Calcium channel blockers and albuminuria in hypertensive diabetic subjects: A pilot study

Diltiazem tends to decrease proteinuria in hypertensive diabetic subjects i n comparison to amlodipine that does not modify it. Since estimated glomeru lar pressure is identical in amlodipine treated and diltiazem treated subje cts, differences in albuminuria may be explained by different renal tubular reabsorption rates. Objectives: 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 o f albumin-Tc99m. Test the hypothesis that amlodipine decreases renal tubula r reabsorption of albumin in diabetic hypertensive subjects. Methods: Fourteen diabetic and hypertensive subjects (DH) (average plasma c reatinine: 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 (S subjects). Their glomerular filtration, glomer ular pressure and albumin-Tc99m PC were then assessed on the 3rd. 6th, and 12th month of the study. Results: Albumin-Tc99m PC obtained from serial blood draws: A decrease in P C between months 0 and 3 from 14 to 10,6 cc/min was observed in subjects tr eated with amlodipine but subjects on diltiazem showed PC stability (from 1 1.9 to 12 cm(3)/min). PC obtained from urinary excretion: Amlodipine and di ltiazem treated subjects showed PC stability. Plasma volume in amlodipine t reated subjects decreased from 156 to 127% and diltiazem treated subjects f rom 128 to 117%. Conclusion: A decrease in PC obtained with plasma measurements and stabilit y of PC based on urinary excretion measurements tends to identify a decreas e in plasma volume. A decrease in albumin-Tc99m tubular reabsorption was no t observed. The estimate of albumin PC with Tc 99m labelled albumin measure ments still needs to be validated.