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  • 1
    ISSN: 1432-0428
    Keywords: Autoregulation ; arterial blood pressure ; glomerular filtration ; diabetic nephropathy ; Type 1 diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of acute lowering of arterial blood pressure upon kidney function in nephropathy was studied in 13 patients with long-term Type 1 (insulin-dependent) diabetes. Ten normal subjects (six normotensive and four hypertensive) and five short-term Type 1 diabetic patients without nephropathy served as controls. Renal function was assessed by glomerular filtration rate (single bolus 51Cr-EDTA technique) and urinary albumin excretion rate (radial immunodiffusion). The study was performed twice within 2 weeks, with the subjects receiving an intravenous injection of either clonidine (225 μg) or saline (0.154 mmol/l). The arterial blood pressure was similar in the diabetic patients with nephropathy (mean 136±11 mmHg) and in the non-diabetic control subjects 88±5 (mean 140±25 mmHg). The clonidine injection induced sim- 92±15 ilar reductions in mean arterial blood pressure in all three groups (16–18 mmHg). While glomerular filtration rate and urinary albumin excretion rate remained unchanged in both control groups after clonidine injection, glomerular filtration rate dimished from 78 to 71 ml/min per 1.73 m2 (p〈0.01), and urinary albumin excretion declined from 1707 to 938 μg/min (p〈0.01) in the patients with diabetic nephropathy. Our results suggest that an intrinsic vascular (arteriolar) mechanism underlying the normal autoregulation of glomerular filtration rate, i. e. the relative constancy of glomerular filtration rate that occurs in response to rather wide variations in perfusion pressure, is defective in diabetic nephropathy.
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  • 2
    ISSN: 1432-0428
    Keywords: Autoregulation ; arterial blood pressure ; glomerular filtration ; incipient diabetic nephropathy ; Type 1 diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of an acute reduction in arterial blood pressure upon kidney function was studied in 12 patients with Type 1 (insulin-dependent) diabetes and incipient nephropathy (persistent microalbuminuria). Renal function was assessed by measurement of the glomerular filtration rate (single bolus 51Cr-EDTA technique) and by the urinary albumin excretion rate (radioimmunoassay). The study was performed twice within 2 weeks, with the patients receiving a slow intravenous injection of either clonidine (225 μg) or saline (154 mmol/l) in random order. Clonidine reduced arterial blood pressure from 125/79±13/8 to 104/68±9/7 mmHg (p 〈 0.01), urinary albumin excretion rate from 68 (31–369) to 46 (6–200) μg/min (median and range) (p〈0.01), and fractional clearance of albumin in all patients (median 29%) (p 〈 0.01). Glomerular filtration rate was 110±11 before and 106±13 ml/min/1.73 m2 after clonidine injection. The blood glucose concentration was 15±4mmol/l before and 14±5 mmol/l after clonidine injection. In agreement with findings in animal studies, our results suggest that microalbuminuria is to a large extent pressure-dependent, probably because of glomerular hypertension, and that autoregulation of glomerular filtration rate is normal in most patients with incipient diabetic nephropathy.
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  • 3
    ISSN: 1432-0428
    Keywords: Albuminuria ; arterial blood pressure ; glomerular filtration ; diabetic nephropathy ; microvascular permeability ; transport kinetics ; Type 1 diabetes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of acute arterial blood pressure lowering upon albumin extravasation was studied in 10 patients with nephropathy and retinopathy due to long-standing Type 1 (insulin-dependent) diabetes. The following variables were measured: transcapillary escape rate of albumin (initial disappearance of intravenously injected 125I-labelled human serum albumin), and urinary albumin excretion rate (radial immuno-diffusion). The study was performed twice within 2 weeks, with the patients receiving an intravenous injection of either clonidine (225 μg) or saline (0.154 mmol/l). The clonidine injection induced the following changes: arterial blood pressure decreased from 134/87 to 107/73 mmHg (p〈0.01), transcapillary escape rate of albumin declined from 8.1 to 6.7% of the intravascular mass of albumin/h (p〈0.01), albuminuria diminished from 1434 to 815 μg/min (p〈0.01), and plasma volume raised slightly from 2916 to 2995ml (p〈0.05). Our findings demonstrate that the enhanced albumin passage through the wall of the microvasculature characteristically found in long-term Type 1 diabetic patients with clinical microangiopathy is pressure-dependent to a large extent. This may be due to elevated hydrostatic pressure in the microcirculation.
    Type of Medium: Electronic Resource
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