The influence of body posture on lithium clearance

A L Kamper, S Strandgaard, N H Holstein-Rathlou, O Munck, P P Leyssac

13 Citationer (Scopus)

Abstract

To establish appropriate standard circumstances for lithium clearance measurements, a study was undertaken in 12 healthy volunteers. In each subject, the glomerular filtration rate (GFR), as estimated by [51Cr]EDTA plasma clearance, and the renal clearances of lithium, sodium and potassium were measured four times at 1-week intervals: two in the supine and one in the sitting position, and one when the subject was walking around. Glomerular filtration rate was not influenced by posture changes. On the contrary, lithium clearance, which in the supine position was 30 +/- 9 ml/min (1 SD), tended to fall in the sitting position, and fell significantly to 26 +/- 5 ml/min (p less than 0.025) in walking subjects. Absolute proximal tubular reabsorption rate of fluid correspondingly rose from 83 +/- 16 to 92 +/- 15 ml/min (p less than 0.005) and sodium clearance fell from 1.52 +/- 0.81 to 1.00 +/- 0.52 ml/min (p less than 0.05) in walking subjects. Absolute distal reabsorption of sodium decreased during walking from 4052 +/- 1219 to 3449 +/- 658 mumol/min (p less than 0.025), while fractional distal reabsorption of sodium was unchanged. Our results show a rise in proximal tubular reabsorption during moderate physical activity. Hence, when renal tubular function is studied with the lithium clearance method, standardization of posture and physical activity is important. In such studies physical activity such as walking should particularly be avoided.

OriginalsprogEngelsk
TidsskriftScandinavian Journal of Clinical & Laboratory Investigation
Vol/bind48
Udgave nummer6
Sider (fra-til)509-12
Antal sider4
ISSN0036-5513
StatusUdgivet - okt. 1988
Udgivet eksterntJa

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