Date of Award

3-28-2007

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

First Advisor

Edward C. Carlson

Abstract

Experimental evidence suggests that disease- and age-related thickening of glomerular (GBM) and tubular (TBM) basement membranes may be related to increases in reactive oxygen species (ROS). Studies also suggest that antioxidants may function as renoprotectants against such ROS-induced damage. The current study focuses on metallothionein-I/II (MT-I/II) and glutathione (GSH), both of which exhibit potent antioxidant functions. Ames dwarf mice, which exhibit elevated tissue antioxidant levels (catalase, Cu/Zn superoxide dismutase, GSH) and an average life span significantly greater (50-65%) than wild type controls, were used to test our hypothesis that increased levels of renal MT-I/II and GSH are concomitant with decreased measurements of renal basement membrane thickening. Interestingly, TEM morphometry data demonstrated that with increasing age, both the GBMs and TBMs of dwarf animals were thinner (3.123.6% and 21.8-39.1%, respectively) than those of age-matched controls. These data were consistent with our hypothesis and immunohistochemical results that showed increased MT-I/II staining in dwarf kidneys relative to age-matched controls at all ages. In dwarfs, MT-I/II was localized to renal tubules in young mice, but also appeared in glomeruli with increasing age. A competitive ELISA assay was developed to quantitate both endogenously polymerized and "total" (glutaraldehyde-polymerized) renal MT-I/II while renal GSH levels were determined by fluorimetry. At 90, 300, 600, and 720 days, dwarf renal MT-I/II and GSH levels were significantly higher than controls. Since MT-I/II and GSH are well-documented ROS scavengers, it seems possible that in the long lived Ames dwarf model of delayed aging, increased endogenous antioxidant levels provide renoprotection from oxidative damage and lead to reduced quantities of age-related GBM and TBM thickening.

Download

Share

COinS