Effects of a xanthine oxidase/hypoxanthine free radical and reactive oxygen species generating system on endothelial function in New Zealand white rabbit aortic rings

We investigated the effects of the xanthine oxidase (XO)/hypoxanthine (HX) free radical (FR) generating system on the relaxant properties of aortic rings from New Zealand White rabbits. This system generates superoxide anions, hydroxyl radicals, and H2O2. We wished to identify which of these species is responsible for impairment of vascular function. After obtaining dose-response curves to phenylephrine (PE) and carbachol or sodium nitroprusside (SNP), we exposed rings to the FR generating system or H2O2 for 30 min, either with or without a range of potentially protective agents. Dose-response curves to carbachol or SNP were then repeated. Exposure to the XO/HX system impaired endothelium-dependent, carbachol-induced relaxation. The hydroxyl radical scavengers mannitol, N-(2-mercaptopropionyl)-glycine (MPG), and captopril offered no protection. Superoxide dismutase (SOD) increased the impairment of response, catalase provided partial protection, and a combination of SOD and catalase completely prevented impairment of the response. H2O2 mimicked the effects of XO/HX system. H2O2 appears to be the primary species involved in mediating the toxic effects of the XO/HX FR generating system, but the superoxide anion is probably responsible for some of the loss of relaxation and a role for intracellular generation of hydroxyl radicals cannot be excluded.

Evidence of oxidative stress in chronic heart failure in humans

Chronic heart failure (CHF) due to coronary artery disease (CAD) has been shown to be associated with increased plasma thiobarbituric reactive substances (TBARS) and reduced plasma thiol (PSH) concentrations, suggesting oxidative stress (OS). The aims of the present studies were (a) to determine whether OS is due to CAD or CHF per se and (b) to determine if a wider range of more specific markers of OS are abnormal in CHF. In the first study, two groups of patients (n = 15 each) were compared. Group 1 (11 male, mean age 56 years) had CHF due to CAD and group 2 (12 male, mean age 53 years) had non-CAD CHF. Median plasma TBARS in controls was 7.6 nmol.ml-1, 10.0 nmol.ml-1 in group 1 and 9.3 nmol.ml-1 in group 2 (P < 0.01 both groups vs control). Median PSH was 505 384 and 364 nmol.ml-1 (P < 0.05 and P < 0.01 vs control) respectively. Fifty-three patients with CHF were recruited in the second study. Malondialdehyde and PSH were 10.3 and 409 nmol.ml-1 respectively, compared to control values of 7.9 and 560 nmol.ml-1 (both P < 0.001). The median values for the following additional measures of OS in controls and patients were: erythrocyte superoxide dismutase 131 vs 114 U.l-1 (P = 0.005); caeruloplasmin oxidase 97 vs 197 U.l-1 (P < 0.01); erythrocyte glutathione 1.56 nmol.ml-1 vs 1.77 nmol.ml-1 (P < 0.02); plasma conjugated dienes 0.28 vs 0.33 optical density units (P = ns).(ABSTRACT TRUNCATED AT 250 WORDS)

Trends in hospitalization for heart failure in Scotland 1980-1990

Heart failure is a growing public health problem in industrialized countries with ageing populations. Scotland has a relatively stable population of approximately 5 million and a well described system for recording details of hospitalizations (Scottish Hospital In-Patients Statistics-SHIPS). We have examined SHIPS data for hospitalizations for heart failure in Scotland 1980-1990. Discharges for heart failure as the primary diagnosis increased by almost 60%, from 1.30 to 2.12/1000 population in this period (as either primary or secondary diagnosis the rate increased from 2.51 to 4.24/1000). Seventy-eight percent of discharges were in persons aged > or = 65 years and 48% of discharges were male. Heart failure (primary diagnosis) accounted for almost 4% of all general (internal) medicine discharges. In-patient case fatality was 18% in 1990. Mean duration of in-patient stay on Internal Medicine wards was approximately 11 days. The number of hospitalizations for heart failure is now almost identical to those for myocardial infarction. These trends mirror those recently reported from the United States. Heart failure is an increasingly common and costly cause of hospitalization in Scotland. Approaches which can reduce this burden on the hospital service require urgent attention.

Effects of the xanthine oxidase system on cardiac function in anaesthetised rats

This investigation aimed to determine whether contractile dysfunction of the myocardium could be produced upon generation of free radicals in the anaesthetised rat. The enzyme xanthine oxidase, combined with its substrate purine and an iron source, was used to generate free radicals in the venous circulation. The suspended form of xanthine oxidase, with substrate, produced a transient, significant depression in the contractile indices dP dt-1 max and dP dt-1 P-1 and arterial blood pressure, 1146 +/- 87 mm Hg s-1, 9 +/- 1 s-1, and 18 +/- 1 mm Hg, respectively. This could not be attenuated by the enzymatic free radical scavengers superoxide dismutase and catalase. Furthermore, the suspended xanthine oxidase alone or its vehicle were able to produce a similar effect to that of the complete free-radical-generating system. The maximum soluble dose of the crystalline form of the enzyme when employed in the generating system had no effect upon administration despite its production of superoxide radicals in vitro. These results suggest that the haemodynamic effects of the free-radical-generating system containing the suspended form of xanthine oxidase were due to the effects of its vehicle and that the free-radical-generating system containing the crystalline form of the enzyme did not produce sufficient free radicals in vivo to modify myocardial contractility.

Evidence for oxidative stress in unstable angina

OBJECTIVE

To determine whether unstable angina, which is characterised by recurring episodes of myocardial ischaemia and reperfusion, is associated with oxidative stress (that is, where there is an imbalance between oxidants, such as free radicals, which are in excess and antioxidants).

DESIGN

Between group comparison of patients with unstable angina, stable angina, and healthy controls.

SETTING

The coronary care unit and cardiac investigation ward of a regional cardiology centre.

PATIENTS

Twenty five consecutive patients admitted to the coronary care unit with unstable angina. Twenty five consecutive patients admitted to the cardiac investigation ward (patients with stable angina undergoing coronary angiography) were used as controls for the presence of atherosclerosis, drug treatment, and smoking habit. Thirty eight healthy controls (hospital staff and patients admitted for minor surgical procedures who were otherwise healthy) were also studied.

MAIN OUTCOME MEASURES

Thiobarbituric acid related substances (TBARS) in plasma and plasma reduced thiol (PSH) as indicators of oxidative damage to lipids and proteins respectively were measured. Coronary angiography was performed in all patients with stable angina and roughly half of those with unstable angina.

RESULTS

Mean (SEM) plasma TBARS in unstable angina and stable angina were 9.95 (0.36) nmol/ml and 9.14 (0.28) nmol/ml respectively (p = 0.08). Mean plasma TBARS in healthy controls were 8.09 (0.21) nmol/ml (p < 0.05 compared with both angina groups). Mean (SEM) PSH concentration in unstable angina was 4.21 (9) nmol/ml and in stable angina was 4.85 (9) nmol/ml (p < 0.05). Mean PSH in healthy controls was 5.64 (8) nmol/ml (p < 0.001 compared with both angina groups). The extent of coronary artery disease, use of medication, and smoking habit were not significantly different between the angina groups.

CONCLUSIONS

Biochemical indicators of oxidative stress are more abnormal in unstable than stable angina. This is in keeping with experimental evidence that episodes of ischaemia and reperfusion lead to generation of free radicals and toxic oxygen species and depression of endogenous antioxidant activity. The clinical significance of this finding remains to be determined, although, experimentally, free radicals and toxic oxygen species have adverse effects on myocardial contractile function, myocardial electrical stability, endothelial mediated vasodilatation, and coagulation.

Practical issues when initiating captopril therapy in chronic heart failure. What is the appropriate dose and how long should patients be observed?

To assess the feasibility of introducing captopril in patients with chronic heart failure on an outpatient rather than an inpatient basis a double-blind placebo-controlled study was carried out to compare either 6.25 mg or 25.0 mg of captopril as a starting dose; followed by either incremental doses of 6.25, 12.5, and 25.0 mg (low dose group), or 25.0 mg 8 hourly (high dose group) respectively. Forty-one patients in a general medical ward within a large teaching hospital with moderate to severe, stable, diuretic-controlled chronic heart failure, who were not hyponatraemic, hypokalaemic or on a dose of diuretic greater than 120 mg of frusemide took part. No patient experienced symptomatic hypotension. Both doses of captopril produced a significant drop in blood pressure (BP), the magnitude of which was similar in both groups. The first dose-induced fall correlated significantly with subsequent dose-related reductions in BP. Therefore if a patient did not have a hypotensive response to the first dose of captopril he/she would be unlikely to have one with subsequent doses. In the group as a whole, the magnitude of the fall in BP after the first dose correlated significantly with starting plasma levels of angiotensin II, atrial natriuretic peptide (ANP), aldosterone, and renin. However, on an individual basis, the two patients with the greatest fall in blood pressure did not have the most activated renin-angiotensin-aldosterone (RAA) system. This serves to emphasise the unpredictability of this response and the need to initiate therapy under clinical observation.(ABSTRACT TRUNCATED AT 250 WORDS)

Antioxidant effects of angiotensin-converting enzyme (ACE) inhibitors: free radical and oxidant scavenging are sulfhydryl dependent, but lipid peroxidation is inhibited by both sulfhydryl- and nonsulfhydryl-containing ACE inhibitors

With an assay that generates free radicals (FR) through photooxidation of dianisidine sensitized by riboflavin, 4 x 10(-5) M captopril, epicaptopril (SQ 14,534, captopril's stereoisomer), zofenopril, and fentiapril [all sulfhydryl (-SH)-containing angiotensin-converting enzyme (ACE) inhibitors] were shown effective scavengers of nonsuperoxide free radicals whereas non-SH ACE inhibitors were not. Captopril was a more effective FR scavenger at pH 5.0 than at pH 7.5. Captopril (2 x 10(-5) M) also scavenged the other toxic oxygen species hydrogen peroxide and singlet oxygen and inhibited microsomal lipid peroxidation. Finally, captopril reduced the amount of superoxide anion-radical detected after neutrophils in whole blood were activated with zymosan, probably by inhibiting leukocyte superoxide production.

Increased concentrations of tumour necrosis factor in "cachectic" patients with severe chronic heart failure

OBJECTIVE

To ascertain whether patients with cardiac failure and reduced body weight ("cardiac cachexia") have increased circulating concentrations of tumour necrosis factor (cachectin).

DESIGN

Patients with cardiac failure were prospectively identified as "cachectic" (body fat less than 27% in men and less than 29% in women measured by skinfold thickness callipers) or "non-cachectic". Tumour necrosis factor was assayed blind to patient group.

SETTING

Cardiology unit in a tertiary referral centre.

PATIENTS

26 consecutive patients (10 women) (mean age 61) admitted for investigation or treatment of chronic heart failure. All were in New York Heart Association class III or IV.

RESULTS

In nine of the 16 cachectic patients the concentration of tumour necrosis factor was increased (mean (SEM) 74 (20) pg/ml) compared with one of the 10 "non-cachectic" patients (22 pg/ml, p less than 0.001). Patients with a raised circulating concentration of tumour necrosis factor weighed significantly less (55.6 (3.5) kg) than those in whom the concentration of tumour necrosis factor was normal (69.0 (4.1) kg) (p = 0.02).

CONCLUSIONS

Circulating concentrations of tumour necrosis factor were increased in a significant proportion of patients with chronic heart failure and low body weight. Tumour necrosis factor stimulates catabolism experimentally and it may be a factor in the weight loss seen in patients with "cardiac cachexia".

Synergism of histidyl dipeptides as antioxidants

Histidyl dipeptides such as carnosine (beta-alanyl-L-histidine) and homocarnosine (gamma-amino-butyryl-L-histidine) are reported at millimolar concentrations in several mammalian tissues (O'Dowd et al., 1988; House et al., 1989), but their precise physiological function, or functions, is uncertain. These compounds are known to be potent buffers at physiological pH (Davey, 1960). They are also able to restore functional capacity to fatigued muscle preparations, stimulate some glycolytic enzymes and maintain coupling between mitochondrial oxidation and phosphorylation (Severin, 1964). Histidyl dipeptides may also have antioxidant activity, though this finding is controversial. For example, Aruoma et al. have argued that these compounds, individually, are unable to scavenge superoxide (O2-.), hydrogen peroxide (H2O2) or hypochlorous acid (HOCl) at rates which could offer antioxidant protection in vivo. Since there is a range of these histidyl dipeptides within mammalian tissue we have investigated possible synergism between them in respect of antioxidant activity. Our results show that combining histidine-containing compounds at near physiological concentrations results in synergistic antioxidant activity.

Effects of xamoterol in acute myocardial infarction: blood pressure, heart rate, arrhythmias and early clinical course

Xamoterol is a novel partial agonist of beta 1 adrenoceptors that reduces myocardial ischaemia and improves ventricular function in patients with mild to moderate heart failure. In a double blind, randomised, placebo controlled study, the effects of xamoterol given in a dose of 200 mg twice daily were studied in 51 consecutive patients with acute myocardial infarction, including 17 receiving diuretics for left ventricular failure. Treatment was started on the third day of admission and continued for 7 days. Blood pressure was recorded at 0900 daily, and 24 hour ambulatory electrocardiogram monitoring was commenced at this time on days 1 (pre-treatment), 4, 6 and 9 of admission. Additional drug therapy was recorded daily throughout the study. One patient died prior to randomisation and three were withdrawn (1 placebo, 2 xamoterol) with ventricular arrhythmias and/or disturbances of conduction. Compared to placebo, xamoterol had no effect on the rate of ventricular premature beats or ventricular tachycardia. Xamoterol increased nocturnal heart rate (0000-0600 hrs 79 +/- 2; placebo 72 +/- beats/min; P less than 0.03) but did not change blood pressure. Three patients receiving xamoterol, and 7 on placebo, required new (after randomisation) antianginal therapy. One patient treated with placebo developed new heart failure. These results show that xamoterol can be administered safely to selected patients following myocardial infarction, including those treated for mild heart failure.

Unique cardioprotective potential of angiotensin converting enzyme inhibitors: a hypothesis still to be tested on humans

'Primary cardioprotection' has, arguably, already been shown with thiazide diuretics and probably with beta-blockers. The proven safety and efficacy of these established drugs override any theoretical or experimental considerations in favour of ACE inhibitors. It is unfortunate that, as yet, the number of hypotheses generated in support of ACE inhibitors has not been matched by large scale clinical trials employing these drugs. The first report of the clinical use of an ACE inhibitor was in 1984; it is high time comparative studies with conventional, and proven, agents were undertaken. With regard to 'secondary cardioprotection', there is overwhelming evidence in favour of the use of beta-blockers in patients with myocardial ischaemia. Indeed, we would argue that ACE inhibitors should be used with caution in such patients to avoid impairment of coronary infusion. In the patient with acute myocardial infarction, intravenous nitrates are cheap, easy to use, safe and seem to be effective (in preventing early remodelling and reducing mortality). In the subacute phase, beta-blockers improve prognosis and, according to the currently available evidence in humans, nitrates are as effective as captopril in altering late remodelling; as in the acute situation, nitrates are cheaper, simpler to use and have a track record of long-term safety. ACE inhibitors improve symptoms, exercise capacity and prognosis in chronic heart failure. In this condition, they have been a major therapeutic advance and, on the available evidence, are to be initially preferred to other vasodilators though they should be given in addition to diuretics.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial natriuretic factor in chronic heart failure

The pathophysiological role of atrial natriuretic factor in patients with chronic heart failure is still unclear. Plasma ANF levels are elevated in this condition, particularly in patients with severe left ventricular dysfunction and during acute exacerbations. Drug therapy, including diuretics, vasodilators and inotropes which reduce cardiac filling pressures also reduce plasma ANF levels. In the clinical setting the measurement of ANF levels may provide a useful means of assessing salt and water retention in patients with heart failure. Intravenous infusion of ANF to patients with heart failure causes a diuresis and natriuresis, a fall in filling pressures and possibly suppression of the renin-angiotensin aldosterone system. High bolus dosing with the peptide may reduce systemic vascular resistance resulting in hypotension, which markedly attenuates the renal effects. A new pharmacological approach in this area is the development of neutral endopeptidase inhibitors, which prolong the half-life of endogenous ANF and potentiate its effects. The therapeutic potential of ANF in heart failure has yet to be realised.

Influence of ACE inhibitors on free radicals and reperfusion injury: pharmacological curiosity or therapeutic hope?

1. The currently available evidence shows that thiol containing ACE inhibitors are free radical (FR) scavengers in vitro; in particular the OH. radical is effectively scavenged by these compounds. There is also good evidence that, in vivo, ACE inhibitors can preserve myocardial contractile function following a period of reversible ischaemia (by directly protecting myocytes and/or preserving coronary flow through protection of endothelial cells). These in vivo benefits are probably also due to FR scavening, mainly due to the presence of a thiol group but, also as a consequence of augmented prostanoid production. 2. Use of more relevant animal models and testing of a range of doses of ACE inhibitors might be undertaken before clinical investigation is considered. Because of its nature, however, the existence and importance of reperfusion injury in man will only be proven or disproven by pharmacological intervention. One option is to compare a thiol containing agent with absent or minimal haemodynamic effects with placebo as an adjunct to thrombolysis. This is the simplest approach. An alternative approach is to conduct a comparative study of a -SH containing ACE inhibitor and a non -SH containing ACE inhibitor given prior to thrombolysis. There are many problems with either approach. The lack of reliable measures of FR activity in man and difficulty in measuring accurately left ventricular function post-myocardial infarction means that mortality is likely to be the only reliable end-point in such a study.(ABSTRACT TRUNCATED AT 250 WORDS)

Free radical scavenging: a potentially beneficial action of thiol-containing angiotensin converting enzyme inhibitors

Free radical (FR) scavenging may be a therapeutically useful adjunctive property of angiotensin converting enzyme (ACE) inhibitors. In this study we have shown that SH-containing ACE inhibitors (captopril, epicaptopril, zofenopril) are potent FR scavengers at a concentration of 4 x 10(-5) M whereas non-SH ACE inhibitors (enalaprilat, quinaprilat and perindoprilat) have no FR-scavenging activity at this concentration. Furthermore, the SH-containing agents preferentially scavenged general radicals rather than superoxide radicals, i.e. suggesting that these drugs would be effective in quenching the culprit FR in ischaemia/reperfusion injury.

Novel exercise protocol suitable for use on a treadmill or a bicycle ergometer

Many exercise protocols are in use in clinical cardiology, but no single test is applicable to the wide range of patients' exercise capacity. A new protocol was devised that starts at a low workload and increases by 15% of the previous workload every minute. This is the first protocol to be based on exponential rather than linear increments in workload. The new protocol (standardised exponential exercise protocol, STEEP) is suitable for use on either a treadmill or a bicycle ergometer. This protocol was compared with standard protocols in 30 healthy male volunteers, each of whom performed four exercise tests: the STEEP treadmill and bicycle protocols, a modified Bruce treadmill protocol, and a 20 W/min bicycle protocol. During the two STEEP tests the subjects' oxygen consumption rose gradually and exponentially and there was close agreement between the bicycle and the treadmill protocols. A higher proportion of subjects completed the treadmill than the bicycle protocol. Submaximal heart rates were slightly higher during the bicycle test. The STEEP protocol took less time than the modified Bruce treadmill protocol, which tended to produce plateaux in oxygen consumption during the early stages. The 20 W/min bicycle protocol does not take account of subjects' body weight and consequently produced large intersubject variability in oxygen consumption. The STEEP protocol can be used on either a treadmill or a bicycle ergometer and it should be suitable for a wide range of patients.

Oxidative damage in chronic heart failure: protection by captopril through free radical scavenging?

The pathogenesis of heart failure is not yet fully understood. In animal models there is some evidence to suggest a role for free radicals (FRs). We have investigated malondialdehyde - LM in plasma of patients with heart failure and found it to be raised when compared to controls. We present data to show that Captopril, a drug with an ACE inhibitory effect is a FR scavenger both in vitro and ex-vivo in patients with heart failure.

Atrial natriuretic factor attenuates prostaglandin E2-stimulated plasma renin activity in humans

The effect of atrial natriuretic factor (ANF) 99-126 3 or 10 pmol/kg/min on increase in plasma renin activity (PRA) stimulated by a 30-min infusion of prostaglandin E2 (PGE2) 80 ng/kg/min was studied in healthy salt-replete male volunteers. PGE2 increased PRA to approximately 230% of basal levels (p less than 0.001). Concomitant infusion of ANF 3 pmol/kg/min significantly attenuated this rise in PRA to approximately 130% of baseline values (p = 0.02, n = 10). A quantitatively similar effect was observed with ANF 10 pmol/kg/min (n = 5). We suggest, in light of previous findings, that this inhibitory effect of ANF probably represents a nonspecific action rather than a specific effect of ANF on PGE2-mediated increases in PRA.

A survey of current use of angiotensin-converting-enzyme inhibitors by Scottish physicians in the treatment of chronic cardiac failure

318 consultant physicians in Scotland were sent a questionnaire on their use of angiotensin converting enzyme (ACE) inhibitors to treat chronic heart failure (CHF). 229 (72%) replies were received. Of these 91% used ACE inhibitors for CHF; 22% were geriatricians, 58% general physicians and 20% cardiologists. All groups reserved ACE inhibitors for patients uncontrolled by diuretics alone. Compared to general physicians, cardiologists used ACE inhibitors in preference to other vasodilators and digoxin, used higher doses and commenced treatment more often on a day-patient basis. Cardiologists also commonly started treatment with captopril even if continuing with enalapril. Geriatricians used ACE inhibitors as frequently as cardiologists but at lower doses; they did not report side-effects more frequently. Further investigation of the safety and possible cost savings of supervised day-patient rather than in-patient, introduction of ACE inhibitors for CHF is now merited. To avoid an extended period of patient observation after the first dose of ACE inhibitor, captopril might also be given as the initial therapy, even if continuing with enalapril. This policy would also reduce the risk of any hypotensive response being prolonged.

Dexamethasone suppression test in dementia and depression. Clinical and biological correlates

To determine the usefulness of the DST in differentiating depression from dementia, the test was administered to three diagnostic groups of psychogeriatric patients: depression; dementia; and dementia with depression. Clinical assessments were supplemented by ratings on the HRSD and SCAG, as well as by EEG and CT. All three groups showed a high incidence of abnormal DST results unrelated to presence or severity of affective symptoms, but showing a better association with SCAG and its 'organic' subsets. The mechanism(s) underlying these abnormal results may reflect organic brain disease. The usefulness of the DST in differentiating depression from dementia in the elderly was not confirmed.

Captopril: a free radical scavenger

The use of captopril in heart failure and hypertension is becoming increasingly accepted. Captopril has a sulphydryl group in its molecular structure. We wondered if this might confer free radical scavenging activity on the drug and have investigated this in an in vitro system. Results show that captopril is a free radical scavenger and we suggest that this action might be relevant in its use in heart failure and other vascular diseases.

Sympathoadrenal responses during bradycardia-hypotension associated with combined infusion of atrial natriuretic factor and prostaglandin E2

The adrenergic response to an episode of bradycardia and hypotension associated with atrial natriuretic factor and prostaglandin infusion in a healthy male subject is described. Noradrenaline levels did not change despite a profound fall in blood pressure. In contrast, there was an almost thirty-fold increase in adrenaline levels. This dissociated sympathoadrenal response suggests activation of the Bezold-Jarisch reflex.

Evidence for a proximal and distal nephron action of atrial natriuretic factor in man

The intrarenal mechanism of action of atrial natriuretic (ANF) remains uncertain. Animal work suggests that part of the natriuretic effect of ANF may be due to inhibition of proximal and distal nephron sodium reabsorption and we now present evidence for similar effects of ANF in man. Six sodium replete normal male volunteers were studied during maximal water diuresis. Lithium clearance was used to assess segmental nephron function. ANF infusion caused a significant increase in fractional lithium clearance (FELi) compared to placebo infusion. A similar change in fractional distal delivery, a conventional marker of proximal tubular outflow, also occurred during ANF infusion independently corroborating the increase in FELi. These findings suggest that ANF inhibits whole-kidney fractional proximal tubular sodium reabsorption in man. Evidence is also presented to show that ANF depresses distal nephron fractional sodium reabsorption as evaluated both by the lithium method and by estimation of solute-free water clearance.

Effects of atenolol, verapamil, and xamoterol on heart rate and exercise tolerance in digitalised patients with chronic atrial fibrillation

The aim of the study was to compare the effects of atenolol (50 mg b.i.d.), verapamil (80 mg b.i.d.), xamoterol (200 mg b.i.d.), and matching placebo on heart rate (HR) and exercise tolerance in digitalised patients with chronic atrial fibrillation. Each treatment was taken for 4 weeks, and digoxin was continued throughout the study. During treatment with placebo (digoxin alone), the mean postexercise heart rate was 164 beats/min, and four subjects had rates of greater than or equal to 170 beats/min. Atenolol, verapamil, and xamoterol achieved significantly better control of exercise-induced tachycardia, mean postexercise heart rates being reduced to 120, 131, and 130 beats/min, respectively (p less than 0.01 for each). However, minimum HRs less than or equal to 45 beats/min occurred during treatment with placebo, atenolol, and verapamil, whereas treatment with xamoterol was associated with a minimum heart rate of 56 beats/min. Treatment with atenolol was associated with a marked reduction in maximum treadmill walking distance (mean 356 m) as compared both with placebo (mean 421 m, p less than 0.01) and verapamil (mean 439 m, p less than 0.01). Xamoterol reduced maximum walking distances as compared with verapamil (402 vs. 439 m; p less than 0.05) but not placebo (402 vs. 421 m; NSS). Thus, atenolol, verapamil, and xamoterol achieved better control of exercise-induced tachycardia than digoxin, but atenolol clearly impaired exercise tolerance whereas verapamil did not. Xamoterol achieved more even control of ventricular response rates and prevented the resting bradycardias that occurred with the other treatments. However, walking distances were significantly lower than those noted during treatment with verapamil.

Arginine vasopressin dissociates the diuresis and natriuresis due to atrial natriuretic factor in man

The possible interaction between arginine vasopressin (AVP) and atrial natriuretic factor (ANF) in the control of urinary sodium and water excretion was investigated in man. Nine healthy male volunteers undergoing stable maximal water diuresis were studied on four separate occasions. Atrial natriuretic factor 15 pmol kg-1 min-1 or placebo (P) was concomitantly administered against a background infusion of either AVP 0.003 pmol kg-1 min-1 or P; thus the combinations P + P, AVP + P, P + ANF and AVP + ANF were studied. Atrial natriuretic factor caused a significant increase in sodium excretion (UNaV) [+56%], urinary flow rate (V) [+17%] and free water clearance (CH2O) [+23%]; creatinine clearance (Ccr) did not change. Arginine vasopressin reduced V (-58%) and CH2O (-68%) but did not alter UNaV or Ccr. On the AVP + ANF study day, UNaV increased (+64%) as with P + ANF, but V (-44%) and CH2O (-52%) continued to decrease below baseline levels; analysis of variance showed this antidiuresis reflected the prevalent effect of AVP rather than any specific interaction. These results show that AVP is able to dissociate the natriuretic and diuretic effects of ANF.

The effect of atrial natriuretic factor on urinary albumin and beta 2-microglobulin excretion in man

The effect of a 20-min infusion of atrial natriuretic factor (ANF) 99-126, 0.4 microgram/kg per min, on both urinary albumin and beta 2-microglobulin excretion was examined in nine normal male subjects during stable water diuresis. ANF caused a rise in urinary albumin in excretion (from 4.19 +/- 0.66 to 13.49 +/- 3.07 ng/min, P less than 0.01) without any significant change in either creatinine clearance of beta 2-microglobulin excretion. These findings suggest that ANF may enhance glomerular permeability to albumin in man.

Significance of atrial natriuretic factor in chronic heart failure

Since the discovery by de Bold et al in 1981 of the natriuretic and diuretic properties of atrial extract a vast literature on the physiological, pharmacological and pathological aspects of atrial peptides has accumulated. In this article we review the significance of atrial natriuretic factor, endogenous and exogenously administered, in chronic heart failure.

Frusemide pretreatment blunts the inhibition of renal tubular sodium reabsorption by ANF in man

The effects of atrial natriuretic factor (ANF) 15 pmol/kg/min on renal function were studied in 7 normal male volunteers during maximal water diuresis. Subjects were studied in neutral salt balance either before, or after, seven days treatment with 40 mg oral frusemide. The post-frusemide state was associated with activation of the renin-angiotensin system (RAAS) and generally higher noradrenaline levels; this state was also associated with sodium retention, mainly due to enhanced distal nephron reabsorption. Without diuretic pretreatment ANF produced a natriuresis and diuresis associated with inhibition of both proximal and distal nephron sodium reabsorption. In contrast, after frusemide pretreatment, ANF caused an increase in water excretion (urinary flow rate) but no change in sodium excretion. In the post-diuretic condition ANF did not affect renal tubular handling of sodium. The enhanced tubular reabsorption of sodium post-frusemide, and the failure of ANF to suppress this, could be due to activation of the RAAS and SNS.

Atrial natriuretic factor inhibits ACTH stimulated aldosterone, but not cortisol, secretion in man

The effects of human ANF 99-126 on the aldosterone and cortisol responses to ACTH infusion were studied in 8 normal volunteers. ACTH infusion caused a significant rise in aldosterone and cortisol on each study day. On the day that ANF was concomitantly infused the aldosterone, but not the cortisol, response to ACTH was significantly attenuated. These results show that a pharmacological dose of ANF selectively inhibits ACTH mediated mineralocorticoid as opposed to glucocorticoid release in man. These results support in vitro and in vivo findings from animal experiments. These findings also compliment previous studies showing that ANF inhibits ANG II stimulated aldosterone release in normal subjects.

Consequences of fluid loss in patients treated with ACE inhibitors

Three patients are described in whom haemodynamic collapse and acute renal failure occurred following intercurrent gastrointestinal fluid loss during treatment with an angiotensin converting-enzyme inhibitor. The possible consequences of blockade of the formation of angiotensin II during fluid loss are discussed.

Association between liberalization of Scotland's liquor licensing laws and admissions for self poisoning in West Fife

Data were collected prospectively on 2868 consecutive patients admitted for self poisoning between 1971 and 1982. Analysis showed a dramatic increase in the frequency of alcohol taken in association with self poisoning, in both sexes, after the liberalization of Scotland's liquor licensing laws. This increase, however, did not appear to affect the severity of overdoses or the outcome. Total admission rates for self poisoning increased with relaxation of the liquor licensing laws, and since overdoses associated with alcohol tend to occur at night these impose considerable strain on casualty departments and acute admitting units.

Changes in erythrocyte transketolase activity and the thiamine pyrophosphate effect during storage of blood

Whole blood and washed erythrocytes from nutritionally normal and abnormal elderly patients were stored at room temperature, 4 degrees C and -20 degrees C for up to 14 days. In both groups, and under all storage conditions, the erythrocyte transketolase (ETK) activity and the thiamine pyrophosphate (TPP) effect decreased with time of storage. The ETK activity for specimens stored at -20 degrees C decreased significantly by day 14 (P less than 0.05). The TPP effect in specimens stored at -20 degrees C decreased significantly in the nutritionally abnormal group at 4 days (P less than 0.05) and in the nutritionally normal group by day 14 (P less than 0.05). These significant changes in ETK activity and TPP effect with storage can lead to misleading interpretation of thiamine nutritional status.