Inhibition of bone resorption in tissue culture by H1-receptor antagonists

Mouse bone culture studies show that several representative H1-receptor antagonists, promethazine hydrochloride, pyrilamine maleate, tripelennamine hydrochloride, and diphenhydramine hydrochloride, inhibit parathyroid extract-stimulated bone resorption. The H2-receptor antagonists, metiamide and cimetidine, are ineffective. In view of the finding that histamine and histamine agonists did not stimulate bone resorption, it is unlikely that histamine receptors are involved in mediating parathyroid extract-stimulated bone resorption. Because H1-receptor antagonists bind to phospholipids and have been shown to influence membrane structure and function, it is suggested that they inhibit bone resorption by a mechanism that depends on their membrane-stabilizing effect.