Influence of converting enzyme inhibition on glomerular filtration rate and proteinuria

Abstract

The progression of chronic renal failure is facilitated by the presence of arterial hypertension. Antihypertensive therapy has been shown to effectively protect the kidney from continuous functional derangement [1, 2]. The degree of proteinuria has also been shown to be a prognostic factor for the progression of chronic renal insufficiency [3, 4]. Recently, experimental [5, 6] and preliminary clinical data [7] have shown that converting enzyme inhibitors are effective in slowing the progression of chronic renal failure. These drugs also have the capacity to reduce glomerular proteinuria [8, 9], and through this mechanism they also have the ability to change the rate of progression of chronic renal failure. On the other hand, the measurement of the progression of chronic renal failure remains as a matter of debate [10, 11]. The usefulness of the slopes of the reciprocal of serum creatinine has been questioned [10–12] and there seems to be general agreement in the sense that sequential measurements of isotope glomerular filtration rate or inulin clearance are the most reliable methods to determine the rate of progression of chronic renal failure. This paper contains our experience on long-term effects of the therapy with the angiotensin converting enzyme, captopril, on the glomerular filtration rate and on the rate of progression of renal insufficiency of patients with chronic renal failure and arterial hypertension. Two previous publications of our group [7, 9] contain the initial results of this study obtained during the first year of follow-up in Group 1 and the first six months in Group 2. Before switching their therapy to captopril, patients were divided in two groups: Group 1, patients with primary non-glomerular disease who exhibited a progressive decline in renal function; their blood pressure was adequately controlled by means of standard triple therapy. They were initially classified by the finding of a negative and significant slope of the reciprocal of serum creatinine. Group 2 were patients diagnosed by a renal biopsy as having a primary glomerular disease with chronic renal failure, who presented with an adequate control of their arterial hypertension with one or two standard drugs. The long-term comparison of captopril versus standard therapy on the progression of renal failure and on non-diabetic glomerular proteinuria, as well as an evaluation of the different methods employed to evaluate glomerular filtration rate are presented.