Effects of lithium on bone resorption in cultured foetal rat long-bones

Increased serum calcium has been observed in manic depressive patients treated with lithium (Li), and one of the mechanisms increasing serum calcium could be a sensitizing effect of Li on bone resorption. In a previous study, however, Li has been found slightly to inhibit PTH-stimulated resorption in cultured foetal rat long-bones. In this work, we extended the study of the effects of Li on bone resorption in culture when resorption of foetal rat long-bones was stimulated by factors other than PTH. Li 3 mM had no effect on basal resorption, a slight and inconsistent inhibitory effect on PTH stimulated bone resorption, a moderate and inconstant inhibitory effect on prostaglandin E2 (PGE2) stimulated resorption, and did not significantly affect the enhancement of resorption by interleukin 1 (IL1). The more constant effect of Li was a nearly complete inhibition of the resorption response to 1,25-dihydroxycholecalciferol (1,25(OH)2D3). This study confirms that Li has no stimulatory effect on bone resorption by itself, nor a sensitizing action on the stimulation of resorption by several activators. Conversely, Li has a striking inhibitory effect on bone resorption stimulated by 1,25(OH)2D3.