Effect of enalapril on haemoglobin and serum erythropoietin in patients with chronic nephropathy

ACE inhibitors do not induce recombinant human erythropoietin resistance in hemodialysis patients

Angiotensin-converting enzyme (ACE) inhibitors may exacerbate anemia in patients with chronic renal failure, as well as in dialysis patients. To better answer this question, a prospective, crossover study was conducted to evaluate the effect of ACE inhibitors on recombinant human erythropoietin (rHuEPO) requirements in hemodialysis patients. Patients administered an ACE inhibitor when entering the study remained on this drug for the initial 4 months and were then switched to another antihypertensive agent for 4 more months. Patients not initially administered an ACE inhibitor were switched to lisinopril at 4 months. rHuEPO doses were adjusted using a sliding scale based on weekly laboratory hematocrit values. The inclusion criteria were met by 51 patients undergoing dialysis. Demographics were as follows: 61% were women, 64% were black, 46% had diabetes, average age was 53.2 +/- 13.3 years, and time on hemodialysis was 38.0 +/- 44.5 months. Thirty-three patients completed the study. Hematocrit averaged 32.7% +/- 1.9% while on ACE inhibitor therapy and 33.1% +/- 2.1% off ACE inhibitor therapy (P = 0.217). There was no difference in rHuEPO dose per treatment during each period (3,500 +/- 1,549 U on ACE inhibitor therapy versus 3,312 +/- 1,492 U off ACE inhibitor therapy; P = 0.300). No significant differences were found in degree of blood pressure control or various clinical and laboratory parameters that might be associated with rHuEPO resistance between the two periods. Similarly, no differences were found in hospitalization days, duration of infections, or transfusion requirements. These findings suggest that ACE inhibitors do not contribute to rHuEPO resistance in hemodialysis patients.

The impact of withdrawing ACE inhibitors on erythropoietin responsiveness and left ventricular hypertrophy in haemodialysis patients

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors have the capability of decreasing left ventricular mass index (LVMI) in chronic haemodialysis (HD) patients. On the other hand, recent reports provide conflicting information regarding the impact of ACE inhibitors on responsiveness to recombinant human erythropoietin (rHuEpo), and there are no data about the effect of withdrawing ACE inhibitors both on rHuEpo response and LVMI in HD patients.

METHODS

ACE inhibitors were switched to another antihypertensive medication in 23 out of 68 patients in our HD unit who were receiving both rHuEpo and an ACE inhibitor for more than 1 year. Blood pressure at the pre- and post-dialysis phases, haematocrit levels and rHuEpo doses were determined at the end of the first and of the third years, and the LVMI was determined at the end of the third year. Statistical analyses were done in 15 patients in whom the study could be completed.

RESULTS

The mean (+/-SD) haematocrit level was increased from 26.3+6.4% to 29.8+/-6.3% at the first year (P<0.05), and to 29.4+/-6.5% at the third year (P<0.05 vs before), while the mean dose of rHuEpo was decreased from 208.3+/-99.0 UI/kg/week to 141.0+/-91.8 at the first year (P=0.01), and to 141.4+/-81.0 at the third year (P=0.01 vs before). Administration of rHuEpo had been stopped in two patients at the end of the first year. The mean blood pressure level and the mean LVMI were not changed (P>0.05 vs before). There were no significant changes in dialysis parameters, iron status, plasma renin activities, and levels of aldosterone, intact parathyroid hormone, aluminum and erythropoietin.

CONCLUSION

The findings of this small uncontrolled study indicate that withdrawal of ACE inhibitors in hypertensive chronic HD patients receiving rHuEpo may result in an increase in haematocrit level, and a decrease in dose of rHuEpo without any significant changes in the blood pressure level and LVMI. Controlled prospective studies are needed to clarify this issue.

Interference of angiotensin-converting enzyme inhibitors on erythropoiesis in kidney transplant recipients: role of growth factors and cytokines

BACKGROUND

Recent data indicate that factors other than erythropoietin (EPO), such as insulin-like growth factor 1 (IGF-1), can promote erythropoiesis in vitro and correct the anemia of chronic renal failure in vivo. IGF-1 is produced by the liver under growth hormone control, as well as by other sources, including the kidney. The erythropoietic role of growth factors and cytokines and their possible modulation by angiotensin-converting enzyme inhibitors (ACEI) has never been explored.

METHODS

This study evaluated the serum levels of EPO, IGF-1, interleukin (IL)-2, IL-3, and granulocyte macrophage-colony-stimulating factor in 40 kidney transplanted patients with or without posttransplant erythrocytosis (PTE) and in 10 living kidney donors. Then, the effect of ACEI therapy on the above pattern was examined in patients with PTE.

RESULTS

EPO and IGF-1 serum levels were significantly higher in patients with PTE than in patients without PTE and in living kidney donor subjects. ACEI therapy significantly reduced hematocrit (Hct) as well as circulating IGF-1 and EPO levels. Of note, the decrease in IGF-1 was prominent mainly in those patients whose EPO levels were not significantly modified by ACEI therapy. In all of the patients Hct levels displayed a direct relationship with circulating IGF-1 levels, but not with EPO concentration. Growth hormone did not significantly differ among the groups examined, whereas it steeply increased under ACEI. Finally, no significant difference in IL-2, IL-3, and granulocyte macrophage-colony-stimulating factor serum levels was detected.

CONCLUSIONS

IGF-1 seems to play a role in the ACEI-related decrease of Hct in patients with PTE, chiefly in patients without any modification of EPO serum levels.

Efficacy of enalapril after ineffective theophylline treatment on erythrocytosis after renal transplantation

Erythrocytosis represents a common complication in renal allograft recipients. Traditional therapies including phlebotomy and bilateral native nephrectomies are cumbersome for both the clinical personnel and the patient. Recently, pharmacological agents such as angiotensin converting enzyme inhibitor and theophylline have been proposed as effective therapies for post-transplant erythrocytosis (PTE). We have treated a PTE patient successfully with enalapril without any side effects and renal dysfunction after theophylline treatment showed no improvement in PTE. A decline in Ht levels was independent of the changes in Epo levels during enalapril treatment. Although the mechanism underlying the beneficial effect of enalapril remains undetermined, enalapril is recommended for the initial treatment of PTE.

Angiotensin-converting enzyme inhibitor therapy in chronic hemodialysis patients: any evidence of erythropoietin resistance?

Exacerbation of anemia associated with angiotensin-converting enzyme (ACE) inhibitor therapy has been noted to occur in patients with chronic renal failure, end-stage renal disease, and renal transplantation. Angiotensin-converting enzyme inhibitors appear to cause anemia through induction of decreased red blood cell production. There are data suggesting that ACE inhibitors may impair erythropoiesis via either suppression of angiotensin-mediated erythropoietin (EPO) production or bone marrow response to EPO. Patients on chronic hemodialysis receive recombinant human EPO (rHuEPO) for therapy of anemia and may also receive an ACE inhibitor for hypertension or congestive heart failure. We undertook a retrospective study to evaluate whether patients treated with ACE inhibitors developed a more severe anemia or required a higher dose of rHuEPO to maintain a similar hematocrit. Ninety-five of 108 chronic hemodialysis patients met study criteria (hemodialysis for 4 months and no treatment with an ACE inhibitor for at least 4 months = group 1; therapy with an ACE inhibitor for at least 4 months = group 2). Forty-eight patients (group 1, n = 24; group 2, n = 24) were available for analysis after exclusion for a variety of factors. There was no difference between the two groups in terms of baseline characteristics, number of blood transfusions or hospital days, or other laboratory parameters. There was no statistically significant difference in average hematocrit between group 1 (33.5% +/- 3.9%) and group 2 (32.6% +/- 1.6%). Similarly, no significant difference was observed for the average rHuEPO dose/treatment between group 1 (3,272 +/- 1,532 IU/treatment; 50.69 +/- 26.94 IU/kg/treatment) and group 2 (3,401 +/- 1,009 IU/treatment; 52.87 +/- 19.38 IU/kg/treatment). These results suggest that ACE inhibitors do not significantly induce more severe anemia or alter rHuEPO response in chronic hemodialysis patients.

Mechanism of angiotensin converting enzyme inhibitor-related anemia in renal transplant recipients

To delineate the pathogenesis of the reduction in hemoglobin occurring in renal transplant patients treated with angiotensin converting enzyme inhibitors (ACEI) and azathioprine (AZA) a controlled, prospective trial of ACEI withdrawal was conducted. The ACEI was replaced by nifedipine or clonidine in 15 kidney transplant patients immunosuppressed with AZA and prednisone (enalapril in 14 and captopril in 1). Before and during 10 to 12 weeks after withdrawal of the ACEI, AZA metabolites, renal function parameters and hematological parameters including erythropoietin and reticulocytes were evaluated. Enalaprilat levels were measured and compared with 15 similar patients matched for transplant function and enalapril dosage immunosuppressed with cyclosporine and prednisone. AZA metabolites did not differ significantly in the presence or absence of the ACEI. Enalaprilat levels also showed no significant difference between the two patient groups treated with AZA or cyclosporine. Hematocrit and hemoglobin increased significantly from 37.5 +/- 6.4 to 39.7 +/- 3.6% (mean +/- SD, P = 0.02) and 12.8 +/- 2.2 to 13.5 +/- 1.2 g/dl, P = 0.04, respectively, 10 to 12 weeks after ACEI treatment had been discontinued. Simultaneously numbers of reticulocytes and erythropoietin concentrations rose significantly after 2, 4 and 10 weeks, with a peak at two weeks (from 14.1 +/- 3.8 to 20.6 +/- 8.0/1000, P < 0.05 and from 14.3 +/- 12.4 to 29.3 +/- 54.5 mU/ml, P < 0.05, respectively). In conclusion, ACEI-related anemia in renal transplant recipients seems to be due to the erythropoietin-lowering effect of this group of drugs. A pharmacokinetic interaction between AZA and enalapril is not likely since plasma enalaprilat levels were independent of the immunosuppressive regimen and AZA metabolite levels were unchanged in the presence and absence of the ACEI. Several mechanisms by which angiotensin converting enzyme blockade may cause a decrease in circulating erythropoietin are discussed.

Enalapril treatment of posttransplant erythrocytosis: efficacy independent of circulating erythropoietin levels

To determine the mechanism of action by which angiotensin-converting enzyme (ACE) inhibitors lower hematocrit in patients with posttransplant erythrocytosis, indices of red blood cell production and red blood cell destruction were obtained serially for 6 months from 10 renal transplant patients receiving treatment with enalapril for this problem. Before treatment, five patients had an elevated red blood cell mass, four had plasma volume contraction, and one had both. The mean hemoglobin concentration decreased by 2 g/dL (range, 0.5 to 3.3 g/dL), from 17 +/- 1 g/dL to 15 +/- 1 g/dL (P = 0.001) following 6 months of enalapril therapy. Similarly, the mean hematocrit decreased by 8% (range, 3% to 12%), from 52% +/- 2% to 44% +/- 3% (P = 0.001) during the same period. The mean reticulocyte count tended to decrease, although the change was not significant. The red blood cell mass decreased dramatically by 15% to 50%, from 32 +/- 9 mL/kl to 23 +/- 4 mL/kg (P = 0.008). Although serial erythropoietin levels declined steadily in two patients, there was no consistent change in the other patients. Mean levels decreased modestly, from 20 +/- 11 mU/mL at baseline to 12 +/- 5 mU/mL at 6 months, a change that was not statistically significant. Mean levels at each time point were not statistically different from the mean pretreatment value. Furthermore, during enalapril therapy, there was no correlation between mean circulating erythropoietin level and mean hematocrit (r = 0.43, P = 0.20) or hemoglobin concentration (r = 0.36, P = 0.30) or between changes in these parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

An early effect of acute plasma volume expansion in humans on serum erythropoietin concentration

The effect of acute plasma volume change in humans on serum erythropoietin [EPO]s, plasma active renin [REN] and plasma aldosterone [ALDO] concentrations was examined. Plasma volume (PV) expansion was induced by intravenous infusion of 150 ml (30g) of plasma albumin and 500 ml of physiological saline. The [EPO]s decreased by 14.3% (corrected values for PV expansion) and remained decreased for 5 h. The [REN] was decreased by more than 25% during the day of the experiment and [ALDO] by more than 60%. Only a weak positive correlation was found between [EPO]s and [REN] (r = 0.35; P < 0.05) but a lack of correlation between changes in PV and [EPO]s as well as between [EPO]s and [ALDO] was seen. We postulated that in healthy men an acute PV expansion by 10% to 17.5% would not appear to promote stimulation of EPO synthesis for at least 11 h. Since a weak positive correlation was observed between [EPO]s and [REN] and a lack of correlation between [EPO]s and [ALDO], it would seem that there is no direct link between [REN] and [ALDO] and erythropoietin synthesis in healthy subjects.

Erythropoiesis after withdrawal of enalapril in post-transplant erythrocytosis

Enalapril effectively decreases hematocrits in patients with postrenal transplant erythrocytosis (PTE). We studied the effect of enalapril withdrawal on erythropoiesis in 18 patients with PTE who had been treated for 13 +/- 8 months. Hematocrit, reticulocyte count, plasma erythropoietin, and plasma insulin-like growth factor I were measured biweekly for six weeks. Red cell mass, plasma volume, transferrin saturation, and plasma angiotensin II were measured at withdrawal and six weeks later. Hematocrit increased by at least 0.04 in 13 patients ('responders') but changed by -0.08 to 0.01 in five patients ('nonresponders'). In the responder subgroup, hematocrit increased from 0.43 +/- 0.05 to 0.51 +/- 0.05 (P < 0.001), red cell mass increased from 25.4 +/- 5.9 to 28.9 +/- 5.9 ml/kg body weight (P < 0.001), and transferrin saturation decreased from 41 +/- 16 to 27 +/- 9 percent (P < 0.01). Reticulocyte count increased two weeks after withdrawal of enalapril. Plasma volume did not change significantly. No measurement changed in the nonresponder subgroup. Plasma levels of erythropoietin, total erythroid stimulating activity, insulin-like growth factor I, and angiotensin II did not change significantly in either subgroup. Enalaprilat did not inhibit erythropoiesis in cell culture. Thus, erythropoiesis increased in 13 of 18 patients after stopping enalapril and was independent of changes in circulating concentrations of several erythropoietic factors, including erythropoietin. The pathogenesis of PTE and mechanism underlying the beneficial effect of angiotensin converting enzyme inhibition remain undetermined.

Captopril and atenolol are equally effective in retarding progression of diabetic nephropathy. Results of a 2-year prospective, randomized study

The progression of diabetic nephropathy can be positively influenced by maintaining a low blood pressure level. This has been shown in studies with conventional antihypertensive treatment as well as with ACE inhibitors. Whether the latter group of drugs is more effective remains to be proven and was the aim of our study. In a prospective randomized study we compared the effects of ACE inhibition and beta-blockade on retarding progression of renal function in IDDM patients with an early stage of overt diabetic nephropathy. Twenty-nine patients were studied for 2 years, 15 were randomized for treatment with captopril and 14 for atenolol. Every 6 weeks blood pressure and urinary albumin and total protein excretion were measured. GFR was measured every 6 months as 51Cr-EDTA clearance. Baseline values for blood pressure, renal function and albuminuria were identical in the two groups. The effect of both drugs on blood pressure was not significantly different. In the captopril-treated patients MAP before and after 2 years was 110 +/- 3 (SEM) and 100 +/- 2 mm Hg, respectively and in the atenolol-treated patients 105 +/- 2 vs 101 +/- 2 mm Hg. Both drugs reduced albuminuria and total proteinuria to the same extent. With captopril albuminuria decreased from 1549 (989-2399) to 851 (537-1380) mg/24 h and proteinuria from 2.5 (1.6-3.8) to 1.2 (0.8-1.8) g/24 h. With atenolol albuminuria decreased from 933 (603-1445) to 676 (437-1047) mg/24 h and proteinuria from 1.5 (1.0-2.4) to 0.9 (0.6-1.5) g/24 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Postrenal transplant erythrocytosis: further evidence implicating erythropoietin production by the native kidneys

True erythrocytosis is a relatively common complication of successful renal transplantation. From a group of 17 patients with post-transplant erythrocytosis (PTE), four underwent selective venous catheterization of the native and transplanted kidneys because of arterial hypertension. In three who presented with active PTE at the time the procedure was performed the peripheral blood (PB) concentration of EPO was elevated, and the level of erythropoietin (EPO) in native kidney veins was significantly higher than the PB and allograft EPO levels. Additionally, only one of the three cases had high levels of plasma renin activity (PRA). The fourth patient showed normal levels of EPO and PRA in PB and in venous blood from the native and transplanted kidneys. However, the PTE had subsided 4 months before the performance of the catheterization after he redeveloped terminal renal failure; the loss of a functioning allograft might have blunted the overproduction of EPO by the native kidneys. In conclusion, in patients with PTE, inappropriate EPO production seems to originate from the diseased native kidneys, and there seems to be no correlation between the production of EPO and the PRA.

Effect of captopril on the renal veno-arterial gradient of erythropoietin and oxygen in unilateral renal artery disease

Twenty-nine patients with unilateral renal artery stenosis or occlusion were investigated. The veno-arterial gradient (VA-gradient) of erythropoietin (EPO), haemoglobin oxygen saturation and plasma renin activity (PRA) was determined separately in each kidney before and 1 h after angiotensin converting enzyme inhibition (ACE-inhibition). The VA-gradient of EPO and of hemoglobin oxygen saturation were the same in the affected and unaffected kidney during basal conditions. During ACE-inhibition the VA-gradient of EPO disappeared on the affected side but not on the unaffected side. A fall in s-EPO after ACE inhibition was demonstrated in the renal vein on the affected side (-1.4 U l-1, p < 0.01), in the contralateral vein (-0.8 U l-1, p < 0.01) and in the aorta (-0.6 U l-1, p < 0.01). The O2-gradients were reduced on both sides after captopril, from 10.8-7.5% (p < 0.04) on the affected side and from 10.8-9.0% (p < 0.04) on the contralateral. It is suggested that the stimulated renin-angiotensin system may be important for EPO production in the affected kidney in unilateral renal disease.

What effect does blood pressure control have on the progression toward renal failure?

Since hypertension is associated with nephrosclerosis and an increased progression toward end-stage renal failure, the therapeutic approach to the treatment of hypertension should aim to protect the kidney against damage or to halt the progression toward end-stage renal failure. It appears that compared with systolic and mean blood pressure, the level of diastolic blood pressure is particularly associated with renal damage. In the presence of kidney failure the choice of antihypertensive drug should be made according to pharmacokinetic and pharmacodynamic properties. From the pharmacokinetic point of view, drugs that are eliminated via the biliary route are preferable since no dosage adjustment is required, and those with a favorable trough to peak effect can achieve better blood pressure control by reducing blood pressure variability. Pharmacodynamic properties should include efficacy in lowering blood pressure, beneficial renal effects, and good tolerability. Hence, the dihydropyridine calcium antagonists, which are effective during volume repletion and which counteract vasoconstrictor mechanisms, seem to be particularly effective. There is some suggestion, but no definitive proof, that blood pressure should be lowered well below 140/90 mm Hg; to achieve this, combination therapy frequently must be used. The rationale for combining two or more antihypertensive drugs is based on the knowledge that this combination can exert an additive antihypertensive action while reducing side effects. The combination of an angiotensin converting enzyme inhibitor with a dihydropyridine calcium antagonist may well fulfill these criteria since this combination could enhance both antihypertensive and renal hemodynamic effects in comparison to single-drug treatment and could reduce the side effects of both drugs.

Elevated level of erythropoietin in congestive heart failure relationship to renal perfusion and plasma renin

BACKGROUND

In animal experiments reduction of renal perfusion can stimulate erythropoietin production. The relationship between renal haemodynamics and erythropoietin production is unknown in congestive heart failure.

OBJECTIVE

The aim was to study the relationship between serum erythropoietin and renal haemodynamics, plasma renin activity and haematocrit in patients with congestive heart failure and in healthy control subjects.

PATIENTS AND METHODS

Serum erythropoietin, renal plasma flow, glomerular filtration rate and plasma renin activity were determined in 14 patients with acyanotic congestive heart failure, and 36 healthy controls.

RESULTS

Serum erythropoietin was significantly elevated in congestive heart failure 26.6 U l-1 (median) compared with controls 17.0 U l-1 despite a normal haematocrit, and increased with the severity of congestive heart failure (New York Heart Association class II: 17 U l-1 [n = 4]; class III: 30 U l-1 [n = 5]; class IV: 45 U l-1 [n = 5]). Significant inverse correlations between serum erythropoietin and renal plasma flow (r = -0.60, P < 0.03), and between serum erythropoietin and glomerular filtration rate, were found in congestive heart failure but not in the control subjects. A significant positive correlation (r = 0.71, P < 0.03) was demonstrated between serum erythropoietin and plasma renin activity in congestive heart failure.

CONCLUSION

A severe reduction in renal perfusion in congestive heart failure appears to cause an increase in serum erythropoietin.

Comparison of enalapril and nifedipine in treating non-insulin dependent diabetes associated with hypertension: one year analysis

OBJECTIVES

To compare the efficacy, safety, and tolerance of enalapril and nifedipine in hypertensive patients with non-insulin dependent diabetes.

DESIGN

One year double blind follow up of patients randomly allocated to either enalapril or nifedipine with matching placebos for the alternative drug.

SETTING

Metabolic Investigation Unit, Hong Kong.

SUBJECTS

102 patients were randomised: 52 to nifedipine and 50 to enalapril. At baseline 44 patients had normoalbuminuria, 36 microalbuminuria, and 22 macroalbuminuria.

MAIN OUTCOME MEASURES

Blood pressure, albuminuria, and parameters of renal function and glycaemic control.

RESULTS

In patients who completed one year's treatment the median dose required by the nifedipine group (n = 49) was 60 mg/day; seven (14%) required additional diuretics. Of 41 patients given enalapril, 37 required the maximum dose (40 mg/day) and 27 (76%) required diuretics. At one year mean arterial blood pressures were similar in both groups. Albuminuria fell by 54% in the enalapril group and 11% in the nifedipine group (p = 0.006). Fractional albumin clearance ratio fell by 47% in the enalapril group and increased by 3% in the nifedipine group (p = 0.009). Creatinine clearance fell similarly in both groups but plasma creatinine concentration was increased by 20% in the enalapril group versus 8% in the nifedipine group (p = 0.001).

CONCLUSION

Patients taking enalapril often required diuretics to control blood pressure. Enalapril reduced proteinuria significantly more than nifedipine in the microalbuminuric and macroalbuminuric patients but increased plasma creatinine concentrations. Longer follow up is required to clarify the importance of enalapril's antiproteinuric effect.

Effect of angiotensin converting enzyme inhibitors on erythropoietin concentrations in healthy volunteers

The possibility that the ACE inhibitors, enalapril and captopril, may decrease plasma EPO concentrations was studied in a single-blind, cross-over study in 10 healthy volunteers. Plasma EPO concentrations, haemoglobin concentration, red blood cell count, plasma creatinine concentration and mean arterial pressure were measured at baseline and after 28 days treatment with both ACE inhibitors. A significant fall in mean plasma EPO concentration occurred with both ACE inhibitors and returned to baseline after stopping the drugs. It is likely that ACE inhibitors decrease EPO formation, by inhibition of angiotensin-II production. This effect could be important in patients with renal failure, renal transplantation or other chronic conditions with an associated anaemia. Haematological parameters should be monitored in such patients when they are treated with an ACE inhibitor.

Enalapril. A reappraisal of its pharmacology and therapeutic use in hypertension

Enalapril, an angiotensin converting enzyme (ACE) inhibitor usually administered orally once daily, decreases blood pressure by lowering peripheral vascular resistance without increasing heart rate or output. It is effective in lowering blood pressure in all grades of essential and renovascular hypertension. Patients not responding adequately to enalapril monotherapy usually respond with the addition of a thiazide diuretic (or a calcium antagonist or beta-blocker), and rarely require a third antihypertensive agent. Enalapril is at least as effective as other established and newer ACE inhibitors, and members of other antihypertensive drug classes including diuretics, beta-blockers, calcium antagonists and alpha-blockers, but therapy with enalapril may be less frequently limited by serious adverse effects or treatment contraindications than with other drug classes. The most frequent adverse effect limiting all ACE inhibitor therapy in clinical practice is cough. This favourable profile of efficacy and tolerability, and the substantial weight of clinical experience, explain the increasing acceptance of enalapril as a major antihypertensive treatment and supports its use as logical first-line therapeutic option.

Enalapril-induced anemia in two kidney transplant recipients

Two renal transplant patients developed anemia during treatment of hypertension with enalapril medication. Hemoglobin levels normalized after administration of enalapril was stopped. In one patient, it was demonstrated that the discontinuation of enalapril was followed by a decrease in renal blood flow and a significant increase in the plasma erythropoietin levels that preceded the rise in hemoglobin. These observations are consistent with the hypothesis that angiotensin-converting enzyme inhibition may cause anemia by increasing renal blood flow and consequently decreasing erythropoietin levels.

Renal protective effect of enalapril in diabetic nephropathy

OBJECTIVE

To determine whether inhibition of angiotensin converting enzyme can reduce the rate of decline in kidney function more than reducing blood pressure with other antihypertensive treatment.

DESIGN

Prospective, open randomised study lasting a mean of 2.2 years in patients with diabetic nephropathy.

SETTING

Three outpatient nephrology clinics.

PATIENTS

40 patients with insulin dependent diabetes and diabetic nephropathy with reduced renal function.

INTERVENTION

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

MAIN OUTCOME MEASURE

Rate of decline in glomerular filtration rate measured as chromium-51 edetic acid clearance.

RESULTS

Glomerular filtration rate declined a mean of 2.0 (SD 3.2) ml/min/year in the group given enalapril and 5.6 (5.9) ml/min/year in the control group. The mean arterial blood pressure during the study was 102 (5) mm Hg in the patients given enalapril and 103 (5) mm Hg in the patients given metoprolol. Urinary albumin excretion during treatment with enalapril was 60% lower than during treatment with metoprolol.

CONCLUSIONS

Enalapril has an antiproteinuric effect independent of the effect on systemic blood pressure. Treatment with enalapril can reduce the rate of decline in kidney function in patients with diabetic nephropathy more than equally effective antihypertensive treatment with metoprolol. This points to a specific renal protective effect of angiotensin converting enzyme inhibitors in diabetic nephropathy.