Age-related pathways contributing to altered renal outcomes in the elderly. Multiple pathways interact to produce the changes of renal aging and ↓GFR. Black text indicates implicated upstream effectors of aging, whereas red text reports the functional and histologic changes found in the aged kidney. NO/AA/ANP, nitric oxide/amino acids/atrial natriuretic peptide; SA, senescence associated; TIMP, tissue inhibitors of metalloproteinases; TTKG, trans-tubular potassium gradient.