Hormonal Regulation of Epidermal Growth Factor and Protease in the Submandibular Gland of the Adult Mouse*

Abstract

The structure of the granular convoluted tubules of the mouse submandibular gland is influenced by androgens, adrenal steroids, and thyroid hormones. We wished to investigate the effects of variations in hormonal status on the quantitative and qualitative distribution of two secretory products of these tubules, epidermal growth factor (EGF) and protease. The effects of the thyroid and adrenal glands on EGF content and protease activity of the submandibular glands of adult female mice were studied by RIAs (EGF), enzyme assays (protease), and immunocytochemical methods. In animals rendered chronically hypothyroid by propylthiouracil (4 months) or in animals which were adrenalectomized and ovariectomized (3 weeks), protease activity and EGF levels were reduced by 81–97%. The administration of testosterone induced these polypeptides even in hypothyroid animals. Daily administration of L-T₄ (T₄; 1 μg/ g BW) for 7 days increased EGF and protease activity 3.6-fold in intact mice and reversed the effect of hypothyroidism. EGF and protease were also induced by T₄ in adrenalectomized and ovariectomized mice, although to a lesser degree than in intact animals. Immunocytochemical stainings of submandibular glands indicated that the number of granular convoluted tubule cells immunoreactive for EGF correlated with the levels of EGF determined by RIA_s. With respect to immunostaining for protease, such a correlation was not observed. The data indicate multihormonal regulation of EGF and protease in the mouse submandibular gland.