Table 2.

Kidney functional changes with aging and declining GFR.

Impairment in vasodilation response in renal hemodynamics
• Greater sensitivity to vasoconstrictor stimuli (angiotensin, norepinephrine and endothelin). • Reduced vasodilatory response (acetylcholine, dopamine and nitric oxide).
Decreased capacity to concentrate and dilute urine • Urinary concentration Reduced capacity to conserve water and solutes under water deprivation. • Urinary dilution Decreased diluting capacity after fluid overload, possibly due to a defect to generate free water.
Impaired renal regulation of sodium/potassium balance • Sodium Lower capacity to reduce sodium excretion under sodium restriction. Lower capacity to excrete sodium under sodium load, leading to sodium retention and fluid volume expansion. • Potassium Lower capacity to decrease potassium excretion under high potassium diet
Acid-base dysregulation • Reduced capacity to buffer metabolic changes • Reduced capacity to excrete the excess H+ load and ammonium
Calcium homeostasis • Impaired vitamin D production in the skin • Impaired production of 1,25-(OH)2D3 • Increased PTH secretion • High FGF23 levels