Control of potassium excretion: a Paleolithic perspective.
OBJECTIVE
Regulation of potassium (K) excretion was examined in an experimental setting that reflects the dietary conditions for humans in Paleolithic times (high, episodic intake of K with organic anions; low intake of NaCl), because this is when major control mechanisms were likely to have developed.


RESULTS
The major control of K secretion in this setting is to regulate the number of luminal K channels in the cortical collecting duct. Following a KCl load, the K concentration in the medullary interstitial compartment rose; the likely source of this medullary K was its absorption by the H/K-ATPase in the inner medullary collecting duct. As a result of the higher medullary K concentration, the absorption of Na and Cl was inhibited in the loop of Henle, and this led to an increased distal delivery of a sufficient quantity of Na to raise K excretion markedly, while avoiding a large natriuresis. In addition, because K in the diet was accompanied by 'future' bicarbonate, a role for bicarbonate in the control of K secretion via 'selecting' whether aldosterone would be a NaCl-conserving or a kaliuretic hormone is discussed.


CONCLUSIONS
This way of examining the control of K excretion provides new insights into clinical disorders with an abnormal plasma K concentration secondary to altered K excretion, and also into the pathophysiology of calcium-containing kidney stones.
Halperin
Mitchell L
ML
Renal Division, St. Michael's Hospital, University of Toronto, Toronto, Ontario, Canada. mitchell.halperin@utoronto.ca
Cheema-Dhadli
Surinder
S
Lin
Shih-Hua
SH
Kamel
Kamel S
KS
D000818:Animals; D006801:Humans; D007669:Kidney Calculi / Q000097:blood / Q000201:enzymology* / Q000652:urine; D007685:Kidney Tubules, Collecting / Q000201:enzymology* / Q000473:pathology; D008138:Loop of Henle / Q000201:enzymology* / Q000473:pathology; D009318:Natriuresis; D011188:Potassium / Q000097:blood* / Q000652:urine; D051381:Rats; D012965:Sodium Chloride / Q000097:blood / Q000652:urine; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014882:Water-Electrolyte Balance
D012965:Sodium Chloride; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium