Blood pressure changes and renal function in incipient and overt diabetic nephropathy.

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Abstract
Four studies are included in this report on the relationship of blood pressure, protein excretion, and renal hemodynamics, where renal function was measured by 125I-iothalamate clearance and 131I-hippuran clearance, and urinary albumin excretion was measured by radioimmunoassay. The first concerns the relationship between blood pressure and renal function in a cross-sectional study of 56 patients with type I diabetes with various degrees of renal involvement. In the second, multiple regression analysis was used in a prospective study of diabetic nephropathy in patients with type I diabetes. Inclusion criteria were age at diagnosis less than 20 years, initial diabetes duration 3 to 20 years, and follow-up period more than 7 years. Urinary albumin was less than 70 micrograms/min, and glomerular filtration rate, renal plasma flow, and urinary albumin were measured in all patients. The third was a long-term follow-up study of persons with type I diabetes, with special reference to development of changes in urinary albumin, glomerular filtration rate, and blood pressure. Diabetes duration in this study was 7 to 20 years. Finally, a prospective study was conducted on clinical proteinuria and mortality in patients with type II diabetes, with special reference to initial urinary albumin and blood pressure. A close association was established among all variables measured in the cross-sectional study. On multiple regression analysis as well as in the long-term follow-up study, it appeared that both elevated urinary albumin (greater than 15 micrograms/min at baseline) and high glomerular filtration rate (greater than 150 ml/min) are major determinants for subsequent progression to nephropathy. In patients with type II disease, increase in urinary albumin is a strong predictor for development of proteinuria and early mortality. High blood pressure seems not to be a major determinant in these patients, but further studies are required.