Cystatin S: Molecular biology and sympathetic innervation

Abstract

The ratsubmandibular glands (SMG) are innervated by both the sympathetic and the parasympathetic branches of the autonomic nervous system which, in turn,regulate the secretory functions of the glands. Parasympathetic innervation of rat SMG is present at birth, whereas sympathetic nerve fibers reach the glands by postnatal day 5. Isoproterenol (IPR), a fi-adrenoceptor agonist, induces hypertrophic and hyperplastic enlargements of rat salivary glands, and induces the expression of a number of genes, including cystatin S, a member of family 2 of the cysteine proteinase inhibitor superfamily. Cystatin S gene expression is tissue-and cell typespecific, occurs transiently during development, and is not observed in adult animals. Sympathetic denervation of adult SMG, achieved by removing the superior cervical ganglion, reduces the induction of the cystatin S gene by a single injection of IPR. In addition, recent data indicate that the j3receptors present early in the developing SMG are functional and are capable of responding to IPR by increasing the ex pression of the cystatin S gene, even when sympathetic nerve fibers have not reached the gland. The level of I PR-induced cystatin S mRNA remains constant until day 8, at which time a dramatic induction of cystatin S mRNA is observed. This