On the influence of extracellular fluid volume expansion and of uremia on bicarbonate reabsorption in man

Abstract

A B S T R A C T The patterns of bicarbonate reabsorption during increasing plasma concentrations were studied in subjects with a range of glomerular filtration rates (GFR) from 170 to 2 ml/min. In a group of five subjects with GFR values above 30 ml/min, paired bicarbonate titration studies were performed first under conditions which minimized extracellular fluid (ECF)

Effects of extracellular fluid volume and plasma bicarbonate concentration on proximal acidification in the rat.

“…Bicarbonate Ringer's expansion predictably decreased hematocrit and plasma protein concentration (Table II). When tubules were perfused with 24 mM bicarbonate 5 In the calculation of a driving force for bicarbonate diffusion, PD was not included. Using a similar perfusate, Fromter et al (16) have measured a transepithelial PD of +1.4 mV.…”

“…Clearance studies in dogs, rats, and man have all demonstrated that ECF volume expansion inhibits fractional bicarbonate reabsorption (3)(4)(5)(6)8). A prevalent view has been that this inhibition occurs in the proximal tubule and is related to increased bicarbonate back leak (20).…”

“…Numerous clearance and micropuncture studies have attempted to examine the effects of systemic bicarbonate concentration and ECF' volume status on acidification (1)(2)(3)(4)(5)(6)(7)(8). In these studies, however, as plasma bicarbonate concentration or ECF volume were altered, there were simultaneous changes in luminal bicarbonate concentration and/or flow rate.…”

High sodium chloride intake exacerbates immobilization-induced bone resorption and protein losses

“…But still other possible mechanisms may be involved, as previously mentioned (25). Enforced activity of cellular Na ϩ /H ϩ exchangers (18,36) as well as Na ϩ /H ϩ ion exchanges on the extracellular glycosaminoglycans (19) and/or a Na-induced expansion of extracellular volume, resulting in a decrease in HCO 3 Ϫ reabsorption (3,38,52,58), can contribute to mediation of the effect of NaCl on acid-base balance. Summarizing, with high NaCl intake, renal loss of bicarbonate but also excess acid production could be reasonably expected to affect acid-base status.…”

A Case of Anorexia Nervosa with Acute Renal Failure Induced by Rhabdomyolysis; Possible Involvement of Hypophosphatemia or Phosphate Depletion.

“…The former would be due to hypoventilation, often seen in patients with hypophosphatemia (ll, 12); and the latter due to dehydration-induced secondary aldosteronism. The high urine pH may be explained by the overflow of HCO3~ which was exaggerated by the rehydration (13). Although elevated GOT, GPT, LDH, ALP, and BUN in the serum were corrected successfully by intravenous nutrition (400-800kcal/day) and fluid (1,600-2,500 ml/day) administration, serum phosphate concentration decreased drastically, and acute renal failure followed (Fig.…”