Kinetics of sodium-lithium countertransport activity in patients with uncomplicated type 1 diabetes.
1. Increased erythrocyte sodium-lithium countertransport activity has been reported to be associated with nephropathy in type 1 diabetes and linked to a family history of essential hypertension. 2. This study aimed to determine the mechanism of increased sodium-lithium countertransport activity. Sodium-lithium countertransport kinetics were measured in uncomplicated and hyperlipidaemic type 1 diabetic patients. 3. In the nine out of 31 uncomplicated type 1 diabetic patients who had high sodium-lithium countertransport activity, the sodium affinity (Km) was normal but the maximum velocity (Vmax) was increased. 4. Hyperlipidaemia, when present in diabetic patients, was associated with increased sodium-lithium countertransport activity, but could not explain the high activity in uncomplicated type 1 diabetic patients in whom plasma lipid concentrations were normal. 5. Sodium-lithium countertransport activity is increased in type 1 diabetes by a mechanism different to that in essential hypertension, where the mechanism is a low Km (increased sodium affinity). Hence familial hypertension cannot explain the raised sodium-lithium countertransport activity in type 1 diabetes.
Rutherford
P A
PA
Department of Medicine (Nephrology), Freeman Hospital, University of Newcastle-upon-Tyne, U.K.
Thomas
T H
TH
Carr
S J
SJ
Taylor
R
R
Wilkinson
R
R
D000328:Adult; D017920:Antiporters; D002352:Carrier Proteins / Q000378:metabolism*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D004912:Erythrocytes / Q000378:metabolism; D005260:Female; D006400:Hematocrit; D006801:Humans; D007700:Kinetics; D008297:Male; D013997:Time Factors
D017920:Antiporters; D002352:Carrier Proteins; C045885:sodium-lithium countertransporter