibitors, has also been associated with losartan. Current data suggest that All receptor antagonists are effective in elderly hypertensive patients, although further data are needed to confirm these findings. At present, All receptor antagonists are likely to be used in hypertensive patients who are intolerant of ACE inhibitors, although this may change with the availability of long term tolerability and clinical outcomes data.

Elevated vascular angiotensin converting enzyme mediates increased neointima formation after balloon injury in spontaneously hypertensive rats

OBJECTIVE

To measure the effect of hypertension on neointima formation after balloon injury of rat aorta and its association with the local angiotensin converting enzyme (ACE) concentration. Balloon angioplasty of the thoracic aorta using a 2 French Fogarty catheter was performed in spontaneously hypertensive rats (SHR) and normotensive Sprague-Dawley (SD) rats.

RESULTS

The injured aortic wall of SHR had already significantly higher ACE concentrations than did the uninjured aortic wall of normotensive SD rats (media: 729 +/- 37 dpm/mm2 in SHR versus 496 +/- 38 dpm/mm2 in SD rats, P < 0.01; intima: 83 +/- 5 dpm/mm2 versus 68 +/- 6 dpm/mm2 in SD rats, P < 0.01). Fourteen days after injury of the aorta the hypertensive rats had significantly higher neointima: media ratios than did the normotensive rats (0.83 +/- 0.09 versus 068 +/- 0.01, P < 0.01). This was associated with a significant increase in vascular media and neointima ACE concentrations in SHR (media 965 +/- 25 dpm/mm2, neointima 614 +/- 48 dpm/mm2) compared with those in normotensive SD rats after balloon angioplasty (media 669 +/- 23 dpm/mm2, neointima 287 +/- 33 dpm/mm2, P < 0.01). ACE inhibitor treatment with 10 mg/kg body weight lisinopril daily for 14 days by gavage reduced neointima proliferation in hypertensive and normotensive rats (neointima: media ratio: 0.35 +/- 0.02 for SHR, P < 0.01, versus untreated SHR with balloon injury; 0.28 +/- 0.01 for SD, P < 0.01, versus untreated SD rats with balloon injury). This was associated with significant vascular media ACE inhibition (SHR 149 +/- 9 dpm/mm2; SD rats 118 +/- 7 dpm/mm2; P < 0.01 versus untreated controls with balloon injury) and neointima ACE inhibition (SHR 73 +/- 4 dpm/mm2, SD rats 63 +/- 7 dpm/mm2, P < 0.01, versus untreated controls with balloon injury), but also lowered the blood pressure in SHR significantly (to 148 +/- 5 mmHg, P < 0.01, versus untreated SHR with balloon injury). When this drop in blood pressure was prevented by feeding the rats a high-salt diet (SHR with ACE inhibitor plus high salt-diet group blood pressure 193 +/- 3 mmHg, P = 0.57, versus untreated SHR) hypertension per se without the local ACE increase (ACE concentration in SHR with ACE inhibitor high-salt diet rats' media 167 +/- 10 dpm/mm2 and neointima 81 +/- 9 dpm/mm2) had only a mild effect on neointima formation after balloon angioplasty (neointima: media ratio 0.4 +/- 0.01 for SHR with ACE inhibitor plus high-salt diet versus 0.35 +/- 0.02 for SHR with ACE inhibitor plus normal-salt diet P < 0.05). Treatment with 10 mg/kg body weight angiotensin II subtype 1 receptor antagonist losartan potassium daily for 14 days by gavage was associated with a reduction in neointima formation similar to that observed with the ACE inhibitor both for SHR and for SD rats (neointima: media ratio 0.32 +/- 0.04 for SHR with losartan, 0.27 +/- 0.03 for SD rats with losartan; P < 0.01, versus untreated controls with balloon injury) suggesting that ACE inhibitor prevented neointima formation, at least in part by, reducing the local production of angiotensin II.

CONCLUSION

Neointima formation after balloon angioplasty in SHR is increased compared with that in normotensive SD rats. This is due mainly to there being a higher degree of activation of the renin-angiotensin system in the aorta of the SHR before and after balloon injury compared with that in normotensive SD rats measured in terms of the increased vascular ACE concentrations. Blood pressure alone had only a moderate effect on neointima formation.

Diffuse tumor microembolism: a rare cause of a high-probability perfusion scan

Pulmonary tumor embolism is a rare but well-documented cause of respiratory failure in patients with cancer. This entity is probably clinically underrecognized and may represent an important cause of morbidity and mortality. A typical pattern of multiple peripheral subsegmental defects on perfusion lung scanning has been described. We present a case of a unilateral near absence of perfusion in a 53-year-old woman who on autopsy was found to have diffuse tumor microembolism. As new chemotherapeutic agents are developed for the treatment of malignancies, an early diagnosis may become more important. A high-probability perfusion scan should not dissuade the clinician from pursuing further evaluation. Cytologic findings of pulmonary venous blood may be diagnostic.

Angiotensin and bradykinin peptides in rats with myocardial infarction

BACKGROUND

Angiotensin II (Ang II) stimulates cardiac hypertrophy and fibrosis, whereas bradykinin [BK-(1-9)] has cardioprotective actions and reduces infarct size following myocardial infarction.

METHODS AND RESULTS

We investigated whether myocardial infarction and cardiac failure are associated with changes in circulating and tissue levels of angiotensin and bradykinin peptides. Myocardial infarction was produced in rats by coronary artery ligation and confirmed by electrocardiogram. Ang II, Ang I, BK-(1-9), and its metabolite BK-(1-7) were measured 1, 2, 3, 7, and 28 days after myocardial infarction. In comparison with sham operated rats, myocardial infarction reduced blood pressure and body weight, and produced cardiac hypertrophy and cardiac failure. Myocardial infarction increased plasma renin and ACE activity, reduced plasma angiotensinogen, and increased Ang II levels in plasma, aorta, kidney, and lung. Ang II levels in whole cardiac ventricles were similar in infarct and sham operated rats, but were positively correlated with heart weight/body weight ratio in infarct rats 3, 7, and 28 days after infarction. In a separate study of cardiac regions, Ang II levels were similar in infarct and sham operated rats, except at 7 days post surgery when right ventricular Ang II levels were higher in infarct rats. In infarct rats, Ang II levels were higher in the right ventricle and in the infarct than in the non-infarcted left ventricle at 7 days, but these differences were not apparent at 28 days after infarction. BK-(1-9) levels were increased in the heart and lung on days 2 and 3 post infarction, but not in the aorta or kidney. A decrease in BK-(1-7)/BK-(1-9) ratio suggested reduced metabolism of BK-(1-9) to BK-(1-7) in infarcted hearts.

CONCLUSIONS

The transient activation of the circulating renin angiotensin system, and increased Ang II levels in the aorta, kidney, and lung may contribute to the systemic responses to myocardial infarction and cardiac failure. The correlations between cardiac Ang II levels and heart weight/body weight ratio noted for whole cardiac ventricles support a role for local Ang II levels in the process of myocardial remodeling post infarction. The increased cardiac BK-(1-9) levels in the acute phase of myocardial infarction were consistent with a role for this peptide in cardioprotection and limitation of infarct size.

Modulation of genetic hypertension by short-term AVP V1A or V2 receptor antagonism in young SHR

To characterize the role of arginine vasopressin (AVP) V(1A) or V2 receptors and the possible interaction with the renin-angiotensin system in the pathogenesis of hypertension in spontaneously hypertensive rats (SHR), young male SHR were treated from 6 to 10 wk of age with AVP V(1A) receptor blockade, angiotensin-converting enzyme (ACE) inhibition, combination of V(1A) receptor blockade and ACE inhibition, V2 receptor blockade, and vehicle. Treatments were then withdrawn, and systolic blood pressure (SBP) was measured until 19 wk of age. At both 10 and 19 wk of age, SBP was significantly reduced with V(1A) receptor blockade, ACE inhibition, and combined treatment compared with vehicle treatment, although no treatment normalized SBP to levels of Donryu normotensive rats. Throughout the experimental period, no significant additive effects were observed with combined treatment. At 10 wk of age, plasma AVP concentration and 24-h urinary AVP excretion were increased with AVP V2 receptor blockade. At 19 wk of age, SBP was significantly higher in rats previously treated with V2 receptor blockade (233 +/- 3 mmHg) than with vehicle (221 +/- 2 mmHg) (P < 0.01). Left ventricular mass was significantly reduced in rats previously treated with ACE inhibition or combined treatment. These results suggest that AVP (via V(1A) receptors) and angiotensin II contribute to the pathogenesis of SHR hypertension, whereas the AVP V2 receptor may be involved in preventing the full expression of the hypertension, in male SHR.

A risk-benefit assessment of losartan potassium in the treatment of hypertension

Losartan potassium is the first of a new class of orally active antihypertensive drugs which antagonise the action of angiotensin (AT) II at the AT1 receptor subtype. Losartan potassium is converted by the liver to the active metabolite E-3174, which is a more potent antagonist at the AT1 receptor. E-3174 is responsible for most of the pharmacological effects of losartan potassium, and its long half-life contributes to the extended duration of action of the drug. Losartan potassium is effective as a once-daily antihypertensive agent. In mild to moderate hypertension, losartan potassium has similar efficacy to enalapril, atenolol and felodipine extended release. When losartan potassium is combined with hydrochlorothiazide there is a further reduction in blood pressure. Losartan potassium is well tolerated in mild, moderate and severe essential hypertension, with dizziness being reported as the only drug-related adverse effect. The overall rate of patient withdrawal from therapy due to adverse experiences with losartan potassium is lower (2.3%) than that of placebo (3.7%). First-dose hypotension is uncommon, perhaps due to the slower onset of action of the drug, and cough does not appear to be a significant problem. A number of areas concerning the safety and efficacy of losartan potassium remain to be clarified. In particular, long term tolerability studies are needed; cough only became apparent as an adverse effect of ACE inhibitors after 3 to 4 years of use. Postmarketing surveillance has shown that angioedema, a rare but life-threatening adverse effect of ACE inhibitors, also occurs with losartan potassium. Further data are needed on the use of losartan potassium in patients with renal impairment before accepting the recommendation that dosage adjustment is not necessary. The pharmacokinetics and pharmacodynamics of losartan potassium in patients with hepatic disease also require further investigation. Losartan potassium increases uric acid secretion and lowers plasma uric acid levels, which may be of benefit when losartan potassium is combined with a thiazide diuretic, but which may otherwise lead to uric acid stone formation and possibly to nephropathy. Simple control of blood pressure is no longer an adequate goal in the management of hypertension. Any new antihypertensive agent should also reduce cardiovascular events, prevent or cause regression of end-organ damage such as left ventricular hypertrophy, atherosclerosis and renal failure, and should not impair quality of life. Such data on losartan potassium are not currently available. Losartan potassium is likely to be used in patients who are intolerant of ACE inhibitors, but its future in the management of hypertension will depend on long term tolerability studies and data on its effects beyond simple blood pressure control.

Effects of angiotensin-converting enzyme inhibition on angiotensin and bradykinin peptides in rats with myocardial infarction

Angiotensin-converting enzyme (ACE) inhibitors reduce myocardial remodeling and improve cardiac function after myocardial infarction. We investigated whether the beneficial effects of ACE inhibition were associated with changes in the levels of angiotensin and bradykinin peptides in blood, heart, lung, aorta, and kidney. Rats subjected to coronary artery ligation and selected by ECG criteria to have moderate to large myocardial infarctions (mean size, 38%) were administered perindopril (0, 20, 200, and 2,000 micrograms/kg/day) in their drinking water from the second day after surgery for 26 days. Perindopril caused a dose-related decrease in blood pressure and inhibited the development of both cardiac hypertrophy (estimated by heart weight/body weight ratio) and cardiac failure (estimated by lung weight/body weight ratio). Perindopril inhibited plasma ACE activity and increased plasma renin, with an associated decrease in plasma angiotensinogen. Plasma and all tissues showed a marked reduction in angiotensin II/angiotensin I ratio, indicating effective inhibition of ACE in plasma and tissues. Whereas heart, lung, and kidney showed dose-related decreases in angiotensin II (Ang II) levels, plasma and aortic levels of Ang II were not altered by perindopril. Perindopril increased blood bradykinin levels but did not increase bradykinin levels in heart, lung, aorta, or kidney. Heart showed a 45% increase in bradykinin levels at the highest dose of perindopril, which did not achieve statistical significance, although perindopril reduced the bradykinin(1-7)/ bradykinin-(1-9) ratio in heart, indicating inhibition of cardiac metabolism of bradykinin by perindopril. By contrast, perindopril reduced bradykinin levels in lung. These data support a role for reduced blood pressure and cardiac Ang II levels in mediating the effects of ACE inhibition after myocardial infarction but do not support a role for tissue bradykinin in this process.

Validation of an echocardiographic assessment of cardiac function following moderate size myocardial infarction in the rat

1. The present study determined whether two dimensional guided M-mode echocardiography could assess left ventricular (LV) geometry and function following a moderate size myocardial infarction in the rat. 2. Myocardial infarction (MI) was induced by left coronary artery ligation and rats were studied 4 weeks later. Infarct rats showed increased LV internal diastolic diameter (7.33 +/- 0.8 vs 5.91 +/- 0.6 mm; P < 0.001), LV systolic diameter (3.73 +/- 1.2 vs 1.87 +/- 0.6 mm; P < 0.001) and thickening of the noninfarcted posterior wall compared with sham operated rats (1.81 +/- 0.2 vs 1.47 +/- 0.3; P < 0.001; n = 10/group; mean +/- s.d.). Systolic function was impaired in infarct rats who showed reduced fractional shortening (50 +/- 12 vs 68 +/- 9%; P < 0.001) and fractional area change (41 +/- 14 vs 78 +/- 5%; P < 0.001). Infarct size measured echocardiographically was comparable to that measured by quantitative histological examination (29 +/- 10 vs 28 +/- 5%; NS). 3. The present study indicates that postinfarction remodelling leading to LV cavity dilation, hypertrophy of surviving myocardium and impaired systolic function is apparent 4 weeks following moderate size MI in the rat. 4. Transthoracic echocardiography is a noninvasive technique that may be used to assess serially the efficacy of therapeutic interventions designed to prevent remodelling in moderate size MI in the rat.

Differential effects of a novel non-peptide endothelin receptor antagonist (bosentan) in rat liver and vasculature

1. We studied the effects of the non-selective, non-peptide, orally active endothelin (ET) receptor antagonist bosentan (Ro 47-0203) on rat hepatic and mesenteric vascular membrane 125I-ET-1 binding characteristics in vitro and ex vivo (after bosentan by gavage in vivo). 2. Bosentan caused a concentration-dependent competitive inhibition of 125I-ET-1 binding to female rat mesenteric vascular (predominantly ETA receptors) and hepatic (predominantly ETB receptors) membranes in vitro and ex vivo. 3. The time course of the inhibition of binding ex vivo after administration of bosentan in vivo was 1-4h for mesenteric vascular (predominantly ETA receptors) binding and 1-16h for hepatic (predominantly ETB receptors) binding. 4. The time course of displacement of 125I-ET-1 binding from mesenteric vascular and hepatic membranes by bosentan in vitro was similar. 5. Since bosentan is significantly excreted by the liver, the prolonged hepatic 125I-ET-1 binding by bosentan presumably represents hepatic accumulation of bosentan, which may have implications for bosentan antagonizing the actions of ET in the liver.

Potent inhibitory effect of SR 49059, an orally active non-peptide vasopressin VIa receptor antagonist, on human arterial coronary bypass graft

1. The effect of vasopressin receptor antagonists varies between analogues (peptide, non-peptide) and across species. In this study the effect of the novel non-peptide vasopressin V1a receptor antagonist SR 49059 on human internal mammary arteries was investigated. 2. SR 49059 produced a potent, concentration-dependent, inhibitory effect on vasopressin-induced contraction of human coronary bypass graft internal mammary arteries. Both SR 49059 (1 mumol/l) and a peptide selective V1a antagonist ([d(CH2)5sarcosine7]arginine vasopressin) (1 mumol/l) abolished vasopressin-induced contraction. The non-peptide V1a receptor antagonist OPC-21268 (1 mumol/l) had no effect on vasopressin-induced contraction. 3. The effect of SR 49059 was specific to vascular vasopressin receptors as noradrenaline-induced contraction was not influenced by SR 49059. 4. The results of this study in vitro indicate that the non-peptide SR 49059 is a potent, specific vasopressin V1a receptor antagonist in the human internal mammary artery and suggest that it may be a useful tool for studying the pathophysiological role of vasopressin in man.

Attenuation of genetic hypertension after short-term vasopressin V1A receptor antagonism

Abnormalities of the vasopressin system are found in genetic hypertension. This study compares the delayed effects of a brief period of vasopressin V1A receptor blockade and angiotensin-converting enzyme inhibition in young female and male spontaneously hypertensive rats (SHR) on the development of hypertension in adult life. In a separate study, the role of vasopressin in the maintenance of blood pressure in adult SHR was assessed. Young SHR received either the nonpeptide vasopressin V1A receptor antagonist OPC-21268, the angiotensin-converting enzyme inhibitor ramipril, or vehicle from 6 to 10 weeks of age. During the treatment period, OPC-21268 and ramipril reduced systolic blood pressure compared with control SHR (P < .001). Blood pressure in male SHR 7 weeks after treatment withdrawal was 178 +/- 1 mm Hg in ramipril-treated, 184 +/- 1 mm Hg in OPC-21268-treated, and 200 +/- 2 mm Hg in control SHR (P < .001). Similar results were seen in female SHR, although both OPC-21268 and ramipril were less effective antihypertensive agents in female compared with male SHR. The sustained attenuation in blood pressure was not associated with significant cardiovascular structural changes (left ventricular-to-body weight ratio, renal weight-to-body weight ratio, mesenteric resistance artery media-to-lumen ratio). Results of vasopressin V1A receptor binding kinetics and plasma renin or aldosterone concentrations did not suggest a lasting effect of OPC-21268 on the vasopressin system or of ramipril on the renin-angiotensin system following treatment withdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular cloning and sequencing of the gene encoding a sheep arginine vasopressin type 1a receptor

The gene for the sheep arginine vasopressin type 1a (V1a) receptor subtype was cloned from a genomic library. The deduced amino acid sequence shows characteristics of a G-protein coupled receptor and high sequence identity to human and rat V1a receptor sequences (81% and 73%, respectively). Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed a tissue distribution consistent with a type V1a receptor. The genomic DNA (7.1 kb) contains a 1586 bp intron between the putative 6th and 7th transmembrane domains.

Beyond ACE inhibition: new developments in drug therapy for hypertension

The growing list of vasoactive substances known to be involved in blood pressure control provides new targets for antihypertensive drugs. Currently under development are alternative strategies for blockade of the renin-angiotensin system (e.g., renin inhibition and angiotensin II receptor antagonism) that may have fewer side effects than angiotensin-converting-enzyme inhibition, and antagonists to other vasocontrictor peptides, such as endothelin and vasopressin. Novel strategies to enhance the effects of endogenous vasodilators, such as natriuretic peptides and nitric oxide, are also being explored.

Negative regulators may mediate some of the inhibitory effects of HIV-1 infected stromal cell layers on erythropoiesis and myelopoiesis in human bone marrow long term cultures

This report presents results concerning the potential role of negative regulators in hematopoietic suppression observed in human immunodeficiency virus (HIV)-infected long-term cultures (LTC) of human bone marrow cells. Confluent stromal cell layers established from human bone marrow cells were exposed to HIV-1ADA, a monocytotropic strain of HIV-1. A progressive increase in the concentration of HIV-1 p24 antigen in cultures exposed to HIV-1ADA demonstrated that there was a productive infection. Cells from both noninfected and HIV-infected stromal cell layers produced factors that stimulated the proliferation of colony-forming units for granulocytes and macrophages (CFU-GM) from non-infected CD34+ cells. In contrast, when noninfected CD34+ cells were directly cocultured on intact stromal cell layers fewer CFU-GM and burst-forming units for erythroid cells (BFU-E) were detected in HIV-infected LTC than in noninfected LTC. One week after the addition of CD34+ cells, the number of CFU-GM in HIV-infected LTC in six of nine experiments was reduced compared to noninfected control LTC. In those six experiments, the number of CFU-GM was only 53 +/- 5% (SEM) of the number in noninfected LTC. The number of BFU-E in HIV-1-infected LTC was only 46 +/- 5% of the number in noninfected LTC (n = 5). There were fewer BFU-E in HIV-1-infected LTC, whether or not there was a reduced number of CFU-GM. Neutralizing antibody to tumor necrosis factor alpha (TNF-alpha) had no effect on the number of BFU-E in HIV-infected LTC. The number of BFU-E, however, was 2.1 +/- 0.2-fold greater (n = 3) in HIV-infected LTC incubated with neutralizing antibody to interferon-alpha. In HIV-infected LTC with decreased numbers of CFU-GM, the number of CFU-GM was approximately 2-fold greater after incubation of HIV-infected LTC with anti-interleukin-4 (IL-4). The effect of anti-TNF-alpha was variable, and anti-transforming growth factor-beta had no effect on the number of CFU-GM in HIV-infected LTC. After 2 weeks, the number of CFU-GM in HIV-infected LTC incubated with anti-IL-4 and anti-TNF-alpha was 2- to 4-fold greater than in untreated HIV-infected LTC. Antibody treatment did not promote an increase in the number of CFU-GM in noninfected LTC or in LTC in which CFU-GM numbers were not reduced after HIV infection.(ABSTRACT TRUNCATED AT 400 WORDS)