Effects of storage conditions on results for quantitative and qualitative evaluation of proteins in canine urine.

OBJECTIVE To investigate effects of storage conditions on the canine urine protein-to-creatinine ratio (UPC) and on SDS-agarose gel electrophoresis (AGE) of urinary proteins. SAMPLE Urine specimens from 20 proteinuric (UPC > 0.5) and 20 nonproteinuric (UPC ≤ 0.2) dogs. PROCEDURES UPC and SDS-AGE were performed on urine specimens stored at room temperature (20°C) and 4°C for up to 5 days and at -20° and -80°C for up to 360 days; some specimens were subjected to 3 freeze-thaw cycles. Results were compared with those obtained for fresh urine specimens. RESULTS UPC was not affected by storage at room temperature or by freezing. A decrease in UPC was observed for specimens from nonproteinuric dogs after 5 days at 4°C (10%) and from both groups after 90 days at -20° and -80°C (≤ 20% and ≤ 15%, respectively). The SDS-AGE profiles revealed no visual changes regardless of duration of storage for specimens stored at room temperature, 4°C, and -80°C, except for 1 profile after 360 days at -80°C. Repeated freeze-thaw cycles did not affect SDS-AGE profiles. Appearance or strengthening of high-molecular-weight bands that could alter interpretation was evident in SDS-AGE profiles after storage at -20°C for ≥ 15 days (31/40 dogs). CONCLUSIONS AND CLINICAL RELEVANCE Storage of urine at -20° or -80°C for up to 1 year influenced the UPC without affecting clinical interpretation. Storage of urine specimens at -20°C impaired visual analysis of SDS-AGE. When SDS-AGE cannot be performed on fresh or recently refrigerated urine specimens, storage at -80°C is recommended.

Characterization of Proteinuria in Dogue de Bordeaux Dogs, a Breed Predisposed to a Familial Glomerulonephropathy: A Retrospective Study.

Dogue de Bordeaux dog has been reported to be predisposed to a familial glomerulonephropathy that displays some morphological modifications reported in focal and segmental glomerulosclerosis. Prevalence of quantitatively abnormal renal proteinuria was recently reported to be 33% in this breed. The nature of the proteinuria was assessed by sodium dodecyl sulfate-agarose gel electrophoresis and determinations of urinary markers (urinary retinol-binding protein, urinary N-acetyl-ß-glucosaminidase, urinary albumin and urinary immunoglobulin G) on stored specimens. Diagnostic performances of sodium dodecyl sulfate-agarose gel electrophoresis to identify dogs with elevated urinary biomarkers were assessed. Samples from 102 adult Dogue de Bordeaux dogs (47 non-proteinuric [urine protein-to-creatinine ratio ≤ 0.2], 20 borderline-proteinuric [0.2< urine protein-to-creatinine ratio ≤ 0.5] and 35 proteinuric dogs [urine protein-to-creatinine ratio >0.5]) were used, of which 2 were suffering from familial glomerulonephropathy. The electrophoretic protein patterns, for all but one proteinuric dog, were indicative of a glomerular origin and, in all dogs, the urinary albumin concentration related to creatinine concentration and the urinary immunoglobulin G concentration related to creatinine concentration were above the upper limit of the reference interval established for the breed. Sensitivity and specificity of sodium dodecyl sulfate-agarose gel electrophoresis identifying dogs with elevated urinary albumin concentration were 94% and 92%, respectively, while diagnostic performance of sodium dodecyl sulfate-agarose gel electrophoresis in detecting dogs with elevated urinary immunoglobulin G concentration yielded sensitivity and specificity of 90% and 74%, respectively. These results suggest that all proteinuric and some borderline-proteinuric Dogue de Bordeaux dogs likely have underlying glomerular lesions and that sodium dodecyl sulfate-agarose gel electrophoresis and urinary markers might be useful to screen dogs with borderline-proteinuria. Additional investigations are warranted to assess if these findings are related to the familial glomerulonephropathy.