Effect of captopril on heavy proteinuria in azotemic diabetics

Can progression of renal disease be prevented?

Renal disease from a variety of causes often progresses to end-stage renal failure. The progression may be caused by factors accompanying, but not initiating, renal injury. These factors include glomerular hyperfiltration, glomerular hypertension, systemic hypertension, and hyperlipidemia. Studies, primarily in animals, indicate that causative factors may be altered by control of systemic hypertension, dietary protein restriction, administration of angiotensin-converting enzyme inhibitors or calcium channel blockers, and plasma lipid control. Whether such interventions will significantly alter progressive renal disease in humans is, as yet, uncertain.

Choosing initial therapy for hypertension. A personal view

With numerous safe and effective antihypertensive drugs now available, the clinician should no longer choose only diuretic agents or beta-adrenergic receptor blockers (beta-blockers) as initial therapy. Five classes of agents, including angiotensin converting enzyme inhibitors, beta-blockers, calcium entry blockers, peripheral alpha 1-adrenergic receptor blockers, and thiazide diuretic agents, are all appropriate monotherapy in properly selected patients. The choice depends on efficacy, side effects, demography, comorbidity, dosage schedule, cost, mechanism of drug action, and the pathophysiology of the patient's hypertension. Extensive data are now available that will assist the clinician in choosing an agent that has the greatest probability of success without the need for extensive biochemical or hemodynamic evaluation.

Hypertension in the person with diabetes

Hypertension is more common in persons with both insulin-dependent and noninsulin-dependent diabetes. Pathophysiologic mechanisms that result in an increased prevalence of essential hypertension in noninsulin-dependent diabetes, premature diastolic hypertension in insulin-dependent diabetes, and systolic hypertension in both forms of diabetes are described. Aggressive treatment of the hypertension associated with diabetic nephropathy will result in a deceleration of renal decompensation. The commonly used antihypertensives that successfully treat hypertension in the non-diabetic population often have unacceptable side effects in the diabetic population. Rational approaches to the treatment of diabetic hypertension in general and in circumstances unique to the hypertensive diabetic individual are described.

A comparison of the hypotensive effects of captopril and atenolol in the treatment of hypertension in diabetic patients

In a double-blind, randomized, cross-over study in 23 diabetic patients, insulin treated (N = 11) or noninsulin treated (N = 12), with mild to moderate hypertension, the hypotensive effects of captopril and atenolol were compared. Five patients had overt diabetic nephropathy. All patients received 50 mg twice daily of either drug. Treatment periods lasted 6 weeks and were preceded and separated by a placebo period. Two patients dropped out, one because of intermittent claudication during atenolol, one with cardiac arrhythmia during placebo. Blood pressure was reduced from 165 +/- 5/96 +/- 1 to 154 +/- 5/89 +/- 2 mmHg (mean +/- SEM: P less than 0.01) during captopril and from 171 +/- 5/98 +/- 1 to 159 +/- 6/89 +/- 2 mmHg (P less than 0.01) during atenolol. These antihypertensive effects are not significantly different. There was a wide inter- and intraindividual variation in hypotensive response to both drugs, which may have important consequences for treatment strategies. No consistent differences between insulin and noninsulin treated patients were seen. Parameters of glycemic control did not change during any therapy, neither in insulin treated nor in non-insulin treated patients. Albuminuria and renal function did not change. During captopril treatment one patient complained of a non-productive cough. Two patients experienced a severe hypoglycemic reaction during atenolol. No other major side-effects were seen. In conclusion, this study showed equal hypotensive effectivity of 100 mg captopril and 100 mg atenolol daily in hypertensive diabetics, without evident effect on glycemic control.

Hypertension

An estimated 58 million Americans are at increased risk of morbidity and premature death due to high blood pressure (BP) and require some type of therapy or systematic monitoring. This article focuses on recent advances in our understanding of the pathogenesis of hypertension, new approaches to the diagnosis and treatment of secondary hypertension, and current views of the most appropriate nonpharmacologic and pharmacologic therapy for essential hypertension. In view of the extremely high prevalence of the disorder, emphasis is placed on efficient and cost-effective strategies for diagnosing and managing the hypertensive patient. Recent evidence indicates that nonpharmacologic therapy, including dietary potassium and calcium supplements, reduction of salt intake, weight loss for the obese patient, regular exercise, a diet high in fiber and low in cholesterol and saturated fats, smoking cessation, and moderation of alcohol consumption produces significant sustained reductions in BP while reducing overall cardiovascular risk. Accordingly, nonpharmacologic antihypertensive therapy should be included in the treatment of all hypertensive patients. In persons with mild hypertension, nonpharmacologic approaches may adequately reduce BP, thereby avoiding the expense and potential side effects of drug therapy. In patients with more severe hypertension, nonpharmacologic therapy, used in conjunction with pharmacologic therapy, can reduce the dosage of antihypertensive medications necessary for BP control. Patients treated with nonpharmacologic therapy only should be followed closely, and if BP control is not satisfactory, drug therapy should be added. The large number of drugs available for use in hypertension treatment, coupled with our rapidly expanding knowledge of the pathophysiology of hypertension and of the adverse effects of these drugs in individual patient groups, make it possible to individualize antihypertensive treatment. When used as monotherapy, most agents effectively lower BP in the majority of patients with mild or moderate essential hypertension. Thus, a single agent from one of four classes: diuretics, angiotensin-converting enzyme inhibitors, calcium channel blockers, and beta-adrenergic blockers, usually provides effective BP control with minimal side effects in most patients. Therapy should be initiated with the agent most likely to be effective in BP lowering and best tolerated. If the initial agent is ineffective at maximal recommended therapeutic doses or has undue side effects, an alternative agent from another class should be tried. When monotherapy is unsuccessful, a second agent, usually of a different mechanism of action, should be

Short term effect of captopril on microalbuminuria induced by exercise in normotensive diabetics

OBJECTIVE

To investigate whether captopril has any effect on microalbuminuria induced by exercise in normotensive diabetic patients with early stage nephropathy.

DESIGN

Randomised, double blind, crossover trial.

SETTING

Outpatient department.

PATIENTS

22 diabetics with stage II nephropathy (urinary albumin excretion rate less than 20 micrograms/min; 15 with type I diabetes and seven with type II), 32 patients with stage III nephropathy (urinary albumin excretion rate 20-200 micrograms/min; 14 with type I diabetes and 18 with type II), and 10 normal subjects.

INTERVENTIONS

Four exercise tests on a cycle ergometer: the first two under basal conditions and the third and fourth after subjects had received captopril (two 25 mg doses in 24 hours) or placebo (two tablets in 24 hours).

END POINT

Exercised until 90% of maximum heart rate achieved.

MEASUREMENTS AND MAIN RESULTS

Mean urinary excretion one hour after the first two exercise tests was 21 micrograms/min in normal subjects, 101 micrograms/min in diabetic patients with stage II nephropathy, and 333 micrograms/min in those with stage III nephropathy. Similar results were obtained after placebo. After captopril the urinary excretion rate one hour after exercise was significantly decreased in diabetics with stage II (36 micrograms/min) and stage III (107 micrograms/min) disease compared with placebo but not in normal subjects. Systolic and diastolic pressures were similar in the three groups after placebo and captopril had been given.

CONCLUSIONS

Captopril significantly reduces microalbuminuria induced by exercise in normotensive diabetics without affecting systemic blood pressure. Captopril may reduce renal intracapillary pressure.

Converting enzyme inhibition in chronic renal failure

Ten patients with chronic renal failure whose hypertension was controlled with triple drug therapy consisting of propranolol-hydralazine-furosemide were switched to the angiotensin-converting enzyme (ACE) inhibitor captopril for a period of 12 months. Control of hypertension was similar with both antihypertensive regimens. Clearance of inulin and of paraaminohippuric acid increased during the first 3 months of captopril therapy and remained stable thereafter. Moreover, the decline in the reciprocal of serum creatinine over time observed during triple drug therapy was arrested during therapy with the ACE inhibitor. If the salutary effects of captopril are sustained, the results obtained in the current studies would suggest that control of hypertension by ACE inhibition may be effective in slowing progression of renal failure. Future studies to answer this important question are necessary.

High-risk patients treated with enalapril maleate: safety considerations

The safety of 738 high-risk patients treated with enalapril under various clinical programs was evaluated. High risk was defined as the presence of a collagen vascular disease; a renal disease, including renovascular hypertension; or either hypertension or refractory cardiac failure with serum creatinine greater than or equal to 1.7 mg/dl at baseline. Essential hypertension was the primary diagnosis in most of these patients. Treatment with enalapril in these patients usually continued without interruption for the length of the particular protocol. The incidence of adverse reactions resulting in discontinuation of treatment was comparable to that observed with other standard antihypertensive therapies in patients with milder forms of disease. No enalapril-related neutropenia, proteinuria, dysgeusia or ageusia were reported in these high-risk patients. The incidence of discontinuation due to rash was less than 0.5%. Resolution and/or improvement of captopril-related adverse effects was observed in many patients crossed over to treatment with enalapril. In patients with collagen vascular diseases and those with severe impairment of renal function (serum creatinine greater than or equal to 3.0 mg/dl), the incidence of discontinuation due to adverse experiences or death as well as the profile of reported adverse experiences was similar to those for the total group of high-risk patients. The data suggest that enalapril is efficacious and well tolerated by the high-risk patients.

Albumin metabolism in the nephrotic syndrome: the effect of dietary protein intake

The nephrotic syndrome is characterized by increased urinary excretion of albumin and other serum proteins, accompanied by hypoproteinemia and edema formation. Nephrotic patients have lower serum albumin concentrations than do patients undergoing continuous ambulatory peritoneal dialysis when albumin and protein losses are the same in both groups, suggesting that nephrotic patients may not maximally adapt to loss of protein. The fractional rate of albumin catabolism is increased in nephrotic patients, possibly as a result of increased albumin catabolism by the kidney, but the absolute albumin catabolic rate is decreased in nephrotic patients. The rate of albumin synthesis may be increased, but not sufficiently to maintain normal serum albumin concentration or albumin pools. Augmentation of dietary protein in nephrotic rats directly stimulates albumin synthesis by increasing albumin mRNA content in the liver, but also causes an increase in glomerular permeability to macromolecules so that much if not all of the excess albumin synthesized is lost in the urine. When dietary protein is restricted, the rate of albumin synthesis is not increased either in nephrotic patients or in rats, despite severe hypoalbuminemia. Although dietary protein supplementation may lead to positive nitrogen balance, dietary protein supplementation alone does not cause an increase in serum albumin concentration or body albumin pools, and may instead cause further albumin pool depletion because of changes induced in glomerular permselectivity. The use of angiotensin-converting enzyme inhibitors may blunt the increased albuminuria caused by dietary protein supplementation and allow albumin stores to be increased.

Angiotensin converting enzyme inhibitors. II. Clinical use

Since their introduction in clinical practice in 1980, ACE inhibitors have been found useful in the treatment of hypertension and CHF. In hypertension, they are effective as monotherapy in 40% to 50% of the patients, and in combination with diuretics or calcium antagonists, they are effective in up to 85% of the patients. They are well tolerated, are not associated with depression, impotence, bronchospasm or metabolic derangements such as hypokalemia, hyperuricemia or hyperglycemia, and do not have adverse effects on the quality of life. As a result, they are preferred in hypertensive patients with CHF, left ventricular dysfunction, mental depression, older age, coronary artery disease, metabolic disorders, chronic destructive pulmonary disease, and peripheral vascular disease. In CHF they cause long-lasting hemodynamic and symptomatic improvement, improve exercise tolerance, and may lower mortality in certain patient subsets. Evolving new indications for ACE inhibitors include the diagnosis of renovascular hypertension, the prediction of surgical success, the treatment of scleroderma renal crisis, the reduction of proteinuria, renal protection, cardioprotection, the improvement of arterial compliance, in Bartter's syndrome and idiopathic edema, etc. ACE inhibitors are usually well tolerated but in some instances they may cause class-specific side effects such as hypotension; usually reversible azotemia or renal failure, especially in patients with renal artery stenosis or with CHF with low blood pressure; cough; angioedema; and hyperkalemia. Differences among ACE inhibitors are emerging and include chemical class (e.g., zinc ligand), biotransformation, potency, pharmacokinetics, prodrugs, tissue effects, additional pharmacologic properties, and drug interactions.

Treating hypertension in black compared with white non-insulin dependent diabetics: a double blind trial of verapamil and metoprolol

STUDY OBJECTIVE

To compare responses of blood pressure to the calcium antagonist verapamil and the beta blocker metoprolol in black compared with white diabetics with hypertension and to monitor urinary albumin excretion in relation to fall in blood pressure.

DESIGN

Double blind, placebo controlled, random order crossover trial with four week placebo run in period and two six week active phases separated by a two week placebo washout period.

SETTING

Outpatient department of a general hospital in a multiethnic health department. Patients--Diabetic patients with hypertension. Four dropped out before randomisation; 25 black and 14 white patients completed the trial.

INTERVENTIONS

Patients given slow release verapamil 120 mg or 240 mg twice daily with placebo or metoprolol 50 mg or 100 mg twice daily with placebo. Treatment for diabetes (diet alone or with oral hypoglycaemic drugs) remained unchanged.

END POINT

Comparison of changes in blood pressure in the two groups taking both drugs.

MEASUREMENTS AND MAIN RESULTS

Metoprolol had little effect on blood pressure in black patients (mean fall 4.0 mm Hg systolic (95% confidence interval -2.5 to 10.4 mm Hg), 4.3 mm Hg diastolic (-0.8 to 9.5)) but more effect in white patients (mean falls 13.4 mm Hg (0.1 to 26.7) and 10.6 mm Hg (4.5 to 16.7) respectively). Verapamil was more effective in both groups, with mean falls of 8.8 mm Hg (2.4 to 15.0) and 8.1 mm Hg (5.0 to 11.2) in black patients and 19.1 mm Hg (5.4 to 32.9) and 11.4 mm Hg (0.9 to 22.0) in white patients. Heart fate fell significantly in black patients taking metoprolol, which suggested compliance with treatment. Metabolic variables were unaltered by either treatment. Plasma renin activity was low in both groups after metoprolol treatment, but change in blood pressure could not be predicted from baseline plasma renin activity. Urinary albumin:creatinine ratio was independently related to baseline blood pressure but not significantly changed by treatment.

CONCLUSIONS

beta Blockers alone are not effective in treating hypertension in black diabetics. Verapamil is effective but less so than in white patients. As yet no ideal monotherapy exists for hypertension in black patients.

Hypertension and diabetes

Diabetes mellitus and hypertension are both common diseases, especially with an increasingly aged population. Hypertension accelerates the development of diabetic retinopathy, nephropathy, and peripheral vascular disease in the diabetic patient. Diabetes represents a type of premature aging and hypertension in the diabetic patient is characterized by many of the same pathophysiologic properties seen in the elderly hypertensive patient.

Prevention of diabetic nephropathy with enalapril in normotensive diabetics with microalbuminuria

STUDY OBJECTIVE

To assess the effectiveness of inhibition of angiotensin converting enzyme in preventing diabetic nephropathy.

DESIGN

Randomised follow up study of normotensive diabetics with persistent microalbuminuria (30-300 mg/24 hours) treated with enalapril or its matched placebo for one year. Double blind for first six months, single blind for last six months.

SETTING

Diabetic clinic in tertiary referral centre.

PATIENTS

Treatment group and placebo group each comprised 10 normotensive diabetics with persistent microalbuminuria.

INTERVENTIONS

Treatment group was given enalapril 20 mg daily and controls matched placebo. Patients were given antihypertensive treatment after one year.

END POINT

Albumin excretion, arterial pressure, and renal function.

MAIN RESULTS

In last three months of trial three of 10 patients taking placebo had diabetic nephropathy (albumin excretion greater than 300 mg/24 hours). No patients taking enalapril developed nephropathy and five showed normal albumin excretion (less than 30 mg/24 hours) (p = 0.005, Mann-Whitney test). Mean arterial pressure was reduced by enalapril throughout study (p less than 0.005) but increased linearly with placebo (p less than 0.05). Albumin excretion decreased linearly with enalapril but not placebo. An increase in albumin excretion with placebo was positively related to the increase in mean arterial pressure (r = 0.709, p less than 0.05, Spearman's rank test). With enalapril total renal resistances and fractional albumin clearances improved progressively (time effect, p = 0.0001).

CONCLUSION

Inhibition of angiotensin converting enzyme prevents development of nephropathy in normotensive diabetics with persistent microalbuminuria. This may be due to reduction in intraglomerular pressure and to prevention of increased systemic blood pressure. Future studies should compare long term effects of inhibitors of converting enzyme with other antihypertensive drugs.

Rational drug treatment of the hypertensive diabetic with nephropathy

Development of hypertension in Type I diabetics parallels evolution of nephropathy. In Type II diabetics, excessive prevalence of hypertension prior to the appearance of proteinuria suggests that factors other than nephropathy are operative in its pathogenesis. On the other hand, the risk of nephropathy in Type II diabetics is higher than previously appreciated. Recent evidence suggests that angiotensin II plays an important role in the induction and progression of diabetic nephropathy. This provides a rationale for antihypertensive therapy with converting enzyme inhibitors in nephropathic diabetics in whom they have been shown to lower blood pressure and diminish proteinuria. Furthermore, in a retrospective study of patients with various renal diseases (including diabetic nephropathy), the authors found suggestive evidence that converting enzyme inhibitors may also attenuate progression of renal failure to a greater extent than other antihypertensive drugs.

Some lessons from the studies of renal biopsies in patients with insulin-dependent diabetes mellitus

The authors have studied relationships of renal structure and function in more than 100 patients with insulin-dependent diabetes mellitus (IDDM), aged 13-55 years (mean, 30 years) with diabetes for 1-30 years (mean, 19 years). The authors confirmed the unique nature of the diabetic lesions that, in constellation, occur in no other disease. It was found that increased fractional mesangial volume (Vv Mes) is strongly associated with decreased glomerular filtration rate (GFR), proteinuria, and hypertension and that all patients with overt diabetic nephropathy have Vv Mes in excess of 0.35 micron 3/micron 3. This relationship results from constriction of the capillary lumen and filtration surface as a consequence of increased Vv Mes. Global glomerulosclerosis (scarring) is common in IDDM patients and appears related to arteriolar hyalinosis. Focal segmental glomerulosclerosis is a rare lesion in these patients. Having a single kidney (transplanted IDDM patients) is not associated with accelerated lesion development. The presence or absence of microalbuminuria (MA), per se, does not predict underlying glomerular structure, which may vary from the normal range to a level of pathology bordering on that regularly associated with overt nephropathy. However, when MA is associated with hypertension, or reduced GFR or both, urine albumin excretion (UAE) generally exceeds 40 mg/24 hr, and glomerular pathology is always present. The authors concluded that diabetic nephropathy is a unique renal disorder that cannot be caused by hemodynamic factors alone. The authors further conclude that MA becomes a predictor only when other features of overt nephropathy are already present and that serious diabetic glomerular lesions can be present in patients with normal UAE.

[The renin-angiotensin system in diabetic patients]

We review available data on the activity of the renin-angiotensin system (RAS), responsiveness to angiotensin II (ANG II), ANG II receptor number, and effects of inhibition of the RAS by angiotensin I converting enzyme (ACE) inhibitors in patients with diabetes mellitus. Most authors, including ourselves, observed a normal or enhanced activity of the RAS in metabolically stable diabetics. Increased but also reduced activity of the RAS was described in nephropathic diabetes. This is in contrast to the common suggestion that the RAS of diabetics is generally suppressed and functionally inactive. The last assumption was mainly based on the finding of reduced ANG II receptor numbers in anorectic, severely hyperglycemic rats. These findings could not be reproduced in man, and a higher ANG II receptor concentration on platelets of diabetics goes in parallel with the frequent finding of an enhanced pressor response to infused ANG II in diabetes. This increased responsiveness is most probably of functional importance since the RAS is not suppressed - as one would expect - in the face of a supranormal body sodium content. A number of data also indicate that renal resistance vessels display increased responsiveness to ANG II in diabetics. This may be a reason for hyperfiltration. This notion is further supported by the reduction of albuminuria which is usually observed following inhibition of the RAS with ACE inhibitors, and which may be an index of reduction of glomerular capillary pressure in human diabetes.

Acute and long-term renal effects of angiotensin converting enzyme inhibition in normotensive, normoalbuminuric insulin-dependent diabetic patients

Glomerular filtration rate (GFR) (thalamate clearance), renal plasma flow (RPF) (hippuran clearance), and urinary albumin excretion rate (AER) were measured in 10 normoalbuminuric, normotensive insulin-dependent diabetic patients and 8 normal subjects before and during acute angiotensin converting enzyme (ACE) inhibition by means of enalapril (10 mg IV). The effect of placebo versus enalapril (30 mg day-1) was also studied for 3-month treatment periods in the insulin-dependent diabetic patients. Acute ACE-inhibition caused a decline in filtration fraction (FF) from 0.259 +/- 0.011 (+/- SE) to 0.237 +/- 0.013 (2p less than 0.01) in the diabetic patients, and from 0.210 +/- 0.010 to 0.188 +/- 0.006 (2p less than 0.02) in the normal subjects. Mean arterial blood pressure was lowered from 90 +/- 1 to 84 +/- 2 mmHg (2p less than 0.01) and from 91 +/- 1 to 86 +/- 2 mmHg (2p less than 0.05). No significant change in blood glucose, AER or fractional albumin excretion (theta Alb) was seen in either group. After 3 months of enalapril treatment FF was decreased from 0.253 +/- 0.011 to 0.235 +/- 0.011 (2p less than 0.05), AER from 5.6 x/ divided by 1.7 to 4.3 x/divided by 1.6 micrograms min-1 (2p less than 0.01) and theta Alb from 1.22 +/- 0.22 x 10(-6) to 0.92 +/- 0.12 x 10(-6) (2p less than 0.02). The decline in total renal resistance was not significant (0.175 +/- 0.013 to 0.165 +/- 0.012 mmHg ml-1 min-1) and significant changes in GFR, RPF, mean arterial pressure or HbA1c were not observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Captopril in patients with type II diabetes and renal insufficiency: systemic and renal hemodynamic alterations

PURPOSE

To our knowledge, clinical studies on the long-term use of angiotensin converting enzyme inhibitors in patients with type II diabetes mellitus and nephropathy with incipient renal failure are nonexistent. We therefore assessed the effects of long-term treatment with captopril on systemic and renal hemodynamics and urinary protein excretion in patients with type II diabetes mellitus and the clinical syndrome of diabetic nephropathy.

PATIENTS AND METHODS

Twelve patients, 10 men and two women, with an average age of 52 years (range, 40 to 66), participated in the study. After the basal hemodynamic evaluation, the patients received captopril in two daily doses. The dosage was adjusted at weekly intervals in order to obtain normalization of blood pressure without exceeding the maximum allowable dosage. Four patients also received furosemide (20 to 40 mg/day).

RESULTS

After six months of treatment, the intra-arterial blood pressure fell (from 162 +/- 17/103 +/- 5 to 139 +/- 26/89 +/- 10 mm Hg) due to the reduction in total peripheral vascular resistance index (from 3,720 +/- 658 to 3,190 +/- 762 dynes/second/cm-5/m2), with no change in cardiac index (2.78 +/- 0.36 to 2.79 +/- 0.47 liters/minute/m2). No significant change was seen in renal vascular resistance (from 30,175 +/- 5,371 to 30,173 +/- 5,372 dynes/second/cm-5/1.73 m2) and in filtration fraction (from 26 +/- 8 to 27 +/- 10 percent). A slight, not significant, decrease in renal plasma flow (from 243 +/- 97 to 217 +/- 108 ml/minute/1.73 m2), in glomerular filtration rate (from 57 +/- 17 to 51 +/- 19 ml/minute/1.73 m2), and in proteinuria (from 4.50 +/- 3.10 to 3.40 +/- 2.31 g/day) was also observed.

CONCLUSION

Our findings suggest that captopril is an effective antihypertensive agent in patients with diabetic nephropathy, but the renal beneficial effects seem to be limited when this syndrome is complicated by renal insufficiency.

The hypertensive patient with concomitant cardiovascular disease

Many drugs for the treatment of hypertension are available in the United States today. Of the various factors that determine the appropriate treatment for a particular patient, the presence of concomitant heart disease requires specific tailoring of the antihypertensive therapy. Coronary artery disease, aortic insufficiency, congestive heart failure, left ventricular hypertrophy, premature ventricular contractions, supraventricular arrhythmias, mitral valve prolapse, orthostatic hypotension, and aortic dissection are some of the conditions that influence the choice of treatment. Diabetes places hypertensive patients at increased risk of heart disease, and exercise and sexual function are other considerations that govern the selection of treatment for the hypertensive person. For all of these conditions, more than one drug choice is often possible, but usually hypertensive patients can be treated with a beta-blocker or a calcium channel blocker in these special circumstances.

The progression of renal disease

The diversity of its causes, the unpredictability of its clinical course, and our expanding knowledge of the conditions that may exacerbate or retard its progression suggest that glomerular sclerosis cannot be attributed to a single aberration in glomerular physiology. Nonetheless, the welter of clinical and experimental observations is beginning to yield a pattern. Agents or conditions injurious to glomerular epithelium tend to cause glomerular sclerosis. Agents or conditions that induce short-term or long-term activation of mesangial cells may lead to glomerular sclerosis. Indeed, one contribution of the healthy epithelium may be to serve as a tonic inhibitor of the intraglomerular processes arising from mesangial-cell activation. Long-term activation of the mesangium is associated with the proliferation and infiltration of cells and with the expansion of the mesangial matrix--the antecedents of sclerosis. We anticipate that different diseases associated with glomerular sclerosis will be found to depend to varying extents on these two potential mechanisms of sclerosis. Beyond a certain threshold of glomerular injury, glomerular diseases share an additional factor: the capacity of both intrinsic cells and infiltrating cells to alter the microenvironment of the glomerulus so that sclerosis progresses inexorably long after the disappearance of the initiating insult. Several potential risk factors may contribute to the progression of chronic renal disease. These factors include systemic hypertension, proteinuria, hyperlipidemia, high protein intake, and probably conditions that lead to glomerular hypertrophy. Interventions designed to minimize the potential contribution of these factors to the progression of renal insufficiency may halt or slow the loss of function of the kidney. Clinical trials designed to examine the effects of these factors on the progressive course of renal insufficiency will help to establish their role and relative importance in humans.

Lisinopril pharmacokinetics in chronic renal failure

1. Lisinopril, a new orally active angiotensin converting enzyme inhibitor, was given to eight patients with stable chronic renal failure, in a dose of 5 mg 24 h-1 for 1 week. Creatinine clearance of the subjects ranged from 0.22 to 1.11 ml s-1. Lisinopril pharmacokinetics were studied over 8 days. 2. There was a close correlation between creatinine clearance and total 'area under the curve' over the 8 days of study (r = -0.88, P less than 0.05), and plateau lisinopril concentration and creatinine clearance (r = -0.77, P less than 0.05). 3. Serum angiotensin converting enzyme activity was inhibited in proportion to log serum lisinopril concentration (r = -0.99, P less than 0.001). Calculated IC50 was 47 ng lisinopril ml-1. from pooled data, with individual patients IC50 ranging from 20 to 70 ng lisinopril ml-1. 4. Creatinine clearance was unaltered by treatment. Serum potassium rose to over 5 mmol 1-1 in four patients, without adverse clinical effect.

Phosphate restriction reduces proteinuria of the uninephrectomized, diabetic rat

Proteinuria is the clinical hallmark of diabetic nephropathy and the harbinger of progressive renal disease. Therefore, the present study was designed to examine the effect of phosphate restriction on the proteinuria of streptozotocin-induced diabetes mellitus in the rat. Uninephrectomy was performed in experimental and control groups to worsen the degree of diabetic nephropathy. Proteinuria was prevented in Sprague-Dawley rats treated with the intestinal phosphate binder, dihydroxyaluminum aminoacetate (DHAAA) (24.75 +/- 20.35 mg/d at 3 months v control, 77.45 +/- 44.72 mg/d, P less than 0.001); an effect that was independent of protein and caloric intake, plasma albumin and lipids, severity of diabetes, mean arterial pressures, cardiac output, and renal calcium accumulation. The effect of DHAAA on protein excretion and glomerular hemodynamics was examined in similarly prepared Munich-Wistar rats; these rats did not tolerate long-term studies. Three weeks of DHAAA again caused a consistent fall in proteinuria (5.98 +/- 7.28 v 34.94 +/- 24.28 mg/d) and in transmembrane hydraulic pressure difference (41.1 +/- 1.2 v 46.4 +/- 2.8 mm Hg, P less than 0.005). In conclusion, phosphate restriction significantly decreases the proteinuria of Sprague-Dawley and Munich-Wistar uninephrectomized rats with streptozotocin-induced diabetes mellitus. Micropuncture of Munich-Wistar rats suggests that a reduction of intraglomerular pressure may be at least partially responsible for such an effect.

Safety issues during antihypertensive treatment with angiotensin converting enzyme inhibitors

When captopril was first introduced, it was used in high doses for severe hypertension, often in the presence of renal insufficiency, and side effects such as proteinuria, rash, neutropenia, and altered taste sensation were noted. Upon analysis, these effects were most commonly seen in patients with renal disease, autoimmune disease, or collagen vascular disease. These complications usually reversed rapidly upon discontinuation of treatment. In contrast, the growing use of the angiotensin converting enzyme inhibitors, captopril and enalapril, for treating mild to moderate hypertension and the trend toward the use of lower doses has shown these agents to be well tolerated with a low frequency of troublesome adverse effects. In fact, the original spectrum of adverse effects has virtually disappeared with the use of lower doses in patients with uncomplicated hypertension. In low doses, the converting enzyme inhibitors produce remarkably few incidences of symptomatic discomfort; the most common is skin rash, which often responds to dosage reduction. Cough and rare occurrences of angioedema have also been reported. Moreover, evidence is evolving that indicates that the converting enzyme inhibitors may sometimes decrease proteinuria and improve renal function; these effects may be especially important in diabetic hypertensive patients. Of note, these drugs can also attenuate the unwanted metabolic side effects of concurrent diuretic treatment.

Hemodynamic factors in the pathogenesis of diabetic nephropathy

The pathogenesis of the diabetic glomerular lesion is unknown. However, cumulative indirect evidence favors hemodynamic factors associated with the abnormal endocrine environment as the cause of diabetic angiopathy. Experimental evidence suggests that the increased hydrostatic pressures in capillary beds, a hallmark of the early stages of insulin-dependent diabetes, are associated with macromolecular leakage leading to the typical thickening of glomerular capillary basement membrane and increased glomerular mesangial matrix even prior to the occurrence of systemic hypertension. Patients with renal or carotid artery stenosis seem to be protected against diabetic nephropathy and retinopathy on the stenosed side. The first signal of diabetic nephropathy even before deterioration of the renal function is microalbuminuria detected by sensitive methods such as radioimmunoassay. Not only in hypertensive, but even in normotensive diabetic patients with microalbuminuria antihypertensive therapy has been shown to reduce albumin excretion rate and to slow the progression of diabetic nephropathy. Once overt diabetic nephropathy has been established, hypertension is a constant accompaniment of the disease. Thus, hypertension may be a cause as well as a result of diabetic nephropathy. Tight control of blood sugar in close association with antihypertensive treatment reducing blood pressure to a lower normal limit, possibly with agents that specifically decrease glomerular capillary hydraulic pressure are the corner stone in protection against progression of the diabetic angiopathy.

Cardiovascular risk factors and antihypertensive therapy

Reduction of elevated blood pressure is effective in reducing morbidity and mortality from cardiovascular disease in general. Striking decreases in stroke, congestive heart failure, and renal impairment have been observed when blood pressure is reduced. However, the ability of traditional, diuretic-first, stepped-care therapeutic algorithms to reduce the occurrence of myocardial infarction or angina has been exceedingly difficult to demonstrate. An increased frequency of sudden death among hypertensive men with electrocardiographic abnormalities has been observed in some diuretic-based treatment trials. The failure of conventional therapy to reduce coronary artery disease and death has forced a re-appraisal of antihypertensive treatment. The risk factors for coronary disease are reviewed in detail with an emphasis on the impact of various classes of antihypertensive drugs on these factors. The emergence of effective antihypertensive agents that lower blood pressure without adversely affecting cardiovascular risk factors provides a new opportunity to further extend the benefit of treatment by reducing such risk.

Renal perfusion and function. The implications of converting enzyme inhibition

Because the kidney is both the source of circulating renin and the final determinant of the state of sodium balance, which in turn defines responsiveness to angiotensin II, one might have anticipated substantial interest in the impact of converting enzyme inhibitors on the kidney when these agents were developed. The lessons learned about the role of the renin-angiotensin system in normal renal perfusion and function, and possible disorders of control that contribute to disease in patients with essential hypertension, renovascular hypertension, and chronic progressive renal parenchymal disease are reviewed. In each case, the lessons here have important implications for the clinical application of converting enzyme inhibition.

Efferent glomerular arteriolar constriction: a possible intrarenal hemodynamic defect in hypertension

A variety of mechanisms involving the kidney subserve the control of arterial pressure and the development and maintenance of hypertension. The precise and direct delineation of intrarenal hemodynamic mechanisms has been possible only by micropuncture techniques. Since these methods can be used only in the anesthetized animal, intrarenal hemodynamic assessment in conscious intact experimental animals or patients with essential hypertension must be indirect. Using indirect methods, calculated pressures in our laboratory have demonstrated differences in intrarenal hemodynamics between SHR and normotensive WKY rats, notably enhanced responsiveness of the efferent arteriole to alpha adrenergic agonist stimulation. When the calcium antagonist diltiazem was administered to the SHR or to patients with essential hypertension, it effected an increased renal blood flow and a well-maintained glomerular filtration rate without hyperfiltration. These indirect data suggest that there may be an efferent arteriolar abnormality in genetically mediated hypertension that may be reversed with certain calcium antagonists.

Cyclosporine A induced remission of relapsing nephrotic syndrome in children

We treated 20, steroid resistant or steroid dependent and cyclophosphamide or chlorambucil treated, relapsing nephrotic patients with oral cyclosporine A for eight weeks. Cyclosporine A was started at 7 mg/kg/day and titrated to maintain HPLC level of 100 to 200 ng/ml. Of 20 patients, 14 had a complete remission and the remaining 6 had a reduction in their proteinuria. The mean serum albumin of the 14 responders rose from 2.1 g/dl to 4.1 g/dl (P less than 0.00001) after cyclosporine A therapy. The mean serum cholesterol of the 14 responders decreased from 394 mg/dl to 184 mg/dl (P less than 0.0001) after cyclosporine A therapy. The mean creatinine clearance of the 20 patients (104 ml/min/1.73 m2) was unchanged (107 ml/min/1.73 m2) after eight weeks of cyclosporine A. By life table analysis, 40% of the responders show a sustained remission of up to a year. Cyclosporine A responders had a higher T3 cell count prior to therapy compared to nonresponders (69 +/- 5.54% vs. 61 +/- 6.4%, P less than 0.02). Pre-therapy interleukin-2 levels measured in 10 patients were normal or supranormal in 8, 6 of whom were treatment responders. Two patients with low interleukin-2 levels were nonresponders. Cyclosporine A can be used to induce a remission in relapsing nephrotic patients, and short-term cyclosporine A therapy does not produce nephrotoxicity.

Pathogenesis of diabetic glomerulopathy: hemodynamic considerations

Early stages of diabetes mellitus are characterized by glomerular hyperfiltration in humans and experimental animals. In diabetic rats, single nephron hyperfiltration results from elevations in the glomerular capillary plasma flow rate and hydraulic pressure, which are in turn associated with progressive albuminuria and morphologic injury. Interventions that ameliorate these hemodynamic adaptations afford protection against structural injury. Dietary protein restriction, which lowers glomerular filtration, perfusion, and hydraulic pressure, retards glomerular injury and limits capillary basement membrane thickening in both the glomerular and retinal circulatory beds. Alternatively, selective control of glomerular capillary hypertension using angiotensin I converting enzyme inhibitor therapy limits glomerular injury in this model as well. Each of these interventions is effective even in the absence of improved metabolic control, implying that hemodynamic factors per se are important in this pathogenic process. The pathophysiologic mechanisms of diabetic hyperfiltration remain incompletely elucidated. Recent studies invoke a potential role for atrial natriuretic peptide (ANP). Strict metabolic control abolishes the elevations of glomerular filtration rate and of plasma ANP levels in moderately hyperglycemic diabetic rats. Moreover, infusion of a specific ANP antibody reverses hyperfiltration in diabetic rats. Thus, hyperglycemia-induced chronic volume expansion may trigger ANP release, which in turn contributes to diabetic hyperfiltration. Hemodynamic factors may play an important role in the pathogenesis of extrarenal microangiopathy as well. Elevated peripheral capillary blood flows and/or hydraulic pressure may be found in many peripheral capillaries, in association with thickening of the capillary basement membrane. Dietary protein restriction, which lowers blood flow to many organs, limits retinal as well as glomerular basement membrane thickening in diabetic rats, suggesting that hemodynamically mediated structural injury is a diffuse phenomenon in the diabetic state.

Platelet-inhibitor treatment of diabetic nephropathy: a 10-year prospective study

We prospectively evaluated a platelet-inhibitor regimen of dipyridamole and aspirin in 28 patients with insulin-dependent diabetes mellitus and well-established nephropathy. After a mean treatment period of 4.3 years, iothalamate clearance (Ciot) was reasonably well maintained and urinary protein excretion was reduced in 7 patients (25%), whereas 21 (75%) had progressive nephropathy. Analysis of outcome revealed that all 7 patients with stable nephropathy and 9 of the 21 with progressive disease had baseline Ciot values that exceeded 50 ml/min per 1.73 m2. Shortened platelet survival improved after 3 months of treatment, and the distribution between patients who had stable and those who had progressive disease was approximately equal. Mean changes in fasting plasma glucose level, glycosylated hemoglobin, and blood pressure did not differ between these two groups. In a short-term protocol, urinary protein and thromboxane B2 significantly declined, whereas variable urinary levels of prostaglandin E2, 6-ketoprostaglandin F1 alpha, and Ciot did not change after 3 months of treatment with dipyridamole and aspirin. These findings suggest that treatment with dipyridamole and aspirin may stabilize renal function by reducing platelet hypersensitivity and production of thromboxanes by platelet or renal tissue (or both). In turn, constrictor activity in the glomerular vessels, mesangial contractility, and glomerular membrane permeability are decreased. These data also add evidence in support of a role for thromboxane A2 in the pathogenesis of experimental and human glomerular disease.

The development and progression of chronic renal disease. Can it be prevented or attenuated?

Many forces contribute to the immutable progressive deterioration of renal diseases. This review focuses on the pernicious haemodynamic response of the kidney to an initial loss of mass. Afferent arteriolar dilatation, coupled with relative or absolute efferent arteriolar constriction, causes the hydrostatic pressure in the intervening glomerular capillaries to increase. While sustaining the glomerular filtration rate, the glomerular hypertension may ultimately scar and destroy the kidney. Experimental studies in animals persuasively argue that the high glomerular capillary pressures do indeed contribute to progressive renal damage. Whether this observation is translatable into human renal diseases is the subject of ongoing clinical investigation. The role of dietary protein restriction and converting enzyme inhibitors in reducing this glomerular hypertension and in potentially attenuating the progression of a wide range of renal diseases is also discussed.

Aspects of the role of intraglomerular pressure as a cause of progressive renal damage

Renal damage in hypertension was thought to be a result of excessive renal arteriolar constriction leading to ischaemia and nephron damage. However, more recent studies have shown that in animal models the aetiology is one of increased intraglomerular pressure, and there is strong evidence that this is also the case in patients with essential hypertension. The problem is therefore one of inadequate constriction of afferent arterioles allowing increased systemic pressure to be transmitted to the glomerular capillaries. Since angiotensin II preferentially constricts the efferent arterioles, and since hypertensive patients have increased renovascular sensitivity to angiotensin II, this may explain why angiotensin-converting enzyme inhibitors are the only drugs which actually lower intraglomerular pressure and why they reduce renal damage in hypertensive disease.

Development and progression of chronic renal disease: can it be prevented or attenuated?

Following its initiation, renal disease tends to progress relentlessly to end stage, necessitating dialysis or transplantation or causing death. Studies have shown that metabolic, hematologic and hemodynamic adaptations by the damaged kidney underlie the progressive nature of the disease. This review underscores the hemodynamic maladaptations and consequences and the evidence that suggests that glomerular hypertension is a necessary accompaniment to renal damage. The evidence reviewed indicates that high pressure develops in fragile glomerular capillaries after loss of a critical amount of renal mass and causes progressive sclerosis and destruction of remaining nephrons. This maladaptive renal response ensures progressive destruction in a variety of renal diseases including diabetes mellitus. Reduced protein intake and converting enzyme inhibitor therapy may prevent or attenuate the progression of these diseases.

Systemic hypertension, diabetes mellitus and the kidney

Diabetic nephropathy is manifested by albuminuria, hypertension and progressive loss of renal function. Only one-third of patients with insulin-dependent diabetes mellitus of juvenile onset develop nephropathy and the risk of nephropathy does not increase with increasing duration of diabetes. Hypertension occurs almost exclusively in patients with nephropathy. Therefore, there is a subset of patients at risk for both nephropathy and hypertension. It is important to identify the patients destined to develop nephropathy, to define the pathophysiology responsible for the nephropathy in this subset of patients and to develop programs to interrupt the pathophysiology early in its course and hopefully prevent the progression to end-stage renal failure. Potential markers to identify patients who will develop nephropathy include a family history of hypertension, increased glomerular filtration rate and renal mass and presence of significant microalbuminuria. Studies are needed to evaluate various classes of drugs for their efficacy in altering the pathophysiologic hemodynamic changes leading to nephropathy.

Reversal of target-organ involvement in systemic hypertension: a pharmacologic experience

Systemic hypertension is a disease manifested by a persistently elevated arterial pressure produced by an increased total peripheral resistance, which is more or less uniformly distributed throughout the component circulations. Unless pressure is reduced and maintained at controlled levels, it will be associated with impaired function of the primary target organs of the disease: brain, heart, kidneys and blood vessels. The effects of an elevated arterial pressure on heart and kidneys and the effects of antihypertensive therapy on target-organ involvement will be discussed. Cardiac involvement primarily relates to left ventricular hypertrophy and its regression with treatment, and in the kidney to altered intrarenal hemodynamics and effects of treatment. The role of calcium antagonists, primarily diltiazem, is discussed with reference to its hemodynamic effects on reducing total peripheral resistance and arterial pressure associated with regression of ventricular hypertrophy and maintenance of renal blood flow without inordinately increasing glomerular hydrostatic pressure. Studies suggest a beneficial role of diltiazem in the treatment of essential hypertension.