Arterial hypertension and proteinuric nephropathy are common features in diabetic patients. In streptozotocin-diabetic rats, it has been possible to reduce the blood pressure and proteinuria by converting enzyme inhibitors, and so slowing the decline of kidney function. These results have been confirmed in diabetic patients affected by arterial hypertension and persistent proteinuria. However, up to now it has not been clear if these favorable renal effects are related specifically to converting enzyme inhibition. In the attempt to clarify this last point, from a practical as well as from a speculative point of view, 12 type 2 diabetic outpatients affected by mild to moderate arterial hypertension and persistent macroalbuminuria (greater than 250 mg/daily, at least on three consecutive occasions) without any other signs of renal diseases were studied. In a randomized sequence and in a double blind fashion, after a washout period of 3 weeks, the patients underwent pharmacological treatment which consisted of enalapril 20 mg o.d., chlorthalidone 12.5 mg o.d., atenolol 50 mg o.d. and placebo o.d. Each treatment lasted 45 days. Kidney function, blood pressure and heart rate were checked at the beginning and at the end of each treatment, while urinary albumin excretion was measured at the end of the 4th, 5th, and 6th week of each treatment. Blood pressure significantly decreased in a similar fashion after each active treatment, while kidney function did not change significantly. Urinary albumin excretion rate significantly decreased after enalapril and atenolol, but did not change after chlorthalidone. According to these results we can hypothesize that the inhibition of tissue angiotensin formation and its related change on the glomerular permeability, rather than renal and systemic hemodynamic features, seem to be the common mechanisms by which both enalapril as well as atenolol decrease the albuminuria in our patients.
Centro per lo Studio e la Terapia dell'Ipertensione, Ospedale Generale Umberto I, Siracusa, Italy.