Rat RPA-1

Renal Papillary Antigen 1 and Renal Injury

Renal Papillary Antigen 1 (RPA-1) is found exclusively in the collecting duct epithelial cells of rats. RPA-1 was developed using Argutus' patented biomarker discovery technology, Histomics^®. RPA-1 is released into the urine of rats that are experiencing collecting duct or papillary injury. RPA-1 has proven to be the optimal biomarker for experimental renal papillary necrosis (RPN) and collecting duct injury, serious conditions for which biomarkers are currently lacking.

The image on the right shows the specific IHC staining using anti rat RPA-1 antibody (in orange). This is an entire healthy rat kidney cross-section demonstrating the presence of RPA-1 in collecting duct cells. Upon injury to these epithelial cells the RPA-1 antigens are released into urine and can be subsequently analysed using the Argutus Medical Rat RPA-1 EIA assay.

Renal Papillary Antigen 1 EIA

The RPA-1 ELISA is a simple microassay based EIA to measure renal papillary antigen 1 in rat urine. Together with rat alpha GST and GST Yb1 it provides a broad picture of nephron status from a single urine sample.

The test procedure is based on the sequential addition of sample, anti rat RPA-1 - enzyme conjugate, and substrate to microassay wells coated with anti rat RPA1. The resultant color intensity is proportional to the amount of alpha GST present in the sample. The assay range is 3.12-100 RPA-1 units/L.

Recent News on RPA-1

Rat RPA-1 was included in the ILSI HESI Nephrotoxicity Working Group project and its performance assessed compared to the traditional markers used in toxicity / safety testing. The results of this study have been presented at many conferences, most notably the Society of Toxicology meetings in 2007 and 2008. In May 2008 the rat RPA-1 data was submitted to the FDA / EMEA along with another 2 biomarkers (alpha GST and Clusterin) under the VxDs qualification scheme. It is expected to be fully qualified early in 2009.

The RPA-1 ELISA proved valuable in being the only biomarker specific for collecting duct injury and as such the only marker capable of conclusively identifying renal papillary necrosis (RPN). The IHC specificity has been demonstrated in a number of studies and was recently used as the front cover image in the 36^th volume of Toxicological Pathology 2008.