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Urinary protein > Background Section

Normally the glomerular filtration permeability barrier, which is composed of podocyte, glomerular basement membrane and endothelial cells, prevents serum protein from leaking into urine. Albuminuira usually reflects injury of glomerular permeability barrier.

Albuminuria can be measured in mice by both albumin:creatinine ratios (ACR) determined on spot urine obtained on a single urine collection of 10µl, or total daily albumin excretion obtained on a 24 hour urine collection from mice individually housed in metabolism cages. Notably the amino acid sequence of albumin is highly heterogeneous between species with only ~70% homology between human and rat. For this reason species-specific ELISA kits must be used. Albumin will be measured using a mouse specific ELISA kit (Albuwell M kit EXOCELL, Inc). A significant correlation between ACR and 24h albumin excretion has been documented by our group (4), so initial screening will be performed using the ACR determination. Using this kit our studies demonstrated that ACR values of >100µg alb/mg Creatinine are indicative of abnormal glomerular albumin sieving in diabetic C57BL6 mice. This is also true for most, but not all, other diabetic strains. For instance control KK mice (non STZ treated) exhibit a profound albuminuria. Increased albumin excretion can be confirmed (if desired) on the 24 hour urine collection. Details of this protocol are included on the protocol page for this segment.

For detection of albumin/creatinine ratio (ACR; expressed as µg/mg), a 20-µl to 200-µl volume of spot urine is collected from each mouse. Urinary albumin is detected using Albuwell M kit, and urinary creatinine is measured using the Creatinine Companion murine ELISA kit (Exocell, Philadelphia, PA). For determination of 24-h urinary albumin excretion rate, urine is collected in metabolic cages, and 24 h urinary excretion levels in urine, expressed as µg/24 h, also are assayed with Albuwell M assay kit.

Publications for Urinary protein (1)

Qi Z, Fujita H, Jin J, Davis LS, Wang Y, Fogo AB, Breyer MD. Characterization of susceptibility of inbred mouse strains to diabetic nephropathy. Diabetes (2005) 54:2628-37
View abstract View in PubMed

Differential susceptibility to diabetic nephropathy has been observed in humans, but it has not been well defined in inbred strains of mice. The present studies characterized the severity of diabetic nephropathy in six inbred mouse strains including C57BL/6J, DBA/2J, FVB/NJ, MRL/MpJ, A/J, and KK/HlJ mice. Diabetes mellitus was induced using low-dose streptozotocin injection. Progression of renal injury was evaluated by serial measurements of urinary albumin excretion, glomerular filtration rate (GFR), and terminal assessment of renal morphology over 25 weeks. Despite comparable levels of hyperglycemia, urinary albumin excretion and renal histopathological changes were dramatically different among strains. DBA/2J and KK/HlJ mice developed significantly more albuminuria than C57BL/6J, MRL/MpJ, and A/J mice. Severe glomerular mesangial expansion, nodular glomerulosclerosis, and arteriolar hyalinosis were observed in diabetic DBA/2J and KK/HlJ mice. Glomerular hyperfiltration was observed in all diabetic strains studied except A/J. The significant decline in GFR was not evident over the 25-week period of study, but diabetic DBA/2J mice exhibited a tendency for GFR to decline. Taken together, these results indicate that differential susceptibility to diabetic nephropathy exists in inbred mice. DBA/2J and KK/HlJ mice are more prone to diabetic nephropathy, whereas the most widely used C57BL/6J mice are relatively resistant to development of diabetic nephropathy.

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Last updated on 2013-11-06 Moderated by Jimmy Hao