The relationship of urinary albumin excretion rate to ambulatory blood pressure and erythrocyte sodium-lithium countertransport in NIDDM

Summary Increased erythrocyte sodium-lithium countertransport rate is found in non-diabetic subjects with essential hypertension, and in insulin-dependent diabetic subjects with nephropathy. However, relationships between these variables in non-insulin-dependent diabetic subjects are ill-defined. In order to characterise the relationships between blood pressure, urinary albumin excretion, and erythrocyte sodium-lithium countertransport, 66 subjects with non-insulin-dependent diabetes were studied. Urinary albumin excretion rate correlated with mean 24-h ambulatory systolic blood pressure (r=0.57; p<0.001), but not with sodium-lithium countertransport (r=0.06; p=0.31). No significant relationship was observed between 24-h systolic blood pressure and erythrocyte sodium-lithium countertransport (r = 0.16; p=0.17). The principal differences between microalbuminuric and normoalbuminuric subjects (albumin excretion rate >15 g·min^–1 [n=20], and <15 g·min^–1, [n=46]) were: higher 24-h systolic blood pressure (145.9 [16.8] mm Hg vs 131.9 [16.8] mm Hg; p=0.006), nocturnal heart rate (72.4 [8.9] vs 67.4 [8.9] beats·min^–1; p=0.042), and HbA₁ (11.3 [1.5]% vs 10.1 [2.0]%; p=0.028), and a longer median duration of diabetes (10.0 vs 5.0 years; p = 0.02). In contrast, there was no significant difference in sodium-lithium countertransport rate between microalbuminuric (0.41 [0.18] mmol·l^–1·h^–1) and normoalbuminuric subjects (0.39 [0.15] mmol·l^–1· h^–1; p=0.687). In multiple regression analysis controlling for race, age, body mass index and HbA₁, the significant determinants of albumin excretion rate were 24-h systolic blood pressure (B [regression coefficient]=0.029, SE[B] [standard error of B]=0.009, t=2.95, p=0.005), duration of diabetes (B=0.430, SE[B]=0.169, t=2.54, p=0.016) and male gender (B=–1.170, SE[B]=0.457, t=–2.56, p=0.015). In conclusion, albumin excretion rates in non-insulin-dependent diabetic subjects are linked to hypertension and glycaemic exposure, but show no relationship to erythrocyte sodium-lithium countertransport.Abbreviations IDDM Insulin-dependent diabetes mellitus - NIDDM non-insulin dependent diabetes mellitus - SLC sodium lithium countertransport - AER albumin excretion rate - B regression - SE coefficient; standard error of B