Hypersecretion of submandibular saliva in male mice: trophic response in small intestine

The submandibular salivary gland of the male mouse and its secretions contain growth-promoting factors that accelerate cell proliferation in vitro and also have effects on the gastrointestinal tract in vivo. We therefore stimulated salivary secretion with isoproterenol for studies of the effects of submandibular saliva on intestinal cell proliferation; only submandibular glands respond to isoproterenol by releasing epidermal growth factors and other growth factors into the saliva. Submandibular sialadenectomized and sham sialadenectomized male mice on pair-feeding schedules were given isoproterenol intraperitoneally for 1 wk. A 44% increase in ribonucleic acid and a 13% increase in deoxyribonucleic acid were observed in the jejunum of animals with intact submandibular glands (p less than 0.001). In the ileum, there was a 26% increase in ribonucleic acid, a 47% increase in deoxyribonucleic acid, and a 28% increase in deoxyribonucleic acid specific activity (p less than 0.001). Morphometric measurements showed a 28% increase in villous height (p less than 0.001). No differences were found in colonic mucosa. Submandibular saliva increases the nucleic-acid content of mucosal cells and the villous height in the small intestine of male mice, presumably in part because of the growth factors it contains; a systemic metabolic change could also be present.