TAMM-HORSFALL-PROTEIN, ALPHA-1, AND BETA- 2-MICROGLOBULIN AS MICROMOLECULAR MARKERS OF RENAL-FUNCTION IN CARDIAC-SURGERY

After cardiac surgery, transient renal dysfunction often occurs. Regio nal differentiation of these processes is possible only using invasive techniques, including renal biopsy. Approximately 30 different plasma protein components have been identified in the urine of healthy indiv iduals by means of qualitative and quantitative immunochemical methods . The detection of microalbuminuria has high diagnostic relevance for the early diagnosis of renal damage at a reversible stage. One typical urinary protein is Tamm-Horsfall protein (THp). After histochemical s taining of human kidney sections, activity is seen in the loop of Henl e and initial distal tubule. The assay of alpha - 1 microglobulin (MG) in urine is considered one of the most efficient laboratory parameter s for the diagnosis of tubular lesions. Serum concentrations of alpha - 1 MG are less dependent on extrarenal changes than are those of othe r low-molecular-weight proteins. beta-2 MG is also one of the standard s used in recent years for diagnostic relevance. Urinary albumin excre tion, normaly less than 30 mg per day, sometimes increases after glome rular damage. Some renal function tests are used daily in many intensi ve care units, e.g. creatinine clearance (CCr) or urea and sodium excr etion. Renal dysfunction should, however, be further examined to local ise regional damage and to seek new clinical standards In addition to the conventional tests. Methods. After obtaining the agreement of the local ethics committee, 30 patients were divided into two groups of 15 each: group I without renal dysfunction and CCr more than 60 ml/min; and group II with CCr below 60 ml/min. THp and alpha - 1 MG were measu red pre- and postoperatively after open heart surgery with the ELISA a nd beta-2 MG with the nephelometric technique. These parameters were c ompared with clinical standards such as albumin excretion, blood urea nitrogen (BUN), urea clearance, and fractional sodium excretion. Resul ts. The CCr did not change in group I from the pre- to postoperative p eriod (81.5 to 85.1 and 91.4 ml/min), nor did excretion of THp (20.1 t o 25.0 and 24.8 mg/day), correlation r = 0.7; P < 0.001). The eliminat ion of alpha - 1 and beta - 2 MG was significantly higher in the posto perative period in this group (alpha - 1: 7.2 to 44.1 and 100.6 mg/day ; beta - 2: 0.3 to 2.1 and 3.2 mg/day). In group II CCr showed patholo gical values (36.8 to 31.1 and 36.3 ml/min), as did simultaneous THp ( 13.5 to 9.7 and 12.7 mg/day). alpha - 1 and beta-2 MG values became mo re pathological in the postoperative period than in group I (alpha - 1 : 32.8 to 113.9 and 198.5 mg/day; beta-2: 0.7 to 5.8 and 16.9 mg/day). Discussion. Measurement of the excretion of THp and alpha - 1 and bet a - 2 MG is a useful addition to present clinical standards for recogn ising early changes in renal function. The increases in the postoperat ive period after cardiac surgery showed tubular damage even in patient s without predictive risk factors or clinical signs. In patients with renal dysfunction open heart surgery and extracorporeal circulation le d to significant tubular damage.