RED-CELL SODIUM-LITHIUM COUNTERTRANSPORT AND BLOOD-PRESSURE IN CHILDREN WITH INSULIN-DEPENDENT DIABETES-MELLITUS

Sodium-lithium countertransport and blood pressure responses, maximal elevated plasma norepinephrine concentrations induced by acute physica l work load and the carbohydrate metabolic state were analyzed in 40 c hildren suffering from insulin-dependent diabetes mellitus (IDDM). Pat ients were selected according to the duration of the disease to get a horizontal insight into the progression of the diabetes, Sixteen healt hy children served as controls. Sodium-lithium countertransport (Na-Li CT) was 281 +/- 64 mu mol/l red blood cells (RBC) per hour in the con trol group, Na-Li CT was elevated in all diabetic groups (newly diagno sed: 455 +/- 48; diabetics for 5-7 years: 495 +/- 48; diabetics for 10 -13 years: 470 +/- 36). Plasma norepinephrine concentration increased during physical exercise, the elevation was more pronounced in diabeti c children being 13.5 +/- 10.4, 10.1 +/- 5.0 and 12.3 +/- 5.4 nmol/l i n the three diabetic groups, respectively, which differed significantl y from that of controls (7.94 +/- 2.9; P < 0.01). Systolic blood press ure increased significantly during physical exercise in each group. Ho wever, maximal elevated systolic blood pressure was higher in children who had diabetes for more than 10 years than in controls (158 +/- 11 vs, 137 +/- 9.7 mmHg; P < 0.001). Na-Li CT correlated positively with the maximal systolic blood pressure measured during physical exercise in those diabetic children who suffered from diabetes for more than 5 years. High activity of Na-Li CT in combination with elevated blood pr essure and high plasma concentration of norepinephrine induced by acut e physical exercise may represent a risk of renal/vascular complicatio ns in patients suffering from IDDM.