Impaired induction of cystatin S gene expression by isoproterenol in the submandibular gland of hypophysectomized rats

Cystatin S, an inhibitor of cysteine proteases, is produced and secreted by acinar cells of the rat submandibular gland. Expression of the cystatin S gene is known to be induced at high levels by the β-adrenergic agonist isoproterenol. In the present study, we revealed that in the submandibular gland of hypophysectomized adult male rats, the levels of induced cystatin S mRNA 24 h after a single administration of isoproterenol are strikingly lower than those in the gland of normal rats. Administration of one of the pituitary-dependent hormones testosterone, estradiol, dexamethasone and thyroxine, together with isoproterenol resulted in marked enhancement of the isoproterenol-induced cystatin S mRNA expression in hypophysectomized rats, whereas administration of any of these hormones alone had no significant effect. These results suggested the existence of cross-talk between the signaling pathways of steroid hormones and isoproterenol in inducing cystatin S gene expression in the rat submandibular gland.