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1 The effects of labetalol, bethanidine and combined treatment with both drugs were compared in a within-patient randomized cross-over study in mild essential hypertension. Attention was directed to whether or not labetalol and bethanidine differed in their pattern of effect on arterial BP and whether evidence of synergism was apparent. 2 At the doses used labetalol significantly lowered systolic and diastolic BPs and heart rate lying, sitting, standing and after exercise. The dose of bethanidine used did not affect heart rate significantly while lowering systolic and diastolic BPs only after exercise and less clearly on standing. Combined treatment lowered BPs on standing and after exercise and heart rate after exercise. 3 The type and frequency of side-effects were similar with bethanidine and labetalol but were much less with combined treatment. 4 No evidence of synergism was observed.

Athough in general, measurement of renal vein renin appears to give a good prediction as to the subsequent response to surgery, its main value lies in its ability to reflect changes in renal plasma flow; true changes in renin secretion rate being much more difficult to detect. Although it is a little early to say how much information can be derived from saralasin infusions, caution must be exercised in necessarily assuming that the test accurately reflects subsequent surgical response.

A desulphurised tailings cover was installed to reduce oxygen diffusion into underlying sulphidic tailings at the Detour Lake Mine in Ontario, Canada between 1998 and 1999. This paper reviews the outcomes of the original characterisation of the desulphurised cover in 2000 and evaluates performance of the cover following an investigation completed 11 years after installation. A holistic view of the tailings system is discussed including water quality testing, fish populations within the tailings management area, and geochemical analyses of the desulphurised cover. An initial site investigation and numerical modelling were completed by Sjoberg-Dobchuk et al. (2003) to instrument the cover and monitor the water content profile, as well as to collect tailings samples for geotechnical and geochemical characterisation. Numerical simulations concluded that the tailings cover would not maintain greater than 85% saturation within the region of the beach. However, oxygen flux rates through the desulphurised cover to the underlying tailings were still found to be reduced to 2 mole/m2/yr or less due the consumption oxygen by the residual sulphide content within the cover profile. This study indicated the cover was effective in preventing ARD. A follow-up study was conducted in August 2011 to assess the performance of the cover system prior to flooding by new tailings. A site investigation was conducted at the original instrumentation locations to collect samples for geochemical analyses. The laboratory results and visual observations indicated the cover is performing well, without maintaining >85% saturation. Water quality sampling of the tailings pond water generally met or exceeded the Ontario Provincial Water Quality Objectives and the tailings pond supported a substantial population of four fish species. The study provided further confirmation that the profile of the desulphurised tailings cover profile has not become acidic and the cover performance has met the initial design expectations.

Recently there has been extensive development of orally active angiotensin converting enzyme (ACE) inhibitors in addition to those already marketed, for example, captopril, enalapril, lisinopril and ramipril. It was initially thought that ACE inhibitors were likely to be most useful as antihypertensive agents in conditions in which circulating renin and angiotensin II were elevated. However, it is now clear that they can also lower arterial pressure when plasma renin is not high. In addition, they have beneficial effects in cardiac failure. Thus, captopril, enalapril, lisinopril and ramipril can be used in the treatment of mild to moderate hypertension either alone or in conjunction with diuretics or calcium antagonists. Broadly speaking, efficacy appears to be similar to that of beta-blockers or diuretics. Unfortunately, however, there are no long term studies comparing one ACE inhibitor with another or with other classes of antihypertensive agents. Furthermore, there are no prognostic studies which show that use of ACE inhibitors reduces morbidity or mortality in hypertension. Many new ACE inhibitors are undergoing clinical assessment, including alacepril, cilazapril, fosenopril, perindopril, quinapril and ramipril. The drugs vary, in that some exist in the active form whereas others are prodrugs which are converted to the active agent following absorption. In addition they each possess one of several ligands, for example, carboxyl, phosphinyl or sulfhydryl groups, and so vary in their affinity for ACE. Although many of these agents are renally excreted, a small number are metabolised via the liver (e.g. quinapril and spirapril) and this may prove advantageous in the presence of renal impairment. In common with captopril and enalapril, the new ACE inhibitors inhibit the renin-angiotensin system and initial results suggest that they are effective in lowering blood pressure in essential hypertension. Furthermore, they reduce systemic vascular resistance in the absence of a reflex tachycardia. There are a number of adverse effects which are attributable to the pharmacological mechanism of the ACE inhibitors as a group; these include hypotension, particularly in patients with high renin levels, prior diuretic use, renal impairment or in the elderly. Additional adverse effects may relate to chemical structure. The high incidence of adverse effects noted in early studies related to excess dosage and to the presence of a sulfhydryl group, which the more recently developed ACE inhibitors lack. The adverse effects most commonly reported with established and new ACE inhibitors include headache and fatigue, cough, skin rashes, hypotension and diarrhoea. As a group, ACE inhibitors have an acceptable but not negligible adverse effect burden.(ABSTRACT TRUNCATED AT 400 WORDS)

The extent of the contribution of serotonin (5-hydroxytryptamine; 5 HT) to cardiovascular physiology and vascular disease has, despite absorbing interest, remained elusive and enigmatic since the discovery of the amine. It has been said that when Nature has available a competent substance, she will employ it where she will [1]. This concept is epitomized by the variety of roles serotonin has been called upon to perform, well illustrated by the range and diversity of topics that have been addressed in the present symposium. Such versatility requires that, in order to achieve a given physiologic effect while avoiding toxicity, an appropriate concentration of the hormone is delivered to the site of action. If this needs the hormone to be transported across a system where its action is unwanted, active concentrations must be avoided in that zone. One stratagem by which this appears to be effected in the case of serotonin is by ensuring that virtually all of the amine in the peripheral circulation is platelet bound and therefore inactive. Even when a gross excess of serotonin circulates, as, for example, in the carcinoid syndrome, little or none is free in

Nebivolol was compared in a dose of 5 mg once daily with enalapril 10 mg once daily over 7 months in a double-blind randomised trial in essential hypertension. The two drugs had very similar sustained effects in lowering both systolic and diastolic pressures; neither had an orthostatic component. Both drugs were well-tolerated. No haematological, biochemical, or urinary abnormalities were seen.

The efficacy and acceptability of 5 mg nebivolol once daily, a long-acting, vasodilating cardioselective beta blocker that additionally facilitates the L-arginine/nitric oxide system, was assessed in a double-blind, randomized trial in comparison with 20 mg nifedipine retard twice daily in patients with essential hypertension. At 2 weeks of treatment, nebivolol was significantly more effective. Thereafter, both drugs effectively and similarly lowered systolic and diastolic pressures without orthostatic effect. Nebivolol had a trough-to-peak antihypertensive effect ratio of 90%. Nifedipine gave the expected side effects of headache, flushing, and edema. Nebivolol was well tolerated. Nebivolol slightly but significantly lowered heart rate. Neither drug adversely affected plasma levels of lipids.

Several studies have shown that treatment of hypertension does not return risk to normal. Reasons include imperfect clinic organization, poor patient compliance, adverse drug effects, inadequate blood pressure control, and, particularly, failure to affect the atheromatous complications of hypertension. Future therapeutic efforts, and especially drug design, should be directed to these needs

A double-blind, randomised, parallel-group trial was conducted in patients with essential hypertension in British general practices, of nebivolol 5 mg, atenolol 50 mg, and placebo each given once daily. Both active drugs, in comparison with placebo, caused highly significant and similar reductions in systolic and diastolic pressures without orthostatic effect, and small significant falls in heart rate. Both active drugs were well tolerated, nebivolol marginally more so. Nebivolol, a long-acting, cardioselective, vasodilating beta-blocker which acts partly via the l-arginine/nitric oxide mechanism, appears potentially valuable for the treatment of hypertension.

The efficacy and acceptability of nebivolol 5 mg and enalapril 10 mg, each given once daily, were compared in essential hypertension in a multicentre, randomised, double-blind trial over 3 months. For the index pre-declared variable, sitting diastolic pressure at trough drug level, nebivolol achieved greater falls in pressure (-12.3 vs -9.9 mmHg; P = 0.009) and a higher response rate (70% vs 55%; P = 0.002). The trough-to-peak sitting diastolic ratios also favoured nebivolol (84% vs 60%, P = 0.002). Nebivolol, but not enalapril, slightly but significantly lowered heart rate. Both drugs were well-tolerated, although enalapril was accompanied by a significantly higher incidence of coughing.

A wide range of drug classes, frequently including centrally acting agents, has been used in clinical trials in hypertension which have shown benefit. Although therapy has clearly limited the complications of hypertension, further improvement is needed, especially concerning coronary artery disease.Future interest therefore centres on drugs that do not worsen diabetes mellitus, do not cause dyslipidaemia, or induce potassium loss, while not provoking drowsiness, depression, other troublesome side-effects, or being associated with rebound hypertension when stopped. The centrally acting imidazoline agonists merit detailed study in this regard.

A double-blind placebo-controlled dose-response trial of nebivolol, a cardioselective beta-blocking drug which also induces endothelium-dependent dilatation via nitric oxide, has been performed. Nebivolol reduced blood pressure (BP) in a dose dependent way, and was shown to be effective given once daily, without appreciable differences between peak and trough drug levels. There was no postural component to the BP fall. There was no clear inferiority of efficacy in black patients. A single daily dose of 5 mg was appropriate, with no evident advantage at 10 mg. The drug was well tolerated, even at 10 mg daily. BP control was achieved largely in the absence of typical side effects of beta-blockade. The combination of properties of nebivolol renders it an attractive addition to the antihypertensive repertoire.

Beta-adrenoceptor blocking agents are established as one of the principal classes of antihypertensive agents. Despite progressive refinements over the years, they still possess some unwanted effects, which limit their considerable value. In recent years a wide range of variations upon the beta-blocker theme has been developed. The full clinical advantages of the newer agents remain to be defined.

Present evidence in man is clear and consistent in showing a minor or negligible role of α-1 antagonism in the antihypertensive action of ketanserin. An interaction between marked 5HT-2 and weak α-1 antagonism is by contrast a distinct possibility. The clinical role, if any, of ketanserin in depleting monoamine pools requires to be examined.

The therapy of hypertension has evolved over the past 50 years from the short-term care of a small number of hospitalized patients with severely elevated blood pressure and organ damage to a major community health problem involving a substantial proportion of the population with mild to moderate hypertension. In the beginning, severe side effects and toxicity of antihypertensive agents were accepted by patients and doctors as the price that had to be paid for this lifesaving therapy. The results of recent therapeutic trials show the benefits of antihypertensive treatment for mild to moderate hypertension. This has changed the attitudes towards treatment. The aim of modern antihypertensive therapy is the reduction of the risk of cardiovascular disease. The management of hypertensive patients therefore has to include the minimization of other controllable risk factors such as diabetes, hypercholesterolemia, alcohol, and cigarette smoking. Blood pressure lowering can be achieved not only by pharmacological substances but also by non-drug methods, e. g., reduction of sodium intake, reduction of body weight, reduction of alcohol intake, increased physical activity, and meditation. These methods are part of an antihypertensive strategy with different priorities in the European countries.

The carcinoid syndrome can arise when effluent blood from carcinoid tumor tissue gains access to the systemic, as opposed to the portal, venous system. Features include facial flushing, diarrhea, wheezing, right-sided cardiac lesions, and retroperitoneal fibrosis. Attacks of flushing, diarrhea, and wheezing can be provoked by bolus injections of adrenaline, noradrenaline, or pentagastrin. While serotonin usually predominates, carcinoid tumors can also secrete, in varying proportions, 5-hydroxytryptophan, kallikrein, kinins, substance P and other neuropeptides, prostaglandins, catecholamines, and histamine. Of these, serotonin, kinins, histamine, and substance P are possible mediators of flushes; serotonin and substance P of hyperperistalsis; and serotonin, kinins, or histamine of bronchial constriction. Despite the gross excess of circulating serotonin, nearly all is platelet bound and therefore inactive. Very little is free in plasma. Demonstration of a contribution of serotonin to carcinoid attacks requires assay of free plasma serotonin; measurements of whole blood or serum serotonin are of little value. Some, but not all, provoked flushes have been shown to be accompanied by a rise in free plasma serotonin or substance P; an increase in circulating kinins has been more consistently shown. The 5HT2 antagonist ketanserin has been found to inhibit both provoked and spontaneous attacks of flushing, diarrhea, and dyspnea in a proportion of patients with carcinoid syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Serotonin (5-hydroxytryptamine; 5-HT) is widely distributed in the body and subserves many functions. Tissue specificity of action is aided by differential receptor structure and function; the type 2 (5-HT2) receptor mediates arterial constriction and platelet aggregation. Very little serotonin is free in plasma, most being platelet-bound; however, local platelet activation and consequent serotonin release can present free serotonin to peripheral tissues. Serotonin, acting via the 5-HT2 receptor, can contribute to a range of cardiovascular problems, including portal hypertension, Raynaud's phenomenon, carcinoid flushes, preeclampsia, hypertension, arterial atheroma, and restenosis after angioplasty or thrombolysis. 5-HT2 antagonists have a potential therapeutic role in all these conditions. The diversity of such syndromes requires that the term "vascular protection" should not be applied loosely, but must always be precisely defined. Future 5-HT2 antagonists will probably be of two kinds: (a) with weak accompanying alpha 1 antagonism where blood pressure reduction is needed; and (b) as "pure" 5-HT2 antagonists, for use where arterial pressure falls are best avoided.

The ability of large doses of exogenous angiotensin II to cause widespread multifocal microscopic myocardial necrosis in the rabbit has been confirmed. Angiotensin II also consistently produced acute renal failure with, less consistently, renal tubular necrosis. Norepinephrine infusions caused histologically indistinguishable myocardial lesions, but did not detectably affect renal function or histology. Severe renal failure, induced by bilateral nephrectomy (with or without concurrent glycerol administration) was not associated with similar cardiac lesions. Acute renal failure of comparable or greater severity to that induced by angiotensin II was produced by intramuscular cephaloridine, and was not associated with cardiac lesions. Rabbits infused with saline intravenously or “sham”-operated by simply opening and closing the peritoneal cavity did not develop renal failure and showed no cardiac or renal lesions histologically. Myocardial lesions, apparently identical to those seen in the rabbits, were observed postmortem in three patients known to have had high circulating levels of angiotensin II before death, although in all three cases alternative explanations are possible. Unexplained arrhythmia, cardiac arrest, and central chest pain without clear cardiographic or serum enzyme evidence of myocardial infarction occurred in two other subjects with very high plasma levels of angiotensin II. These attacks ceased after bilateral nephrectomy and a consequent fall in plasma angiotensin II. The cardiac attacks in these five patients all occurred during or shortly after procedures, such as sodium-depleting dialysis, renal artery surgery, or diazoxide administration, known to cause increases in plasma concentrations of renin and angiotensin II.

We measured arterial plasma angiotensin II concentration, renal blood flow, and arterial blood pressure in six conscious dogs during intravenous infusion of angiotensin II (5, 10, and 20 ng/kg per min). The same measurements were made on a different occasion in the same six animals, while they were conscious, before and during constriction of a main renal artery. Arterial blood pressure and plasma angiotensin II rose and renal blood flow decreased in both experiments. The similarity of regressions for plasma angiotensin II concentration and arterial blood pressure in the two experiments strongly suggests that the rise of circulating angiotensin II after renal artery constriction is sufficient to account for the hypertension by its direct pressor action. As discussed, a different mechanism seems likely to be involved in the later stages of renal hypertension. Angiotensin II is more likely to be in the 5-isoleucine form than in the 5-valine form in the dog. In contrast to the rat, plasma concentrations of the heptapeptide (angiotensin III), hexapeptide, and pentapeptide fragments of angiotensin II are low in the dog.

Hydralazine was dissolved in 0.5% drinking saline (40 mg/1000 ml) labelled with isotope 22Na and given to spontaneously hypertensive rats for four weeks. Another group of rats were given isotope labelled saline only and served as control. Measurements of total exchangeable sodium, blood pressure, pulse rate and weight were performed before and repeatedly during treatment. Before treatment exchangeable sodium, blood pressure, pulse rate, and weight were no different between the groups. The antihypertensive effect of hydralazine was marked and maintained throughout the experiment. No significant changes were found in pulse rate. Both groups gained weight similarly. Exchangeable sodium increased at the same rate in both groups along with the weight increase. Thus, chronic hydralazine treatment effectively reduces blood pressure in spontaneously hypertensive rats without causing measurable sodium or fluid retention.

Infusion of angiotensin II into a patient with dexamethasone-suppressible hyperaldosteronism caused a brisk increase in plasma aldosterone concentration. In this behaviour, the patient resembled those patients with idiopathic hyperaldosteronism rather than those with tumorous primary hyperaldosteronism. Sodium depletion of a small group of patients with mild essential hypertension elicited a spectrum of increases in plasma aldosterone levels ranging from zero to normal. Angiotensin II infusion in both sodium replete and deplete states also caused variable aldosterone responses. These results suggest that the derangement of adrenal function in this condition varies continuously in severity.

Malignant phase hypertension can occur in women taking combined oestrogen-progestagen oral contraceptives and is almost certainly caused by the medication. In previous reports the preparations used contained 50–100 μg oestrogen. We describe four cases, two of which we believe to be the first recorded examples of the malignant phase induced by preparations containing only 30μg of oestrogen. In one case, brain damage due to over-rapid reduction of very high blood pressure is described. Malignant phase hypertension may occur within weeks of commencing therapy, or after several years. Although recent preparations contain lower doses of oestrogen, there is no room for complacency when prescribing oral contraceptives. Close medical supervision and regular blood pressure measurements during such treatment are mandatory.

The effects of standard oral glucose loading (100 g) on plasma aldosterone and some regulatory factors were assessed in patients with primary hyperaldosteronism and normal subjects. Following overnight fast, mean plasma glucose was identical (10 patients and normal subjects approximately matched per age and sex); plasma insulin, potassium and renin levels were lower and plasma aldosterone higher in the patients. Glucose loading significantly increased plasma glucose and insulin concentrations and decreased plasma potassium and aldosterone levels in both groups; plasma renin activity was significantly increased only in normal subjects. The increases in plasma insulin and the decreases in plasma potassium or aldosterone tended to be blunted in primary hyperaldosteronism. Relationships among glucose-induced changes in plasma aldosterone and other factors were assessed by multiple regression analysis in these patients and normal subjects as well as an additional group of 21 normal subjects; in the latter, plasma cortisol was also measured and found to decrease significantly after glucose loading. Changes in plasma aldosterone correlated (P less than 0.025) more closely with those in plasma potassium in the patients and with variations in plasma renin activity in the normal subjects. These findings suggest that complex metabolic changes occur following glucose ingestion which are capable of modifying aldosterone secretion in normal subjects and primary hyperaldosteronism. The aldosterone-inhibitory effect of glucose tends to be blunted in the latter disorder. This could be related at least in part to an impaired insulin response in primary hyperaldosteronism.

1. To explore the effects of exercise on plasma atrial natriuretic peptide (ANP) concentrations, eight normotensive volunteers performed maximal treadmill exercise in sodium replete and deplete states. 2. Baseline immunoreactive plasma ANP concentrations were significantly lower during sodium depletion. During exercise plasma ANP rose in all subjects on both occasions. Plasma peptide responses were attenuated by sodium depletion with peak exercise levels only double baseline values, in contrast to the threefold increase in ANP concentrations observed when subjects were sodium replete. 3. Plasma renin and aldosterone concentrations also rose with exercise. In contrast to changes in plasma ANP, the responses of both were enhanced by sodium depletion.

1. Arterial pressure, plasma electrolytes and exchangeable sodium were measured in 91 patients with essential hypertension and in 121 normal control subjects. Total body sodium, exchangeable potassium and total body potassium were also measured in some of the hypertensive patients. 2. Mean plasma sodium concentration was slightly but significantly lower in the hypertensive patients as a group, but mean values for other electrolyte measurements were close to normal or predicted normal. 3. Exchangeable sodium was not related to arterial pressure in normal subjects but in hypertensive patients exchangeable sodium correlated significantly with systolic and diastolic pressures. These correlations were significant with two methods of expressing exchangeable sodium, in the whole group of patients, in men and in older patients. Exchangeable sodium was not significantly related to arterial pressure in young patients. 4. Total body sodium also correlated significantly with systolic and diastolic pressures in hypertensive patients. 5. Exchangeable sodium was significantly related to age in hypertensive patients but not in normal subjects. Mean exchangeable sodium was significantly lower than normal in young patients. 6. Plasma potassium concentration was not related to arterial pressure in normal subjects but in essential hypertensive patients plasma potassium concentration, exchangeable potassium and total body potassium correlated negatively with systolic and diastolic pressures. These correlations were also significant in young, but not in old patients.

Presynaptic receptors have recently been identified on nerves supplying vascular smooth muscle. Renin is stored in juxtaglomerular cells in the wall of the afferent glomerular arteriole and the JG cell is probably derived from vascular smooth muscle. Nervous stimuli exert an important influence on release of renin, but the nature of the receptors involved is not agreed. We propose that there are presynaptic receptors associated with the JG apparatus as with vascular muscle and that a mechanism of this sort gives a better account of data on renin release.

Not all patients with renovascular hypertension and a demonstrated stenotic lesion are benefited by surgery; in addition to the customary radiologic and biochemical studies, measurement of renal ve...

1 Upright tilting in normal volunteers caused increases in plasma active and total renin, angiotensin II and aldosterone; a slight but significant fall in inactive renin accompanied these changes. 2 The alterations in the renin-angiotensin-aldosterone system on tilting took up to 1 h upright to become fully established. 3 Large intravenous doses of propranolol or metoprolol attenuated, without abolishing, the rises in active renin, angiotensin II, and aldosterone; the attenuation was most evident soon after tilting and was largely overcome by 1 h upright. Inactive renin did not fall significantly after beta-adrenoceptor blockade. 4 Intravenous frusemide caused immediate rises in plasma active, total and inactive renin, angiotensin II, and aldosterone, which then declined over 2 h despite increasing cumulative sodium losses. 5 Intravenous propranolol or metoprolol attenuated, without abolishing, these early increases in the components of the renin-angiotensin-aldosterone system after frusemide. 6 Prior oral metoprolol or propranolol, while significantly slowing the heart, did not limit the early rise in plasma angiotensin II following intravenous frusemide. 7 Thus in contrast to previous workers, we did not find that propranolol eliminated the response of the renin-angiotensin system to upright tilting; in part this difference appeared to be due to the longer tilt we employed. 8 Also in contrast to earlier work, we found attenuation by both intravenous propranolol and metoprolol of the immediate rise in renin after intravenous frusemide.

The renin-angiotensin system has a range of physiological actions concerned with the control of the circulation. Angiotensin II has both an immediate and a delayed pressor effect, it stimulates the secretion of aldosterone and antidiuretic hormone, promotes thirst, stimulates the sympathetic nervous system at various sites while inhibiting vagal tone, and has a range of direct effects on the kidney. Several aspects of this range of actions can become deranged in a number of forms of hypertension as well as in congestive cardiac failure. Hence much effort has been directed in recent years to the development of agents designed to interfere with the renin-angiotensin system and to apply these clinically in the treatment of hypertension and congestive cardiac failure. Orally active converting enzyme inhibitors are of proven benefit not only in renovascular hypertension, but also, when combined with loop diuretics, in the treatment of intractable hypertension as well as, both alone and in combination with thiazide diuretics, in the treatment of essential hypertension. In congestive cardiac failure controlled trials have shown that converting enzyme inhibitors can improve exercise tolerance while diminishing lassitude, correct potassium deficiency and limit ventricular arrhythmias. Energetic efforts are being made to develop orally active inhibitors of the enzyme renin itself, since these would be more specific in action than the presently available and very successful converting enzyme inhibitors.

1. The effects of polyethylene glycol (PEG) 200 administered by gavage on electrolyte and water excretion were investigated in the rat. 2. PEG 200 led, in intact rats, to dose-related increased drinking and to diuresis. 3. In the first 2 h after PEG 200 administration, water consumption in intact rats exceeded urine output. 4. PEG 200 enhanced the excretion of both sodium and potassium, but the sodium excretion was proportionately greater, resulting in an elevation of the urinary sodium/potassium ratio. 5. Bilateral nephrectomy was not accompanied by increased drinking in PEG 200-treated rats, although raised serum osmolality was seen. 6. Thus, given by gavage, PEG 200 is not an inert vehicle for drug administration.

The converting-enzyme inhibitor, captopril, in a dose of 450 mg daily, was given together with a diuretic to eleven patients with severe hypertension unresponsive to previous therapy. Sustained control of blood pressure was achieved. Plasma angiotensin II and aldosterone fell significantly, whereas plasma active and total renin, and blood-angiotensin-I concentrations increased. Adverse effects included temporary taste disturbance, tachycardia, nephrotic syndrome, and possible drug-induced Guillain-Barreneuropathy. The combination of captopril and diuretic is thus very effective in controlling refractory hypertension. However, because of the frequency and severity of side- effects it should probably be used only in patients whose blood pressure has previously been uncontrolled by other means.

Amiloride (75 mg daily) and spironolactone (300 mg daily) were given to five normal subjects for 7 days in order to compare metabolic effects at maximal doses. Blood pressure, body weight, Na+ and K+ balance, and plasma concentrations of Na+, K+, active and total renin, angiotensin II, aldosterone, 11-deoxycorticosterone (DOC), 18-hydroxydeoxycorticosterone (18-OH DOC), corticosterone (B), 18-hydroxycorticosterone (18-OH B) and cortisol were measured before and on each day of treatment. Natriuresis and K+ retention were significantly greater with amiloride. Plasma K+ increased from 4.1 +/- 0.2 to 4.9 +/- 0.2 mmol/l (mean +/- s.d.) on amiloride and from 4.0 +/- 0.2 to 4.4 +/- 0.2 mmol/l with spironolactone. Stimulation of renin, angiotensin II, aldosterone and 18-OH B occurred with both drugs but was greater with amiloride in each case. A transient decrease in systolic and diastolic blood pressure was observed after 2 days of spironolactone treatment but not with amiloride. The slope of the regression of aldosterone on angiotensin II during spironolactone treatment was less than that with amiloride, consistent with partial blockade of aldosterone synthesis by spironolactone. These data suggest that the maximum metabolic effects of amiloride exceed those of spironolactone.

The response of plasma aldosterone to fludrocortisone administration (400 mug 12-hourly for 3 days) was studied in twenty-two patients with primary hyperaldosteronism. No difference was observed in the response between those patients with an adrenal adenoma and those with bilateral adrenocortical hyperplasia, there being no significant change in plasma aldosterone levels across the test period. No separation between the groups was seen when basal plasma renin concentration was related to the aldosterone level following fludrocortisone. It is concluded that the test is of little value in the pre-operative differentiation of these conditions. Twenty-three patients with no demonstrable cause for their hypertension and four with elevated levels of plasma deoxycorticosterone were similarly studied for comparison. These groups demonstrated a normal fall in plasma aldosterone levels following fludrocortisone.