| Factor | Proposed Mechanism |
|---|---|
| Decreased GFR | Increases fractional bicarbonate reabsorption and prevents elevated plasma bicarbonate concentrations from exceeding Tm |
| Volume contraction | Stimulates proximal tubular bicarbonate reabsorption |
| Hypokalemia | Decreases GFR and increases proximal tubular bicarbonate reabsorption Stimulates sodium-independent, potassium-dependent (low) secretion in cortical collecting tubules |
| Hypochloremia* | Increases renin |
| Decreases distal chloride delivery | |
| Passive backflux of bicarbonate | Creates a favorable concentration gradient for passive bicarbonate movement from proximal tubular lumen to blood |
| Aldosterone | Increases sodium-dependent proton secretion in cortical collecting tubules and sodium-independent proton secretion in cortical collecting tubules and medullary collecting tubules |
GFR = glomerular filtrate rate; Tm.