[Calcium channel blocking agents and albuminuria in diabetic and hypertensive patients. A pilot study]

Diltiazem tends to decrease proteinuria in hypertensive diabetic subjects in comparison to amlodipine that does not modify it. Since estimated glomerular pressure is identical in amlodipine treated and diltiazem treated subjects, differences in albuminuria may be explained by different renal tubular reabsorption rates.

To compare plasma clearances (PC) of technetium labeled albumin (albumin-Tc99m) obtained by serial plasma measurements with PC obtained by urinary excretion measurements. Indirectly evaluate tubular reabsorption of albumin-Tc99m. Test the hypothesis that amlodipine decreases renal tubular reabsorption of albumin in diabetic hypertensive subjects.

Fourteen diabetic and hypertensive subjects (DH) (average plasma creatinine: 94 mmol/L) and 6 normal subjects (average plasma creatinine: 82 mmol/L) had previously been assessed for albumin-Tc99m PC. Eleven of these 14 DH subjects were then randomized to diltiazem 300 mg/daily (6 subjects) or amlodipine 10 mg/daily (5 subjects). Their glomerular filtration, glomerular pressure and albumin-Tc99m PC were then assessed on the 3rd, 6th, and 12th month of the study.

Albumin-Tc99m PC obtained from serial blood draws: A decrease in PC between months 0 and 3 from 14 to 10.6 cc/min was observed in subjects treated with amlodipine but subjects on diltiazem showed PC stability (from 11.9 to 12 cm3/min). PC obtained from urinary excretion: Amlodipine and diltiazem treated subjects showed PC stability. Plasma volume in amlodipine treated subjects decreased from 156 to 127% and diltiazem treated subjects from 128 to 117%.

A decrease in PC obtained with plasma measurements and stability of PC based on urinary excretion measurements tends to identify a decrease in plasma volume. A decrease in albumin-Tc99m tubular reabsorption was not observed. The estimate of albumin PC with Tc 99m labelled albumin measurements still needs to be validated.