Control of excretion of potassium: lessons from studies during prolonged total fasting in human subjects.
A deficit of K+ of close to 300 mmol develops in the first 2 wk of fasting, but little further excretion of K+ occurs, despite high levels of aldosterone and the delivery of ketoacid anions that are not reabsorbed in the distal nephron. Our purpose was to evaluate how aldosterone could have primarily NaCl-retaining, rather than kaliuretic, properties in this setting. To evaluate the role of distal delivery of Na+, four fasted subjects received an acute infusion of NaCl to induce a natriuresis. To assess the role of distal delivery of HCO3-, five fasted subjects were given an infusion containing NaHCO3. The natriuresis induced by an infusion of NaCl caused only a small rise in the rate of excretion of K+ (0.8 +/- 0.1 to 1.9 +/- 0.3 mmol/h); in contrast, when HCO3- replaced Cl- in the infusate, K+ excretion rose to 8.3 +/- 2.2 mmol/h, despite little excretion of HCO3- (urine, pH 5.8) and similar rates of excretion of Na+. The transtubular K+ concentration gradient was 19 +/- 3 with HCO3- and 6 +/- 2 with NaCl. We conclude that the infusion of NaHCO3 led to an increase in K+ excretion, likely reflecting an increased rate of distal K+ secretion. With a low distal delivery of HCO3-, aldosterone acts as a NaCl-retaining, rather than a kaliuretic, hormone.
Lin
S H
SH
Renal Division, National Defense Medical Center, Taipei, Taiwan, Republic of China.
Cheema-Dhadli
S
S
Gowrishankar
M
M
Marliss
E B
EB
Kamel
K S
KS
Halperin
M L
ML
D000328:Adult; D000450:Aldosterone / Q000502:physiology; D004231:Diuresis; D004573:Electrolytes / Q000097:blood / Q000652:urine; D005215:Fasting / Q000652:urine*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007262:Infusions, Intravenous; D007668:Kidney / Q000502:physiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009318:Natriuresis; D009765:Obesity / Q000178:diet therapy; D011188:Potassium / Q000652:urine*; D011189:Potassium Chloride / Q000627:therapeutic use; D012965:Sodium Chloride / Q000008:administration & dosage / Q000494:pharmacology; D013997:Time Factors
D004573:Electrolytes; D012965:Sodium Chloride; D000450:Aldosterone; D011189:Potassium Chloride; D011188:Potassium