Stimulation by in Vivo and in VitroMetabolic Acidosis of Expression of rBSC-1, the Na+-K+(NH4+)-2Cl−Cotransporter of the Rat Medullary Thick Ascending Limb

Acid-Base Status Determines the Renal Expression of Ca2+ and Mg2+ Transport Proteins

“…Acetazolamide treatment was associated with increased urine volume and Na ϩ excretion, which has been shown to result in extracellular volume contraction and enhanced NKCC2 activity (45,46). Furthermore, metabolic acidosis, which developed in acetazolamide-treated wild-type mice, was previously shown to increase NKCC2 mRNA and protein abundance (14,47). Thus, we postulate that these additive stimulatory effects enhance passive Mg 2ϩ reabsorption in TAL.…”

“…Earlier studies, including micropuncture experiments, suggested that systemic acid-base disturbances specifically influence Ca 2ϩ and Mg 2ϩ reabsorption in DCT/CNT (2,10). Hypothetically, regulation of Ca 2ϩ and Mg 2ϩ transport proteins in these nephron segments could be involved in the altered renal divalent excretion secondary to changes in acid-base status, as was shown for other renal transporters and channels (11)(12)(13)(14). We previously demonstrated that tacrolimus (FK506)-induced Ca 2ϩ and Mg 2ϩ wasting as well as thiazide-induced hypomag-nesemia are associated with decreased renal expression of Ca 2ϩ and/or Mg 2ϩ transporters (15,16).…”

Molecular Mechanisms of Acid-Base Sensing by the Kidney

“…50 A similar mechanism involving z-crystallin has been proposed to enhance mRNA and protein expression of the loop-diuretic-sensitive NKCC2 cotransporter in the TAL. [51][52][53] Whether any of the pH sensors described above are involved in these processes is unknown.…”

Molecular Mechanisms of Renal Ammonia Transport

“…Changes in NKCC-2 protein expression are a major component of the increase in MTAL ammonia absorption that occurs with chronic metabolic acidosis (27,53). Increased mRNA expression precedes increased protein expression (53); the elevation in systemic glucocorticoids that occurs with chronic metabolic acidosis may mediate the increases in mRNA and protein expression (54).…”

“…Increased mRNA expression precedes increased protein expression (53); the elevation in systemic glucocorticoids that occurs with chronic metabolic acidosis may mediate the increases in mRNA and protein expression (54). Changes in cell-surface expression of NKCC-2 can regulate NKCC-2 ion transport in response to other stimuli such as cAMP (55); whether this mechanism is important for the regulation of ammonia transport is unknown.…”