β-Adrenergic Stimulation of c- <i>fos</i> Gene Expression in the Mouse Submandibular Gland

Abstract

Isoproterenol (IPR), a beta-adrenergic agonist, induces division of acinar cells in the parotid and submandibular glands of adult rodents and produces hyperplastic and hypertrophic enlargements of these organs. We analyzed the effects of IPR on thymidine incorporation, c-fos mRNA levels, and the immunocytochemical localization of c-fos protein in the submandibular glands of adult and of 5- and 14-day-old mice. In the glands of untreated mice c-fos transcripts were not detectable. In all experimental groups, administration of IPR led to a rapid, transient increase in the c-fos mRNA level. Propranolol blocked the IPR effect, while treatment with IPR and cycloheximide led to superinduction. We observed no correlation between the effect of IPR on cell replication or organ growth and stimulation of c-fos expression, and conclude that the latter is the result of beta-adrenergic receptor-IPR interaction. The c-fos protein was localized immunocytochemically in both the cytoplasm and the nuclei of acinar cells and in the nuclei of duct cells.