DAILY VARIATION IN INFLUENCE OF LITHIUM ON SERUM-CALCIUM CONCENTRATION - A PRELIMINARY-REPORT

1. One millilitre of 5% glucose (vehicle, n= 10) or 1 mL solution of lithium chloride (LiCl) (0.5 or 2.0 mmol/kg per day, n= 10 for each) was injected intraperitoneally in Wistar rats at 10:00 or 22:00 h for 6 days. Blood samples for ionized and total calcium were taken on day 7. 2. Mild elevations in ionized, but not non‐ionized (total‐ionized) calcium were observed following LiCl treatment in both administration times. 3. The increment in ionized calcium was greater when LiCl was injected at 22:00 h than when it was given at 10:00 h. 4. These data indicate that: (1) the influence of lithium on calcium metabolism varies with its administration time; and (2) mild hypercalcaemia induced by the agent mainly depends on the elevation in the ionized fraction of calcium. Copyright © 1990, Wiley Blackwell. All rights reserved