URINARY-EXCRETION OF TAMM-HORSFALL PROTEIN IN NORMOTENSIVE, NORMO-ALBUMINURIC TYPE-1 DIABETIC-PATIENTS

The excretion rate of a marker of distal tubular function, Tamm-Horsfa ll protein (THP), has been measured in urine (mu g/min) overnight, dur ing orthostasis and during a glycaemic clamp (blood glucose concentrat ion 7.0 mmol/l) with stable diuresis in 41 normotensive, normo-albumin uric type 1 diabetic patients. Eleven healthy subjects who were not cl amped served as controls. A further 4 normo-albuminuric type 1 diabeti c patients were rendered euglycaemic without a waterload. The excretio n rate of THP overnight was similar in type 1 diabetic patients and no rmal subjects (26.1 vs. 23.5 mu g/ml, p = NS). During the waterloaded euglycaemic clamp, THP increased significantly both in type 1 diabetic patients and control subjects (p < 0.001), but the increase was sligh tly greater in type 1 diabetic patients (67.2 vs. 38.4 mu g/min, p = 0 .05). Orthostasis did not increase the excretion rate of THP in either type 1 diabetic patients or in control subjects. In the 4 type 1 diab etic patients who were only clamped, the THP excretion rate increased less compared to the clamp plus waterload experiment (means: overnight 11.3 mu g/min; clamp 22.5 mu g/min). In Type 1 diabetes, overnight TH P excretion was inversely correlated both with fasting blood glucose, HbA1 and sodium-lithium counter-transport activity (SLC). A direct rel ationship was present between urinary flow and the excretion rate of T HP. In conclusion, this study shows that normotensive, normoalbuminuri c type 1 diabetic patients present similar overnight excretion rates o f THP compared to healthy controls and that the excretion rate of THP is unaffected by posture and increased during acute euglycaemia and wa terload. The association between SLC and THP might suggest some relati on between this putative marker of nephropathy and distal tubular func tion, but this finding needs confirmation and further study.