Background: It is known that hypertension to aggravate the course of chronic renal insufficiency (CRI). It is too know the beneficial effect of the angiotensin-converting enzyme inhibitors (ACEI) and the low-protein diet. In this study, the effect of a low protein diet on the course of CRI was compared with that of administration of enalapril (ENA), an ACEI.
Methods and results: A new model of genetic hypertension, the Prague Hypertensive Rat (PHR) was used. In rats just after weaning, 5/6 of renal parenchyma were removed surgically (5/6NX). The rats were observed for 8 weeks after 5/6NX. The animals were fed either a normal rat chow containing 23% of protein, or a low-protein diet containing only 6% protein. Control groups drank tap water, experimental groups received water containing ENA at a dose of 5 mg/kg BW. The rats on normal diet drinking water had the highest levels of blood pressure (200 +/- 4.3 mm Hg), proteinuria (56.2 +/- 14.6 mg/24 hours) and heaviest kidney remnants i.e. highest compensatory hypertrophy (2352 +/- 239.4 mg). Both ENA and low-protein diet significantly improved these functions to the same extent. However, a combination of low-protein diet with ENA had no further beneficial effect as against any of these manoeuvres alone.
Conclusions: We assume every manoeuvre (low-protein diet and enalapril) exerts a maximal beneficial effect per se: the mechanism of this effect is highly speculative: inhibition of growth factors seems to be the most logical explanation. ACEIs are known to inhibit the production of angiotensin II, low-protein diet should inhibit transforming growth factor beta.