Sodium-lithium countertransport in children with diabetes and their families.

Abnormalities of sodium-lithium countertransport have been extensively implicated in adult primary hypertension and a relationship between sodium-lithium countertransport and family history of hypertension in children has been previously found. More recently it has been suggested that increased sodium-lithium countertransport may play a part in the pathogenesis of nephropathy in insulin dependent diabetes mellitus (IDDM). Children and adolescents with IDDM and their family members were studied. In those with IDDM (n = 36, median age 14.6 years, range 9.5-19.2 years) there was no relationship between sodium-lithium countertransport (range 0.098-0.585 mmol/l red blood cells/hour) and age, blood pressure as expressed by systolic or diastolic SD scores, glycated haemoglobin, serum lipids, or intracellular sodium concentration. A positive relationship (rs = 0.44) was found between sodium-lithium countertransport and early morning urinary albumin to urinary creatinine ratio (UA/UC), expressed as the logarithm of the geometric mean of two consecutive samples, for each individual (range 0.4-22 mg/mmol). Sodium-lithium countertransport was increased in those with IDDM compared with their non-diabetic siblings, in a paired analysis (n = 26). There was no relationship between UA/UC in the children with diabetes and sodium-lithium countertransport in their parents. These studies in this population of diabetic children indicate that increased sodium-lithium countertransport may play a part in the early stages of the development of nephropathy in IDDM.