Early and late adjustment to potassium loading in humans.
We studied the adaptation to early (72 hr) and late (20 days) K loading (400 mmol/day, 4 equal meals every 6 hour) in six healthy humans. Throughout the study, each single K meal was followed by an acute transient rise in plasma K, aldosterone and kaliuresis. "K balance" (urinary K excretion approximately 80% of intake) was achieved in the second 24 hour period of K loading. This was associated with elevated plasma K and aldosterone, slightly negative sodium (Na) balance and stimulated plasma renin activity. At 20 days of K loading Na loss had been compensated. Plasma renin activity and aldosterone had returned to baseline, although the latter kept increasing after each single K meal. Compared to the first K meal, the K meals at 72 hours and 20 days of K loading were followed by more kaliuresis, while the natriuretic effect had disappeared. Abrupt discontinuation of K loading was followed by negative K balance, lasting only 24 hour, and by Na retention, lasting 72 hours. In conclusion, switching to a high K diet in humans is immediately followed by increased renal K excretion, and by Na loss. K excretion increases over a few days, while Na loss is halted. This can be explained by the rise in plasma aldosterone, secondary to elevated plasma K and renin activity. After weeks, renal adaptation forms an additional factor promoting K excretion and preventing natriuresis. The latter appears specifically from the Na retention which occurs after discontinuation of K loading in the absence of persistent aldosterone stimulation.
Rabelink
T J
TJ
Department of Nephrology and Hypertension, University Hospital Utrecht, The Netherlands.
Koomans
H A
HA
Hené
R J
RJ
Dorhout Mees
E J
EJ
D000222:Adaptation, Physiological / Q000502:physiology; D000328:Adult; D000450:Aldosterone / Q000097:blood; D004032:Diet; D005260:Female; D006801:Humans; D007668:Kidney / Q000502:physiology*; D008297:Male; D009318:Natriuresis / Q000502:physiology; D011188:Potassium / Q000008:administration & dosage* / Q000378:metabolism; D012083:Renin / Q000097:blood; D013997:Time Factors; D014882:Water-Electrolyte Balance / Q000502:physiology
D000450:Aldosterone; D012083:Renin; D011188:Potassium