[Effect of lithium hydroxybutyrate on the circadian dynamics of the urinary excretion of Li(+), Na(+), K(+), and Ca(2+) in rats depending on the circadian phase of the drug administration].

In winter solstice, the urinary excretion of Li+ and Na+ in intact rats has a uniform circadian profile, while K+ and Ca2+ exhibit a 23-h and 24-h rhythm, respectively. The administration of lithium hydroxybutyrate (10 mg/kg, 6 days) at 8 a.m. forms the 24-h Li+ and Na+ excretion rhythm, while not significantly affecting the circadian profiles of K+ and Ca2+. The lithium loading at 8 p.m. made the circadian urinary excretion profiles of Ca2+ and Na+ uniform, while the excretion of Li+ and K+ acquired a 24-h rhythm. Irrespective of the circadian phase, the administration of lithium hydroxybutyrate decreased the average daily concentration of Na+ in the urine, while the average concentration of Ca2+ remains unchanged; the concentration of K+ decreases after lithium hydroxybutyrate injections in the morning. Upon the morning treatment, lithium cations are excreted faster than after the evening injections.