Further studies of the neutralization of silica toxicity in vitro.

A previous paper (Marks, 1957) describes work done on a number of substances to ascertain their protective effect on phagocytic cells in tissue culture against injury by silica dust. The most potent of those investigated was 48-80, a drug used in experimental pharmacology to release histamine from mast cells. In the present paper, several drugs related to compound 48-80 have been examined for their capacity to protect phagocytic cells against the toxic effect of silica dust in vitro. It is shown that protection can be dissociated from histamine-releasing activity in these compounds. Other substances found to neutralize the toxicity of silica dust were certain phenazines, complexes of aluminium with chelating agents, and the histamine-releasing agent L 1935.