Immunological detection of glutamyl aminopeptidase in urine samples from cisplatin-treated rats

Purpose: The aim of this work is to demonstrate if urinary excretion of glutamyl aminopeptidase (GluAp) can be quantified by immunological methods. Experimental design: Urine samples from control and cisplatin-treated rats (n = 10 each group) were obtained at 1, 8, and 15 days after cisplatin injection. GluAp was analyzed by kinetic fluorimetry, ELISA, and immunoblotting. Sensitivity and specificity was studied for fluorimetric activity and ELISA 24 h after cisplatin injection. We also analyzed the predictive value over renal dysfunction at the end of the experiment. Results: GluAp was easily detected by immunoblotting and ELISA, and its urinary excretion was increased in cisplatin-treated rats (p < 0.01). Results obtained with ELISA were strongly correlated (r=0.8186; p<0.0001) with fluorimetric activity. Kinetic fluorimetry was the method with the highest AUC (AUC = 1) and the highest predictive value over serum creatinine (r = 0.7630; p = 0.0001) and body weight increase (r = -0.8721; p < 0.0001). Conclusions and clinical relevance: GluAp can be detected in urine samples with immunological methods, making possible the development of an antibody-based kit for its determination. Its excretion correlates with the extent of renal dysfunction in cisplatin-treated rats, confirming its value as an early marker of renal damage that can be a diagnostic aid in renal diseases.