Urinary diluting capacity in elderly diabetic subjects.
Urinary concentrating ability declines with normal human aging but diluting capacity has been less well studied as a function of age. We studied free water clearance (CH2O) in a group of Type II diabetic patients, aged 47 to 70 years. Conventional water load testing in sulfonylurea-treated diabetic patients revealed preservation of diluting capacity (ability to achieve Uosm less than 100 mOsm/kg) in subjects greater than 60 years of age. Tolazamide permitted expression of normal CH2O; chlorpropamide administration predictably reduced CH2O relative to tolazamide by 58% in subjects greater than 60 years. Free water clearance (CH2O) and glomerular filtration rate (GFR) were comparable in elderly subjects (greater than 60 years) and those less than or equal to 60 years. Normal CH2O in these diabetic patients was explained by persistently normal GFR in the study group. Osmolar clearance (Cosm) was insignificantly lower in diabetics greater than 60 years. Thus, a fall in CH2O in elderly diabetic patients is not a factor contributing to clinical hypoosmolar states encountered in this population.
D000368:Aged; D000375:Aging / Q000378:metabolism*; D002747:Chlorpropamide / Q000008:administration & dosage; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D003928:Diabetic Nephropathies / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006801:Humans; D007671:Kidney Concentrating Ability / Q000187:drug effects; D008297:Male; D008875:Middle Aged; D013453:Sulfonylurea Compounds / Q000008:administration & dosage; D014042:Tolazamide / Q000008:administration & dosage; D014867:Water / Q000008:administration & dosage; D014882:Water-Electrolyte Balance
D013453:Sulfonylurea Compounds; D014867:Water; D014042:Tolazamide; D002747:Chlorpropamide