While the clinical relevance of proteinuria, and especially albuminuria, has been well documented the quantitative mechanistic contribution or role of different barrier components to albuminuria remains an area of considerable excitement and debate. Recent data from several laboratories utilizing different scientific approaches have delineated a potential role of proximal tubules in albumin reabsorption and reclamation as another important determinant of the urinary barrier to albuminuria. Therefore, the present application proposes to dissect apart and quantify glomerular and proximal tubule contributions to albuminuria under physiologic and disease conditions in a longitudinal fashion in the same rats. Structural, functional and mechanistic observations will be interrelated to advance our present understanding of this clinically important phenomenon. Our Overall Hypothesis is that both glomerular permeability and proximal tubule cells play fundamental, physiologic, synergistic, interactive and inducible roles to try and maintain the physiological state and minimize albuminuria. We further hypothesize that acute or chronic alterations in glomerular albumin permeability or in proximal tubule albumin reclamation can directly affect albuminuria. To directly evaluate this hypothesis we have developed the necessary techniques, approaches and animal models to dissect, quantify, understand and interrelate the role of acute and chronic changes in glomerular permeability and proximal tubular cell reabsorption and transcytosis of filtered albumin.

Public Health Relevance

While the importance of protein (albumin) in the urine in disease progression is known, the key mechanism(s) mediating the presence of and toxic effects of albumin still remain to be determined. The proposed studies will lead to an enhanced mechanistic understanding of the cellular processes involved in albuminuria, their role in disease processes resulting in proteinuria thereby leading the way toward development of possible novel therapeutic approaches.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Pathobiology of Kidney Disease Study Section (PBKD)
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Rys-Sikora, Krystyna E
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Indiana University-Purdue University at Indianapolis
Internal Medicine/Medicine
Schools of Medicine
United States
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Molitoris, Bruce A; Reilly, Erinn S (2016) Quantifying Glomerular Filtration Rates in Acute Kidney Injury: A Requirement for Translational Success. Semin Nephrol 36:31-41
Wagner, Mark C; Campos-Bilderback, Silvia B; Chowdhury, Mahboob et al. (2016) Proximal Tubules Have the Capacity to Regulate Uptake of Albumin. J Am Soc Nephrol 27:482-94
Molitoris, Bruce A (2014) Using 2-photon microscopy to understand albuminuria. Trans Am Clin Climatol Assoc 125:343-56; discussion 356-7
Sandoval, Ruben M; Wang, Exing; Molitoris, Bruce A (2014) Finding the bottom and using it: Offsets and sensitivity in the detection of low intensity values in vivo with 2-photon microscopy. Intravital 2:
Hall, Andrew M; Molitoris, Bruce A (2014) Dynamic multiphoton microscopy: focusing light on acute kidney injury. Physiology (Bethesda) 29:334-42
Dickson, Landon E; Wagner, Mark C; Sandoval, Ruben M et al. (2014) The proximal tubule and albuminuria: really! J Am Soc Nephrol 25:443-53
Sandoval, Ruben M; Molitoris, Bruce A (2013) Quantifying glomerular permeability of fluorescent macromolecules using 2-photon microscopy in Munich Wistar rats. J Vis Exp :
Saleh, Mohamed A; Sandoval, Ruben M; Rhodes, George J et al. (2012) Chronic endothelin-1 infusion elevates glomerular sieving coefficient and proximal tubular albumin reuptake in the rat. Life Sci 91:634-7