Diurnal Variations in Serum Lithium and Renal Lithium Clearance in Rats given Lithium as a Single Small Dose or as Multiple High Doses

Abstract

Clearance determinations were carried out in three groups of rats: A high lithium group given food to which 70 mmol/kg of lithium were added for 4-6 weeks leading to a mean serum lithium concentration of 0.85 mmol/l, a low lithium group given food to which 15 mmol/kg of lithium were added for two days before the clearance period leading to a mean serum lithium concentration of 0.22 mmol/l, and a group given the same food without lithium. The sodium and potassium contents of the food were kept high in order to avoid lithium-induced development of negative sodium balance and excessive polyuria. The rats were housed in four rooms with 6-hour displaced 24-hour light-dark cycles. The results showed that high doses of lithium led to a significant increase of the lithium clearance and the urine flow. Small amounts of lithium influenced neither the clearance values nor the urine flow. All renal variables were increased by about 50-100% during the dark period. The serum lithium concentration was least influenced by the diurnal rhythm. It is concluded that serum lithium concentrations measured at any time of the day are fairly representative of the 24 hours. A lithium clearance measured during daytime is valid for this period only. Long-term lithium treatment leads to an increase of the renal lithium clearance but does not diminish the normal diurnal rhythm of the kidney function.

Proximal tubular function in adult rats treated neonatally with enalapril

“…Prior to clearance experiments rats had free access to normal, pelleted rat chow (Na + ; 120 mmol kg −1 , K + ; 153 mmol kg −1 ). Two days before experimentation the food was switched to a powdered rat chow with a similar sodium and potassium content, supplemented with LiCl (10 mmol kg −1 ), in order to produce a plasma Li concentration ( P Li ) of ≈0.2 mmol L −1 , which is below the level at which Li, per se , interferes with renal function ( Olesen & Thomsen 1985). Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured by the urinary clearances of 51 Cr‐ethylenediaminetetraacetic acid (EDTA; Amersham Laboratories; Buckinghamshire, UK) and 125 I‐hippuran (Institutt før Energiteknikk, Kjeller, Norway), respectively.…”

The Natriuretic Effect of an Acute Peroral Load of Potassium Chloride after Inhibition of Potassium Secretion with Amiloride or Lithium

“…Two days before the clearance study 15 mmol of LiCl were added to the food of control rats and rats given amiloride. This amount of lithium leads to serum lithium concentrations of about 0.2 mmol/l, concentrations which are too low to influence the kidney function but sufficiently high to be measured accurately (Olesen & Thomsen 1985).…”

“…CL, was used as a measure of Vpror Shirley et al 1983;Thomsen 1984). The sodium excretion expressed as a fraction of the amount delivered to the distal nephron was calculated as CNJCL,.…”

Effects of Recovery from Anesthesia and Surgery on Renal Sodium Handling in Conscious Rats

“…This dose o f lithium led to serum lithium concentra tions within the range o f 0.15-0.25 mmol/1. which are too low to affect kidney function but sufficiently high to permit an accurate determination o f Cu [8].…”