GLOMERULAR METALLOPROTEASE ACTIVITY IN THE AGING RAT-KIDNEY - INVERSECORRELATION WITH INJURY

Glomerular metalloprotease activity (phenanthroline inhibitable) was m easured in cortical homogenates from rat kidneys by use of the rate of degradation of H-3-denatured type I collagen (gelatin). Glomerular me talloprotease activity was similar in male and female kidneys from kid neys from young (4 months) rats (27 +/- 7 and 34 +/- 6 mug of (H-3)-ge latin degraded/h per milligram of glomerular protein, respectively). G lomerular metalloprotease activity was unaltered by age (18 to 20 mont hs) in intact males but increased two times in old intact females, cas trated males, and ovariectomized females. These aging changes correlat ed inversely with the level of age-dependent glomerular injury, i.e., old intact males had substantially greater glomerular damage than all other old groups. These observations suggest (1) that the androgens ar e a risk factor for the development of age-dependent glomerular damage : and (2) that an age-dependent increase in glomerular metalloprotease activity may protect against damage by limiting the build-up of glome rular extracellular matrix.