Lethal factor in the male mouse submandibular gland.

The presence of a toxic component (lethal factor) has been reported in the male mouse submandibular gland (SMG). This study was designed to clarify whether the toxic component was secreted into saliva or not and to investigate some characteristics of the component. Not only SMG extract but also phenylephrine-induced saliva from male mice was highly toxic to guinea pigs, rats, hamsters, and mice. The toxic activity of the saliva was found in all strains of male mice examined. In female mice, the toxic activity was extremely low. One of the toxic components in the saliva was purified by isoelectric focusing and DEAE Sephadex A-50 chromatography and identified with a kallikrein-like enzyme. The activity of the enzyme markedly increased in saliva secreted to alpha-adrenergic agents but not to beta-adrenergic or cholinergic agents. These results indicate that the lethal factor in the male mouse SMG is an exocrine protein with Kallikrein activity and its secretion into saliva is controlled through alpha-adrenergic receptors.