Effect of captopril on heavy proteinuria in azotemic diabetics

Comparative effects of antihypertensives on proteinuria: angiotensin-converting enzyme inhibitor versus alpha 1-antagonist

Control of hypertension improves the course of renal disease. We compared the renal hemodynamic and permselective responses to an angiotensin-converting enzyme inhibitor (CEI) (enalapril) and an alpha 1-antagonist (prazosin) in 14 patients with established glomerular disease. A single-blinded, randomized, cross-over design was used consisting of a 3-week baseline period followed by two 4-week treatment periods, which were separated by a 4-week washout period. During the treatment periods, the CEI or alpha 1-antagonist was added to the patients' baseline antihypertensive medications. Mean arterial pressure (MAP) was reduced to similar levels by both drugs, although the time-averaged blood pressure throughout the study was higher with the alpha 1-antagonist. Twenty-four-hour urinary protein, albumin, and IgG excretion were not significantly different at the end of the CEI and alpha 1-antagonist periods. However, compared with baseline values, significant decreases in total protein and IgG excretion occurred only during the CEI period, while albumin excretion decreased with both drugs. A 22% decrease in the fractional clearance of albumin (4.95 +/- 1.44 to 3.88 +/- 1.57 x 10(-3); P less than 0.01) and a 49% decrease in the fractional clearance of IgG (1.58 +/- 0.42 to 0.81 +/- 0.28 x 10(-3); P less than 0.001) occurred during CEI therapy with no significant changes in these parameters being seen with alpha 1-antagonist therapy (albumin: 4.95 +/- 1.44 to 4.48 +/- 1.51 x 10(-3), P = NS; IgG: 1.58 +/- 0.42 to 1.71 +/- 0.70 x 10(-3), P = NS). At the time of the fractional clearance measurements, MAP proved to be lower on the CEI. Reanalysis of the data for the subgroup of 11 patients without differences in MAP during the clearance period demonstrated a beneficial effect favoring CEI. Except for the greatest decreases in blood pressure (21 to 30 mm Hg), a greater antiproteinuric effect for a given decrease in blood pressure was seen with the CEI. Additionally, reduction in proteinuria occurred in a subset of seven patients whose baseline MAP was in the normotensive range. In conclusion, lowering MAP improves proteinuria. CEI appears to exert a more favourable effect even at similar MAP. Reductions in blood pressure, even within the accepted normal range, lessen permselective defects.

Angiotensin converting enzyme inhibitors for reduction of proteinuria in children with steroid-resistant nephrotic syndrome

The effects of angiotensin converting enzyme inhibitors (ACEI) on proteinuria, renal function, and serum proteins were evaluated in six children with steroid-resistant nephrotic syndrome and proteinuria of 3-15 g/24 h (277 +/- 47 mg/m2 per hour). Following ACEI, proteinuria decreased from 7,408 +/- 2,385 (mean +/- SEM) to 3,746 +/- 1,395 mg/24 h (P less than 0.05). Creatinine clearance was 87.8 +/- 22.6 before and 96.4 +/- 23.6 ml/min per 1.73 m2 after ACEI. In two patients, inulin and para-aminohippuric acid clearances were normal before and after ACEI, together with parallel reductions of urine protein of 50% and 46%. Clearance of total protein was reduced by 56% following ACEI, compared with reduction in the clearance of gamma globulin by 58% and albumin by 39.5%. No significant change was seen in blood pressure, serum albumin, or total protein following ACEI. After ACEI, diuretic doses were able to be reduced or eliminated in three patients. Reduction of proteinuria was sustained during a followup period of 11-20 months in three patients. ACEI may be of benefit in the clinical management of children with steroid-resistant nephrotic syndromes, allowing reduction in diuretic requirements.

Enalapril can treat the proteinuria of membranous glomerulonephritis without detriment to systemic or renal hemodynamics

The effect of enalapril on renal hemodynamics and glomerular permselectivity was studied in eight patients with nephrotic syndrome secondary to biopsy-proven membranous glomerulonephritis. The patients received the drug in incremental doses (median, 5 mg) until 24-hour urinary protein excretion had decreased persistently by 30%. Median treatment duration was 6 weeks. Patients were studied three times: (I) after a 4-week run-in period, (II) on the final day of treatment, and (III) after a 4-week wash-out. Median 24-hour urinary protein excretion decreased on treatment from 10.45 g/d to 5.25 g/d and increased to pretreatment levels after the drug was stopped (P less than 0.05 for both changes). Fractional clearance of dextrans greater than 4.1 nm decreased on treatment, indicating both a reduction of macromolecules passing through the shunt pathway of the glomerular basement membrane (GBM) and a possible decrease in ultrafiltration coefficient. There were no significant changes in glomerular filtration rate (GFR), effective renal plasma flow (ERPF), or mean arterial blood pressure (MAP) throughout the study. The effect of enalapril in treating proteinuria appears therefore to be due to a specific intraglomerular action.

Influence of prostaglandin E1 on heavy proteinuria in slightly azotaemic diabetics

Treatment of non-insulin-dependent diabetes mellitus patients with nephropathy of the nephrotic type using 40 micrograms prostaglandin E1 given intravenously twice daily for 4 weeks reduced the urinary protein concentration. Prostaglandin E1 also increased the total serum protein and serum albumin concentrations, and reduced creatinine clearance and plasma renin activity following frusemide loading. Treatment with the prostaglandin did not, however, significantly affect the blood urea nitrogen and the serum creatinine concentration. It is concluded that prostaglandin E1 has overt effects on diabetic nephropathy.

Nephrotic proteinuria without hypoalbuminemia: clinical characteristics and response to angiotensin-converting enzyme inhibition

Although hypoalbuminemia is a fundamental characteristic of nephrotic syndrome (NS), there are many patients with massive proteinuria that do not develop hypoalbuminemia. We have studied the clinical and biochemical characteristics of 19 patients with persistent massive proteinuria (greater than 5 g/d) and normal serum albumin (group I) in comparison with 16 patients with similar proteinuria excretion, but persistent hypoalbuminemia (group II). Most of group I patients had diagnoses suggesting glomerular hyperfiltration (focal glomerulosclerosis [FGS] associated with vesicoureteral reflux [VUR], reduction of renal mass, proteinuria associated with obesity, sclerotic phase of idiopathic crescentic glomerulonephritis [GN] in contrast with those of group II, in which membranous GN was the most frequent diagnosis. We prospectively investigated differences in the antiproteinuric effect of captopril, an antiotensin-converting enzyme inhibitor (ACEI); after 6 months of treatment, proteinuria decreased clearly in group I (7.1 +/- 1.7 to 3.7 +/- 1.7 g/d; P less than 0.001), whereas no significant changes were observed in group II (8.1 +/- 2.4 to 8.8 +/- 4 g/d). Serum creatinine (Scr) remained stable during captopril treatment in group I, whereas three patients in group II showed a worsening of renal function.(ABSTRACT TRUNCATED AT 250 WORDS)

Enalapril improves albuminuria by preventing glomerular loss of heparan sulfate in diabetic rats

Angiotensin converting enzyme (ACE) inhibitors, particularly enalapril and captopril, have been shown to decrease proteinuria in diabetic animals and human subjects. Since heparan sulfate proteoglycan confers a negative charge on the glomerular basement membrane, and either decreased synthesis or loss of this charge causes albuminuria in diabetic animals, we examined the possibility that enalapril prevents albuminuria through glomerular preservation of heparan sulfate in long-term diabetic rats. A total of 22 male Wistar rats were used in the study. Diabetes was induced in 15 rats by a single intraperitoneal injection of streptozotocin (60 mg/kg). The remaining 7 rats received buffer. One week following induction of diabetes, 8 diabetic rats were allowed to drink tap water containing enalapril at a concentration of 50 mg/liter; the remaining 7 diabetic and 7 nondiabetic rats were given only tap water. The drug treatment was continued for 20 weeks. Systolic blood pressure and 24-hr urinary excretion of albumin were measured at 2, 8, 16, and 20 weeks. At the end of 20 weeks, all rats were killed, kidneys were removed, and glomeruli were isolated by differential sieving technique. Total glycosaminoglycan and heparan sulfate synthesis was determined by incubating glomeruli in the presence of [35S]sulfate. Characterization of heparan sulfate was performed by ion-exchange chromatography. Systolic blood pressures were significantly lower in enalapril-treated diabetic rats compared to untreated diabetic rats. Diabetic glomeruli synthesized less heparan sulfate than glomeruli from nondiabetic rats. Also, glomerular heparan sulfate content of diabetics was significantly lower than that of nondiabetics. Further characterization of heparan sulfate showed that the fraction eluted with 1 M NaCl was significantly lower and the fraction eluted with 1.25 M NaCl significantly higher in diabetic than in normal rats. Enalapril treatment normalized not only glomerular synthesis and content but also various fractions of heparan sulfate in diabetic rats. Diabetic rats excreted increased quantities of heparan sulfate and albumin than nondiabetic rats. Enalapril therapy prevented both these increases in diabetic rats. These data suggest that enalapril treatment improves albuminuria through preservation of glomerular heparan sulfate and prevention of its urinary loss in diabetic rats.

Effects of captopril on diabetic nephropathy in hypertensive women

The effects of the angiotensin converting enzyme inhibitor captopril on blood pressure, proteinuria, creatinine clearance and metabolic control in diabetic nephropathy have been evaluated. Captopril 144 mg per day was given to 8 longstanding, insulin-dependent, diabetic females with nephropathy. The blood pressure was significantly reduced (systolic 45.4, diastolic pressure 30.6 and mean arterial pressure 33.8 mm Hg after 24 weeks of treatment). Plasma renin activity rose significantly from a basal value of 1.60 to 6.71 ng.ml-1.h-1, and so did serum potassium (from 4.57 to 4.83 mEq.1-1). Serum aldosterone fell from 161 to 70.9 pgm.ml-1 and from 27.3 to 15.3 micrograms.24 h-1 in plasma and urine, respectively, after 6 months on captopril therapy. Urinary protein excretion was decreased by about 48% and creatinine clearance remained unchanged throughout the study. Plasma triglycerides and cholesterol also remained unchanged, and glycosylated haemoglobin was significantly reduced from 13.8 to 10.2% after captopril. The results suggest that captopril is a useful drug to treat hypertension in patients suffering from diabetic nephropathy, as the decline in kidney function can be reduced without impairing glucose tolerance or the lipid profile.

Hypothesis: insulin is responsible for the vascular complications of diabetes

It is proposed that the systemic hyperinsulinemia and hepatic portal hypoinsulinemia that occurs with conventional injectable preparations of insulin currently used in the treatment of patients with diabetes mellitus is largely responsible for the morbidity associated with this disease. Epidemiological evidence and animal experimentation strongly support systemic hyperinsulinemia as a major factor in genesis of atherosclerosis in diabetic patients. In addition, in vitro studies demonstrate a direct effect of insulin on endothelial cell and arterial smooth muscle proliferation. On the other hand, inadequate hepatic delivery of insulin is associated with overproduction of renal vasoregulatory factors leading to glomerular hyperfiltration and ultimately to glomerulosclerosis and its clinical endpoint--end-stage renal disease. In the absence of widespread success of pancreatic and islet-cell transplantation as a means to deliver insulin physiologically into the hepatic portal circulation, methods must be devised and perfected to accomplish such delivery using approaches such as orally administering insulin in intestinal-enzyme protected capsules. Until such methods of delivery are available for safe and widespread use, one should abandon the illusory goal of rigid glucose control in favor of methods that reduce insulin requirement. Along these lines, dietary restriction and aerobic exercise should be the major life style changes advised for diabetic patients. Reduction of glomerular hyperfiltration in diabetic patients can be promoted with the use of low protein diets and/or angiotensin converting enzyme inhibitors.

Diabetic nephropathy: new directions in management

Approximately 6 million people in the United States are known to be diabetic, with an estimated 4 million individuals having undiagnosed diabetes mellitus. The metabolic derangements of both insulin-dependent diabetes mellitus (IDDM) and noninsulin-dependent diabetes mellitus (NIDDM) result in widespread end-organ damage, including progressive kidney failure. Since its initial description in 1936, the incidence of diabetic nephropathy has progressively increased, and it is now the most common cause of newly diagnosed end-stage renal disease (ESRD) requiring renal replacement therapy in the United States. While basic research efforts into pathogenesis continue, there is significant interest in clinical interventions that may slow the progression of diabetic renal disease. In addition, the options available for renal replacement therapy have increased and improved substantially in recent years.

Tissue and plasma angiotensin converting enzyme and the response to ACE inhibitor drugs

1. There is a body of circumstantial and direct evidence supporting the existence and functional importance of a tissue based RAS at a variety of sites. 2. The relation between circulatory and tissue based systems is complex. The relative importance of the two in determining haemodynamic effects is unknown. 3. Despite the wide range of ACE inhibitors already available, it remains unclear whether there are genuine differences related to tissue specificity. 4. Pathological states such as chronic cardiac failure need to be explored with regard to the contribution of tissue based ACE activities in generating acute and chronic haemodynamic responses to ACE inhibitors. 5. The role of tissue vs plasma ACE activity may be clarified by study of the relation between drug concentration and haemodynamic effect, provided that the temporal dissociation is examined and linked to circulating and tissue based changes in ACE activity, angiotensin peptides and sympathetic hormones.

Diabetic renal disease in type 1 diabetes: aetiology and prevention

Diabetic renal disease affects a subset of about 35% of patients with Type 1 diabetes and is characterized by a triad comprising increased albuminuria, arterial pressure, and volume fraction of the mesangium. This leads to a decline in the glomerular filtration rate and ultimately end-stage renal failure or premature cardiovascular mortality. Individuals at risk can be detected before the development of persistent proteinuria by screening for microalbuminuria which has proved predictive of clinical nephropathy in about 80% of cases. Microalbuminuria is often accompanied by subclinical increases in arterial blood pressure and plasma lipid levels and is usually not apparent until 5 years after stabilization of newly diagnosed diabetes. This latter finding suggests that microalbuminuria is an indicator of early disease rather than a marker of susceptibility to it. Recent evidence suggests that diabetic renal disease may be linked to a familial, possibly genetically determined, predisposition to arterial hypertension or to some factor closely related to the risk of hypertension. This underlying predisposition may be one of the mechanisms leading to severe glomerular damage and may help to explain why clinical renal disease only occurs in a subset of diabetic patients. A number of therapeutic interventions, ranging from strict blood glucose control to low-protein diet and angiotensin-converting enzyme inhibition are effective in reducing or preventing further increases in microalbuminuria. If current long-term trials confirm that treatment of microalbuminuric diabetic patients prevents the onset of heavier persistent proteinuria secondary prevention of diabetic renal failure may become possible. The current criteria for diagnosis of diabetic nephropathy will then require revision.

Prevention of albuminuria by captopril in diabetic rats

1. Streptozotocin diabetic rats were treated with captopril (50 mg l), an angiotensin converting enzyme-inhibitor, in drinking water for 20 weeks. 2. Systolic blood pressure and 24-hr urinary excretions of heparan sulfate and albumin were done at 2, 8, 16 and 20 weeks. 3. At the end of 20 weeks, all rats were killed, kidneys removed and glomeruli isolated. 4. Total glycosaminoglycan and heparan sulfate synthesis were determined by incubating glomeruli in the presence of 35S-sulfate. 5. Captopril significantly lowered blood pressure in diabetic rats 8 weeks after treatment. 6. Diabetic glomeruli synthesized less total glycosaminoglycan and heparan sulfate than glomeruli from nondiabetic rats. 7. Further characterization of heparan sulfate by ion-exchange chromatography showed that the fraction eluted with 1 M NaCl was significantly lower and the fraction eluted with 1.25 M NaCl significantly higher in diabetic than in normal rats. 8. Therapy with captopril normalized not only glomerular synthesis and content but also various fractions of heparan sulfate in diabetic rats. 9. Excretions of heparan sulfate and albumin were significantly higher in diabetic than in nondiabetic rats. 10. Captopril therapy did significantly lower but not normalize both these excretions in diabetic rats. 11. The data suggest that catopril therapy improves albuminuria through preservation of glomerular heparan sulfate and prevention of its urinary loss in diabetic rats.

Type I glycogen storage disease: kidney involvement, pathogenesis and its treatment

Type I glycogen storage disease (GSD-I) is due to the deficiency of glucose-6-phosphatase activity in the liver, kidney and intestine. Although kidney enlargement occurs in GSD-I, renal disease has not been considered a major problem until recently. In older patients (more than 20 years of age) whose GSD-I disease has been ineffectively treated, virtually all have disturbed renal function, manifested by persistent proteinuria; many also have hypertension, renal stones, altered creatinine clearance or a progressive renal insufficiency. Glomerular hyperfiltration is seen in the early stage of the renal dysfunction and can occur before proteinuria. In younger GSD-I patients, the hyperfiltration is usually the only renal abnormality found; and, in some patients, microalbuminuria develops before clinical proteinuria. The predominant underlying renal pathology is focal segmental glomerulosclerosis. Renal stones and/or nephrocalcinosis are also common findings. Amyloidosis and Fanconi-like syndrome can occur, but rarely. The risk factors for developing the glomerulosclerosis in GSD-I include hyperfiltration, hypertension, hyperlipidemia and hyperuricemia. Dietary therapy with cornstarch and/or nasogastric infusion of glucose, aimed at maintaining normoglycemia, corrects metabolic abnormalities and improves the proximal renal tubular function. Long-term trial will be needed to assess whether the dietary therapy may prevent the evolution or the progression of the renal disease.

The effect of angiotensin-converting enzyme inhibition and dietary protein restriction in the treatment of proteinuria

Both angiotensin-converting enzyme inhibitors and dietary protein restriction have been reported to reduce urinary protein losses in patients with chronic glomerular diseases. We evaluated these two therapies in 12 such patients ingesting a constant metabolic diet containing 1.6 g protein/kg body weight per day. After a steady-state was achieved during a 3-week baseline period, patients were randomly assigned to either enalapril, titrated to reduce mean arterial pressure by 10 mm Hg, or an isocaloric 0.8 g/kg protein diet. Five patients in each group completed 3 additional weeks of observation during the treatment period. Enalapril resulted in an average reduction in urinary protein and albumin losses of 26% and 33%, respectively, without reducing creatinine clearance. Albumin synthesis was unchanged and nitrogen balance increased slightly (+142.8 +/- 85.7 mmol/d [+2.0 +/- 1.2 g/d], P = 0.075). Dietary protein restriction had no consistent effect on proteinuria or albuminuria, whereas albumin synthesis (25.9 +/- 3.4 v 21.5 +/- 2.9 g/d/1.73 m2, P less than 0.05) and nitrogen balance (-135.6 +/- 92.8 mmol/d [-1.9 +/- 1.3 g/d], P = 0.10) decreased. Both therapies resulted in a modest increase in plasma potassium concentration. Whether the maintenance of albumin synthesis in the presence of a reduction in urinary protein losses will convey a long-term advantage to treatment of proteinuric patients with angiotensin-converting enzyme inhibitors remains to be determined.

Can the rate of progression of chronic renal failure be altered?

The cost of renal replacement therapy for end-stage renal disease in the United States exceeds three billion dollars per year. Nonimmunologic mechanisms may contribute to progressive renal injury in renal failure of diverse etiologies. Based on the potential adverse renal effects of these processes, a number of dietary and pharmacologic interventions have been proposed as being potentially beneficial in slowing the rate of progression of chronic renal failure to end-stage renal disease. This article reviews current evidence in animal models and humans supporting the efficacy of each of the proposed interventions.

Renal disease in noninsulin-dependent diabetes mellitus

Diabetic nephropathy now accounts for approximately one-third of all patients who develop end-stage renal disease. The estimated cost to supply renal replacement therapy for this population now exceeds $750 million. The relatively recent realization that half of these individuals suffer from noninsulin-dependent diabetes mellitus has sparked increased interest in attempts to understand the pathologic processes involved and how they may be similar or different from those alterations seen in insulin-dependent diabetes mellitus. Basic and clinical investigation continues in an attempt to solve the puzzle of pathogenesis, as well as answer questions about the clinical usefulness of microalbuminuria and the appropriate management of hypertension in this population.

Reduction of urinary albumin excretion by thromboxane synthetase inhibitor, OKY-046, through modulating renal prostaglandins in patients with diabetic nephropathy

We evaluated the effects of thromboxane synthetase inhibitor, OKY-046, on urinary albumin and prostaglandin (PG) excretion in 14 patients with non-insulin-dependent diabetes mellitus (NIDDM). Urinary excretion of 6-keto-PGF1 alpha (a stable metabolite of PGI2), TXB2 (a stable metabolite of TXA2) and PGE2 in NIDDM patients was comparable with that in control subjects. However, the urinary 6-keto-PGF1 alpha/TXB2 ratio in NIDDM patients with both micro- and macroalbuminuria was significantly (P less than 0.001) lower than that in the controls. By a single administration of OKY-046 (40 mg, i.v.) to the diabetic patients, urinary TXB2 excretion significantly (P less than 0.05) decreased from 169.7 +/- 23.9 to 140.2 +/- 17.9 ng/gCr, but urinary 6-keto-PGF1 alpha and PGE2 excretion did not change significantly. The urinary 6-keto-PGF1 alpha/TXB2 ratio thus significantly (P less than 0.01) increased from 1.02 +/- 0.13 to 1.73 +/- 0.41 as associated with significant increments in urine volume (P less than 0.05), urinary sodium excretion (P less than 0.01) and creatinine clearance (P less than 0.05). Of 14 diabetic patients, 7 with macroalbuminuria (albumin index exceeding 100 mg/gCr) were orally given OKY-046 (600 mg/day) for 8 weeks. After this period, the urinary albumin index significantly (P less than 0.05) decreased from 524.9 +/- 149.6 to 317.6 +/- 90.6 mg/gCr.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dietary protein restriction on functional renal reserve in diabetic nephropathy

PURPOSE, PATIENTS, AND METHODS

Functional renal reserve in patients with insulin-dependent diabetes mellitus, as determined by the glomerular filtration rate (GFR) response test, is a measure of the capacity of the kidney to increase glomerular filtration in response to the stimulus of a protein meal or amino acid infusion. This 12-month study evaluated the changes in functional renal reserve in eight patients with insulin-dependent diabetes mellitus with nephropathy (micro-albuminuria [greater than or equal to 30 micrograms/minute]) who chronically decreased their dietary protein intake to a mean of 0.6 g/kg/day (Group 1) compared with a group of similar patients (n = 7) who maintained their unusual dietary protein intake (1.0 g/kg/day, Group 2). Patients were evaluated and measurements taken at 3-, 6-, and 12-month intervals. Absolute and percent increases in GFR were calculated from three averaged 1-hour measurements after an 80-g protein test meal.

RESULTS

Although the initial absolute mean rise (14 +/- 12 versus 18 +/- 13 mL/minute/1.73 m2) in GFR and maximal percent rise (16% +/- 16% versus 32% +/- 27%) after the meal did not differ significantly between the two groups, at 12 months, values in the lower protein group increased (27.8 +/- 9.5 mL/minute/1.73 m2 and 54.7% +/- 48.8%), whereas those in the normal protein intake group declined significantly (3.7 +/- 3.6 mL/min-ute/1.73 m2 and 6.5% +/- 6.5%) (p less than 0.05). Both urine urea and microalbuminuria decreased significantly (p less than 0.05) in the low protein group. Unstimulated GFR at the end of 12 months was significantly less (p less than 0.05) in Group 2 (47 +/- 2 mL/minute/1.73 m2) than in Group 1 (71 +/- 21 mL/minute/1.73 m2). The rate of decline in GFR was significantly greater (p less than 0.05) in the normal protein intake group than in the low protein intake group (0.68 +/- 0.4 versus 0.28 +/- 0.15 mL/minute/1.73 m2/month).

CONCLUSIONS

This study indicates that sustained dietary protein restriction can help to preserve renal function, decrease albuminuria, and lower the baseline GFR while maintaining functional renal reserve in patients with insulin-dependent diabetes mellitus.

Altered synthesis of renin in patients with insulin-dependent diabetes: plasma prorenin as a marker predicting the evolution of nephropathy

Plasma active renin (PARC) and plasma total renin (PTRC) were measured in 72 patients with childhood-onset IDDM and 37 control subjects in the supine posture. The diabetic patients were divided into three groups: group A, 55 patients with normoalbuminuria; group B, 11 patients with microalbuminuria; and group C, 6 patients with overt proteinuria. The levels of PTRC were 125 +/- 51, 240 +/- 124 and 580 +/- 285 ng/l in groups A, B and C, respectively; all of which were significantly higher than 114 +/- 33 ng/l in the control subjects. On the other hand, the ratios of plasma active to total renin, ARC/TRC, were 18.1 +/- 12.5, 10.7 +/- 6.7, and 2.9 +/- 1.4% in groups A, B and C, respectively; all of which were in turn significantly lower than 24.8 +/- 8.7% in the control subjects. Among the diabetic groups, PTRC became higher and ARC/TRC became lower in conjunction with the degree of albuminuria. The acute increments of PARC and PTRC during a standing load test were subsequently observed in 7 patients of group A, 5 of group B, 4 of group C, 13 patients with non-diabetic glomerulonephritis, and 6 control subjects. The ratios of increments of PARC to that of PTRC, delta ARC/delta TRC, were 48.3 +/- 22.3, 35.1 +/- 10.4 and 8.4 +/- 8.1% in groups A, B, C, respectively; all of which were significantly lower than 84.2 +/- 48.6% in the control subjects. Patients with non-diabetic glomerulonephritis showed, to a lesser degree, low ratio of delta ARC/delta TRC (60.4 +/- 37.9%) in conjunction with higher level of PTRC (249 +/- 89 ng/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II receptor regulation in anti-glomerular basement membrane nephritis

The expression of the glomerular receptor for angiotensin II (Ang II-R) was examined longitudinally following the induction of anti-glomerular basement membrane (GBM) nephritis in the rat. The specific aim of the project was to determine whether immunologically-induced glomerular injury led to significant abnormalities of the relationship between glomerular Ang II-R and its circulating ligand, Ang II. Scatchard analysis was used to measure Ang II-R on purified glomeruli at selected time intervals over two months following a single dose of sheep anti-rat GBM antibody. Corresponding values for plasma Ang II were determined. Receptor density fell to approximately 50% by 16 hours following the injection of antibody (control 96.4 +/- 9.3 x 10(6); nephritic 52.6 +/- 5.6 x 10(6) receptors/glomerulus; P less than 0.001) and there was a corresponding threefold increase in plasma Ang II (control 21.0 +/- 2.5; nephritic 66.6 +/- 20.6 pg/ml; P less than 0.01). However, this reduction in receptor binding could not be explained by the rise in plasma Ang II concentration, as effective blockade of the RAS by enalapril did not alter receptor expression (56.1 +/- 4.6 x 10(6) receptors/glomerulus). Subsequently, a rise in receptor density and a corresponding fall in plasma Ang II were observed: three days after antibody administration, receptor concentration had increased significantly above control values (150.5 +/- 11.9 x 10(6] while plasma Ang II was undetectable (that is, less than 5 pg/ml). Ang II-R remained elevated for the next two weeks but returned to normal four to eight weeks after the administration of nephrotoxic antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiproteinuric effect of captopril in a patient with lupus nephritis and intractable nephrotic syndrome

A 22 year old woman presented with lupus nephritis, hypertension, and intractable nephrotic syndrome. Albumin and furosemide given intravenously was ineffective. Captopril administered in a daily dose of 62.5 mg was associated with a reduction in proteinuria from 28 g/24 hours to 11.5 g/24 hours over 10 weeks, resulting in a weight reduction of 16 kg. This was achieved with relative preservation of renal function. Captopril should be considered in the treatment of intractable proteinuria in patients with lupus nephritis, or when cytotoxic drugs are refused, because of its efficacy and relative safety. Captopril should, however, be used as an adjunct and not as a substitute for standard treatment.

Effect of dietary protein on the renin-angiotensin system in subtotally nephrectomized rats

Dietary protein restriction improves the course of renal disease in the remnant kidney model. Dietary protein restriction can also reduce plasma renin activity in several circumstances. We examined the interaction between dietary protein and the renin-angiotensin system in subtotally nephrectomized rats (1-2/3 nephrectomy). No difference was seen in tissue renin activity in rats ingesting a high (30%) versus a low (6%) protein diet. To determine the pathophysiological role of angiotensin II in subtotally nephrectomized rats, we examined the acute renal response to an intrarenal infusion of the angiotensin II antagonist Sar1 Gly8-angiotensin II (10 micrograms/kg/min). Only those subtotally nephrectomized animals ingesting a high protein diet exhibited a consistent improvement in glomerular permselectivity, as manifested by a 24% fall in the fractional clearance of albumin (basal 16.19 +/- 3.65 x 10(-4) vs. Sar1 Gly8-AII 12.26 +/- 3.21 x 10(-4); P less than 0.02) and a 19% fall in the fractional clearance of IgG (basal 3.75 +/- 0.67 x 10(-4) vs. Sar1 Gly8-AII 3.03 +/- 0.48 x 10(-4); P less than 0.02). No consistent change occurred in glomerular permselectivity in the rats on the low protein diet or rats infused with vehicle only. No change in mean arterial pressure or whole-kidney hemodynamics were seen with angiotensin II blockade. Decrements in SNGFR and glomerular capillary pressure occurred with angiotensin blockade in the animals ingesting the high protein diet, suggesting hemodynamic factors as a mechanism for the improvement in permselective defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Enalapril reduces microalbuminuria in young normotensive type 1 (insulin-dependent) diabetic patients irrespective of its hypotensive effect

The effect of enalapril on albumin excretion rate was studied in two groups of age- and sex-matched Type 1 (insulin-dependent) diabetic patients, aged 15-20 years, with persistent microalbuminuria greater than 20 micrograms/min. Group 1 contained six patients with systolic blood pressure greater than or equal to 75th percentile for age and sex, group 2 six normotensive patients. Enalapril (10-20 mg/day) was given for six months. Albumin excretion rate, glomerular filtration rate, renal plasma flow, blood pressure at rest and during exercise, and angiotensin converting enzyme activity were measured before, after three weeks' and six months' treatment and six months after treatment withdrawal. Albumin excretion rate decreased in all patients after three weeks' (mean decreases 55% in group 1, 65% in group 2) and six months' treatment (35% in group 1, 61% in group 2). Systolic blood pressure remained unchanged in both groups. Diastolic pressure was reduced after three weeks in group 1 (p = 0.001). No reduction in increment in systolic pressure during exercise test occurred in any group during treatment. Angiotensin converting enzyme activity decreased in all patients after three weeks (p = 0.001) and six months (p = 0.003). This correlated to the decrease in albumin excretion rate after three weeks (r = 0.79, p = 0.05) and six months (r = 0.59, p = 0.04). HbA1c, mean blood glucose and glomerular filtration rate remained unchanged during the study in both groups. Renal plasma flow tended to increase after three weeks' and six months' treatment in group 2 (p = 0.06, respectively) but not in group 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin converting enzyme inhibitor therapy to decrease microalbuminuria in normotensive children with insulin-dependent diabetes mellitus

It has been proposed that lowering glomerular pressure in children with insulin-dependent diabetes mellitus will reduce microalbuminuria and that this reduction may preserve renal function. We therefore conducted a double-blind, placebo-controlled, crossover trial to compare 3 months of treatment with the angiotensin converting enzyme inhibitor captopril (0.9 mg/kg/day), and 3 months of placebo administration to 12 normotensive adolescents with insulin-dependent diabetes mellitus, 11 with microalbuminuria (albumin excretion rate of 15 to 200 micrograms/min) and one with early overt nephropathy. Mean age (+/- SD) was 14.4 +/- 1.7 years, and disease duration was 5.1 +/- 2.5 years. Albumin excretion rate decreased significantly during captopril therapy (baseline 78 +/- 114 micrograms/min; mean of monthly measurements 38 +/- 55 micrograms/min vs placebo 78 +/- 140 micrograms/min; p less than 0.001). During captopril therapy, albumin excretion was reduced by 41 +/- 44% and decreased in 10 of 12 subjects, but was unchanged in two, one with a borderline albumin excretion rate (16.3 micrograms/min) and one with diabetes of short duration (2.9 years). Plasma renin activity rose significantly during captopril therapy, and mean arterial pressure decreased slightly (placebo 81 +/- 7 mm Hg; captopril 76 +/- 5 mm Hg; p = 0.004). After 3 months of captopril treatment, glomerular filtration rate and renal plasma flow did not change significantly. Hemoglobin Alc values remained stable during the study. The only side effect of captopril was diarrhea in one patient. We conclude that, in the short term, captopril is effective in decreasing albumin excretion rate in normotensive children with insulin-dependent diabetes mellitus and microalbuminuria, without significant side effects. Longer trials are indicated in an attempt to delay or prevent overt nephropathy.

Mechanisms of diabetic renal and cardiovascular disease

The precise pathogenesis of human diabetic kidney disease and the factors responsible for the susceptibility to it remain to be established. However, there is now evidence that renal disease clusters in families and that genetic factors are of central importance in determining liability. A predisposition to arterial hypertension has been suggested as playing a contributory role in the development of kidney disease. Genetically controlled hypertrophic processes may be implicated in the susceptibility to arterial wall damage and glomerular injury in diabetes. This suggestion derives from the observation that the fibroblasts of patients with diabetic nephropathy show a higher Na+/H+ antiport activity and a greater 3H-thymidine incorporation into DNA than fibroblasts of diabetic patients without nephropathy. The first sign of renal damage is the appearance of microalbuminuria and of a small elevation in arterial pressure, changes associated with significant mesangial expansion. Microalbuminuria is associated with abnormalities of lipoprotein profiles possibly as a consequence of insulin-resistance-induced hyperinsulinemia. It could be postulated that the environmental changes brought about by diabetes lead in susceptible individuals to increased systemic and intraglomerular pressure on the one hand and mesangial expansion on the other. These two processes would cause proteinuria and glomerulosclerosis. Lipid abnormalities would further aggravate the renal histological damage and, in combination with hypertension, contribute to the accelerated atherosclerosis typical of patients with diabetic kidney disease. A vicious circle would thus be triggered of reduction in renal function, more hypertension, more proteinuria, more glomerular obsolence, more hyperlipidemia and eventually end-stage renal failure or premature cardiovascular death.

Renal protective effects of angiotensin-converting enzyme inhibition

Nephron loss is a common progression of a diverse range of kidney diseases. Recent experimental models of chronic renal disease have suggested that hemodynamic and nonhemodynamic mechanisms play key roles in progressive renal injury. Extensive renal ablation in the rat was followed by development of altered glomerular hemodynamics. Albuminuria and histologic damage leading to focal glomerulosclerosis were preceded by the development of increased glomerular pressures and were prevented by interventions such as severe dietary protein restriction and angiotensin-converting enzyme (ACE) inhibitor therapy. Both experimental interventions ameliorated glomerular hypertension. It was therefore concluded that these interventions ameliorated injury by glomerular hemodynamic effect. Similar findings were obtained in a rat model of type I diabetes mellitus induced by streptozotocin in which glomerular hemodynamic factors appeared important to the development of progressive renal disease. Recent studies have suggested that nonhemodynamic factors have important roles in the progression of glomerular injury. For example, although the predominant effects of ACE inhibitor therapy appear to be hemodynamically mediated, data are emerging which suggest that these agents may also influence growth/proliferation of glomerular cells. Because hyperplasia/hypertrophy may influence glomerular susceptibility to injury, this may also be a potential mechanism whereby ACE inhibitor therapy influences glomerular damage. In addition, a variety of studies have suggested that hyperlipidemia, which is frequent accompaniment of glomerular disease, is an important modulator of glomerular injury independent of glomerular hemodynamic effects. Coagulation factors, calcium phosphorus balance, as well as the genetic susceptibility of the glomerulus to injury, all appear to contribute to progressive nephron destruction.

Angiotensin-converting enzyme inhibitors: a comparative review

The chemistry, pharmacology, pharmacokinetics, adverse effects, and dosages of the three currently available angiotensin-converting enzyme (ACE) inhibitors are reviewed. This class of agents effectively inhibits the conversion of angiotensin I to the active vasoconstrictor angiotensin II, a hormone that also promotes, via aldosterone stimulation, increased sodium and water retention. The ACE inhibitors, therefore, are capable of lowering blood pressure primarily by promoting vasodilatation and reducing intravascular fluid volume. Captopril, the first orally active, commercially available ACE inhibitor, is a sulfhydryl-containing compound. Captopril was followed by the introduction of enalapril and lisinopril, two non-sulfhydryl ACE inhibitors. The pharmacokinetic profiles of these three ACE inhibitors differ. Captopril has rapid onset with relatively short duration of action, whereas enalapril and lisinopril have slower onset and relatively long duration of action. Captopril is an active ACE inhibitor in its orally absorbable parent form. In contrast, enalapril must be deesterified in the liver to the metabolite enalaprilat in order to inhibit the converting enzyme; this accounts for its delayed onset of action. Lisinopril does not require metabolic activation to be effective; however, a slow and incomplete absorption pattern explains the delay in onset of activity. Captopril and its disulfide metabolites are primarily excreted in the urine with minor elimination in the feces. Approximately two-thirds of an administered enalapril dose is excreted in the urine as both the parent drug and the metabolite enalaprilat; the remainder of these two substances are excreted in the feces. Lisinopril does not undergo measurable metabolism and approximately one-third is excreted unchanged in the urine with the remaining parent drug being excreted in the feces. The ACE inhibitors lower systemic vascular resistance with a resultant decrease in blood pressure. Their efficacy is comparable to diuretics and beta-blockers in treating patients with mild, moderate, or severe essential and renovascular hypertension. In those patients with severe congestive heart failure (CHF) the ACE inhibitors produce a reduction in systemic vascular resistance, blood pressure, pulmonary capillary wedge pressure, and pulmonary artery pressure. These drugs may produce improvement in cardiac output and stroke volume and, with chronic administration, may promote regression of left ventricular hypertrophy. The antihypertensive effects of the ACE inhibitors are enhanced when these agents are combined with a diuretic. Captopril and enalapril have been shown to be of particular benefits as adjunctive therapy in patients with congestive heart failure, both in terms of subjective improvement of patient symptoms, and in improving overall hemodynamic status.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of captopril and enalapril in the treatment of hypertension in patients with non-insulin dependent diabetes mellitus and nephropathy

Eighteen patients with non-insulin dependent diabetes mellitus (NIDDM), hypertension and nephropathy were randomized to receive captopril or enalapril for 6 months. Two patients with serum creatinine of greater than 400 mumol/l had to be excluded from the study because of rapidly deteriorating renal function after starting treatment. Of the remaining patients, 7 received captopril and 9 received enalapril. Blood pressure control was achieved in about 50% of patients with either drug alone. Serum creatinine and creatinine clearance were unchanged in both groups but there was a greater tendency for the former to increase in patients with higher pretreatment values. Proteinuria was reduced at 1 month only in the enalapril group which also showed a significant elevation of serum potassium after treatment. Captopril and enalapril have only a modest antihypertensive action in patients with NIDDM and nephropathy. Their use in patients with renal insufficiency must be balanced against the risk of further aggravating the deterioration of renal function.

Angiotensin-converting enzyme inhibitors and renal function

The effects of angiotensin-converting enzyme (ACE) inhibitors on renal hemodynamics vary widely depending on the preexisting physiologic and pathologic state of the kidneys. Although some studies of ACE inhibitors in primary essential hypertension have demonstrated increases in glomerular filtration rate (GFR) and effective renal plasma flow in patients with renal impairment, other studies have not shown these same beneficial results. The difference may involve the choice of ACE inhibitor used in the investigations, but controlled comparison trials are needed to determine whether this is the case. The use of ACE inhibitors in renovascular hypertension remains controversial. ACE inhibition can interfere with the autoregulation of GFR mediated by angiotensin II and may lead to deterioration of renal function, especially in patients with bilateral renal artery stenosis or stenosis of a solitary kidney. Additionally, ACE inhibitors have been shown to cause a decline in GFR in the kidney affected by the stenosis, whether or not clinically apparent renal insufficiency occurs. Although the functional impairment associated with ACE inhibitors in renal artery stenosis has generally been reversible following removal of the drug, the consequences of a long-term reduction in GFR are unknown. Treatment of stable congestive heart failure (CHF) with ACE inhibitors can result in enhancement of GFR and reduction of sodium and fluid retention, thus improving the clinical state. However, in patients with decompensated cardiac failure, renal perfusion pressures may already be at or near the autoregulatory breakpoint and ACE inhibition may cause deterioration of renal function. In general, ACE inhibitors can be used safely in CHF if they are initiated cautiously, with adjustment of ACE inhibitor and diuretic dosages to avoid systemic hypotension and sodium and fluid depletion. In studies comparing the agents, enalapril and lisinopril have both been shown to cause higher incidences of renal function deterioration than has captopril. These findings suggest that the more complete or sustained ACE inhibition seen with the longer-acting agents may be detrimental to renal function in patients with CHF. The use of ACE inhibitors in the treatment of proteinuria is the newest area of research with these agents. At present it appears that ACE inhibitors reduce urinary protein excretion the most effectively in diabetic patients with mild proteinuria and in hypertensive patients with renal insufficiency and proteinuria due to glomerular disorders. More study is needed to determine whether these agents can reduce the rate of renal failure progression and to define the patient populations expected to benefit most.(ABSTRACT TRUNCATED AT 400 WORDS)

Contrasting effects of enalapril and metoprolol on proteinuria in diabetic nephropathy

OBJECTIVE

To assess whether angiotensin converting enzyme inhibition reduces proteinuria in diabetic nephropathy more than blood pressure reduction with other antihypertensive treatment.

DESIGN

Prospective, open randomised study lasting eight weeks in patients with diabetic nephropathy.

SETTING

Outpatient nephrology clinics.

PATIENTS

40 Patients with type I diabetes and diabetic nephropathy with reduced renal function.

INTERVENTION

Antihypertensive treatment with enalapril or metoprolol, usually combined with frusemide.

MAIN OUTCOME MEASURES

Arterial blood pressure and urinary excretion of albumin and protein.

RESULTS

Arterial blood pressure after eight weeks was 135/82 (SD 13/7) mm Hg in the group given enalapril and 136/86 (16/12) mm Hg in the group given metoprolol. Proteinuria and albuminuria were similar in both groups before randomisation. After eight weeks' treatment, the geometric mean albumin excretion was 0.7 (95% confidence interval 0.5 to 1.2) g/24 h in the patients given enalapril and 1.6 (1.1 to 2.5) g/24 h in the patients given metoprolol (p less than 0.02). The proteinuria was 1.1 (0.7 to 1.7) and 2.4 (1.6 to 3.6) g/24 h respectively (p less than 0.02).

CONCLUSIONS

Antihypertensive treatment with enalapril reduced proteinuria in patients with diabetic nephropathy more than an equally effective antihypertensive treatment with metoprolol. This points to a specific antiproteinuric effect of the angiotensin converting enzyme inhibitor independent of the effect on systemic blood pressure.

Renal effects of angiotensin converting enzyme inhibitors: nondiabetic chronic renal disease

Based on studies in the rat remnant kidney model, it has been proposed that glomerular hypertension is responsible for the progressive nature of chronic renal disease. In that model, therapy with angiotensin converting enzyme (ACE) inhibitors reduced glomerular pressures. As a result, glomerular injury was reduced and the rate of progression of renal disease was slowed. Thus, alterations in hemodynamics may play an important role in glomerular injury. However, it is now evident that a variety of metabolic and other factors affect the progression of renal disease. Moreover, recent studies suggest that ACE inhibitors may also have beneficial effects that are independent of alterations in glomerular pressure. In humans, the glomerular hemodynamic response to renal disease cannot be measured, and it is not known whether or under which conditions glomerular capillary pressure might be elevated. Treatment with ACE inhibitors safely lowers blood pressure without adversely affecting renal function in most patients with nondiabetic chronic renal failure. Although proteinuria and the rate of progression of renal disease may decrease in some patients, these effects are inconsistently seen. Identification of the factors that modulate this variability in response to ACE inhibition may provide new insight into the pathogenesis and treatment of progressive renal disease in humans.

Reduction of albuminuria after angiotensin converting enzyme inhibition in various renal disorders

The urinary albumin excretion measured by the albumin creatinine clearance ratio (Calb/Ccreat) and the mean supine arterial blood pressure (MAP) were studied before the start of ACE inhibition, at the start and during up to 1 year of ACE inhibition with Captopril or Enalapril in 35 patients with various chronic proteinuric renal disorders with or without renal failure, arterial hypertension and nephrotic syndrome. Before the start of ACE inhibition mean Calb/Ccreat, MAP, s-albumin and s-creatinine did not change. During ACE inhibition the Calb/Ccreat was reduced from 75% (p less than 0.05) in patients with minimal albuminuria to 41% (p less than 0.005) in patients with extensive albuminuria. Average reduction of albuminuria was 44% at one year's observation time. Serum albumin increased 9% (p less than 0.05), serum creatinine did not change significantly and MAP showed a slight, not uniformly significant decrease. The reduction of Calb/Ccreat was of the same order in the different renal disorders studied and was independent of the renal function, presence or absence of nephrotic syndrome and treatment with antihypertensive or immunosuppressive drugs. The decrease in Calb/Ccreat during ACE inhibition was related to the reduction in MAP at most time intervals, but Calb/Ccreat decreased also when MAP was unchanged or increased. Thus the decrease in Calb/Ccreat during ACE inhibition does not only seem to be a consequence of a decrease in the systemic arterial blood pressure but reasonably also due to changes in the intra-renal hemodynamics and most probably a decrease in the glomerular capillary pressure.

Perindopril. A review of its pharmacokinetics and clinical pharmacology

Perindopril is an orally active, non-thiol angiotensin-converting enzyme (ACE) inhibitor, which in doses of 4 to 8mg is effective in the control of essential hypertension. As monotherapy it is as effective as once-daily atenolol and possibly more effective than twice-daily captopril. A synergistic response has been noted when perindopril is combined with a thiazide diuretic. Maximal pharmacodynamic effects (ACE inhibition, increase in plasma renin activity and angiotensin I, reduction in aldosterone and angiotensin II and blood pressure) are seen 4 to 6 hours after dosing, with substantial effects still present at 24 hours. Perindopril is a prodrug which requires de-esterification to perindoprilat for useful ACE inhibition. Maximal plasma perindoprilat concentrations are reached 2 to 6 hours after oral administration of perindopril, and 70% of the active metabolite is cleared by the kidneys. The other major metabolite of perindopril is an inactive glucuronide. Ageing is associated with increased serum perindoprilat concentrations, which are probably caused by a combination of enhanced conversion to the active metabolite and diminished renal clearance. Compensated cirrhosis does not appear to have an independent effect. There is little published experience of the use of perindopril in patients with cardiac failure or other cardiac disease, but preliminary evidence would support the general value of this class of agent as adjunctive therapy.

ACE inhibitors. A safe option for hypertension and congestive heart failure

The Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure has recently recommended angiotensin-converting enzyme (ACE) inhibitors, beta blockers, and diuretics as potential first-step agents for the pharmacologic treatment of hypertension. ACE inhibitors should be considered an important option in most patients because of their safety profile, absence of adverse metabolic effects, and positive cardiac and renal effects. If the response to an ACE inhibitor is inadequate, a diuretic or another agent can be added, and this combination should be effective and well tolerated in 85% to 90% of patients. ACE inhibitors can be used to treat congestive heart failure and to prevent the renal complications of hypertension and diabetes mellitus, significantly expanding their use in patients with these high-risk conditions. They also can be used concurrently with other antihypertensive agents, digitalis, cardiac glycosides, and lithium and are not contraindicated in most of the diseases commonly seen in hypertensive patients.

Initial therapy for hypertension--individualizing care

Of the approximately 58 million Americans with hypertension, the majority have only mild increases in blood pressure and individually are at low risk. Large group studies, however, have demonstrated the efficacy of treating mild hypertension. Public health efforts during the past 16 years have increased the number of hypertensive patients made aware of their condition and brought into treatment. A major problem, however, is consistently maintaining patients on long-term therapy. A large number of nonpharmacologic and pharmacologic treatments have become available for the management of hypertension. These treatments must be applied individually to enhance benefit, minimize potential harm, and increase the likelihood of long-term compliance for what is often a lifelong disorder. For accomplishing this goal, a thorough understanding of important characteristics of both the individual patient and the available therapeutic modalities is needed.

General considerations in selecting antihypertensive agents in patients with type II diabetes mellitus and hypertension

The Working Group on Hypertension in Diabetes recommends starting pharmacologic treatment of hypertension with a small dose of a thiazide, beta-blocker, prazosin hydrochloride, angiotensin-converting enzyme inhibitor, or calcium channel blocker. Thus, these alternatives are regarded as first-line treatment in hypertensive patients with diabetes mellitus. Both thiazides and beta-blockers can cause deterioration in glycemic control and have an unfavorable influence on the lipoprotein profile. These metabolic side effects may partly counteract beneficial effects. Non-selective beta-blockers should probably be avoided in diabetic patients, since blockade of the beta-2 receptor may be associated with a compromise in peripheral blood flow and with problems associated with hypoglycemia. Cardioselective beta-blockers, which may have primary preventive effects on coronary disease, are beneficial in this patient group. In patients with non-insulin-dependent diabetes mellitus without nephropathy or overt fluid retention, diuretic therapy could be replaced by sodium restriction and/or calcium channel blocker therapy, since these agents also have a mild diuretic effect. Calcium channel blockers, angiotensin-converting enzyme inhibitors, and prazosin hydrochloride have minimal metabolic side effects, making them suitable for treatment of hypertension in this patient group.

The epidemiology of diabetic nephropathy

Many areas of information in the epidemiology of diabetic nephropathy are lacking, but multiple studies designed specifically to answer these questions are currently being conducted. In the next 5-10 years, our current understanding of the epidemiology of diabetic nephropathy may either be confirmed or discredited. In the meantime, clinicians should use the data available to make decisions about treatment and should focus on the modifiable factors of glucose and blood pressure control in both IDDM and NIDDM, especially in patients with low-level albuminuria or clinical proteinuria.

Effect of converting enzyme inhibition on the course of adriamycin-induced nephropathy

The effect of the converting enzyme inhibitor (CEI) enalapril was assessed in Munich-Wistar rats with established adriamycin nephrosis. Rats were given a single dose of adriamycin and one month later divided into four groups matched for albuminuria, blood pressure, and plasma albumin concentration. Groups 1 and 3 remained untreated while groups 2 and 4 received enalapril. Groups 1 and 2 underwent micropuncture studies after 10 days. These short-term studies showed that enalapril reduced arterial blood pressure (101 +/- 2 vs. 124 +/- 3 mm Hg, group 2 vs. 1, P less than 0.05) and glomerular capillary pressure (54 +/- 1 vs. 61 +/- 2 mm Hg, P less than 0.05) without reducing albuminuria (617 +/- 50 vs. 570 +/- 47 mg/day) or GFR (1.03 +/- 0.04 vs. 1.04 +/- 0.11 ml/min). Groups 3 and 4 were studied at four and at six months to assess the effect of enalapril on progression of renal injury in adriamycin nephrosis. Chronic enalapril treatment reduced blood pressure without reducing albuminuria in group 4. Untreated group 3 rats exhibited a progressive reduction in GFR (0.35 +/- 0.08 ml/min at 4 months, 0.27 +/- 0.07 ml/min at 6 months). Enalapril treatment blunted but did not prevent reduction in GFR in group 4 (0.86 +/- 0.15 ml/min at 4 months, 0.69 +/- 0.13 ml/min at 6 months, both P less than 0.05 vs. group 3). Reduction in GFR was associated with the development of glomerular sclerosis in both treated and untreated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Short and long term effects of antihypertensive therapy in the diabetic rat

To compare the impact of differing antihypertensive regimens on the development of renal injury, studies were performed in three groups of moderately hyperglycemic diabetic rats, and one group of non-diabetic control (C) rats. One diabetic group (DM) received no therapy except insulin. The remaining diabetic groups received insulin and either the angiotensin I converting enzyme inhibitor captopril (CAP), or triple therapy (TRX) with reserpine, hydralazine and hydrochlorothiazide. CAP and TRX modestly and comparably lowered blood pressure. At 6 to 10 weeks, DM rats exhibited elevation of the single nephron glomerular filtration rate (SNGFR), due to elevations of the glomerular capillary plasma flow rate (QA) and the glomerular capillary hydraulic pressure (PGC). In both DM/CAP and DM/TRX rats, blood pressure reduction was associated with selective normalization of PGC, without change in SNGFR or QA. In long-term (70 weeks) studies, DM rats exhibited progressive albuminuria and marked glomerular sclerosis. CAP limited albuminuria and injury to values even lower than those in C rats, whereas TRX served only to delay, but not to prevent, the increase in albuminuria. TRX reduced glomerular sclerosis, but was less effective than CAP. At 70 weeks, CAP and TRX still reduced systemic blood pressure; PGC remained at normal levels with CAP but was no longer controlled with TRX. These results confirm the clinical observation that antihypertensive therapy slows diabetic glomerulopathy, but also suggest that CAP affords superior long-term protection as compared to the other antihypertensive drug regimen studied.

Effect of captopril on blood pressure and kidney function in normotensive insulin dependent diabetics with nephropathy

OBJECTIVE

To assess whether inhibition of angiotensin converting enzyme protects kidney function in diabetic nephropathy.

DESIGN

Open, randomised follow up study of normotensive insulin dependent diabetics with nephropathy either treated or not with captopril for one year.

SETTING

Outpatient diabetic clinic in a tertiary referral centre.

PATIENTS

32 Normotensive patients with insulin dependent diabetes complicated by nephropathy who were randomised either to the treatment group (n = 15) or to the control group (n = 17).

INTERVENTIONS

The treatment group was given captopril (25-100 mg/day) for 12 months, the average dose during the second six months of the study being 40 mg daily. Controls were not treated.

MAIN OUTCOME MEASURES

Albuminuria, arterial blood pressure, and the glomerular filtration rate.

RESULTS

Mean arterial blood pressure fell by 3 (SE 2) mm Hg in the captopril treated group and rose by 6 (1) mm Hg in the controls. In addition, albuminuria declined by 11% in the captopril treated group and rose by 55% in the controls, fractional albumin clearance fell by 17% in the captopril treated group and increased by 66% in the controls, and the glomerular filtration rate declined by 3.1 (2.8)ml/min/1.73 m2 with captopril and by 6.4 (3.1) ml/min/1.73 m2 in the controls.

CONCLUSION

Inhibition of angiotensin converting enzyme arrests the progressive rise in albuminuria in normotensive insulin dependent diabetics with nephropathy.

Efficacy and variability of the antiproteinuric effect of ACE inhibition by lisinopril

We studied the efficacy of the ACE inhibitor lisinopril in treating overt proteinuria in comparison with the NSAID indomethacin, and evaluated some of the conditions that could influence this antiproteinuric effect. In 12 patients with a proteinuria varying from 3.2 to 10.5 g/24 hr, a diastolic BP ranging from 64 to 105 mm Hg, and a GFR varying from 34 to 127 ml/min, the effect of different lisinopril doses and of changing dietary sodium intake was evaluated. Proteinuria fell by 27 +/- 20% from 6.1 +/- 2.1 to 4.5 +/- 1.9 g/24 hr on a low dose (median 5 mg/day) lisinopril and by 50 +/- 17% to 3.1 +/- 1.4 g/24 hr on a higher dose (median 10 mg/day), irrespective of initial proteinuria, BP, or GFR. This antiproteinuric effect was abolished by increasing salt intake from 50 to 200 mmol/day, and was recovered again by re-instituting the sodium restricted diet. The antiproteinuric effect of 10 mg/day lisinopril was comparable to the reduction in proteinuria (by 57 +/- 21% to 2.8 +/- 2.0 g/24 hr) on 150 mg/day indomethacin, while adverse effects were less and renal hemodynamic effects were more favorable during lisinopril. In some patients it took several weeks before the effect of the ACE inhibitor on proteinuria was stabilized. Thus, the antiproteinuric effect of the ACE inhibitor lisinopril appears to be dose and time related, and is strongly dependent on dietary sodium restriction, whereas it does not depend on initial proteinuria, BP, or GFR. The effect is comparable to that of indomethacin, while adverse effects are less.