Concentrations of Epidermal Growth Factor, Nerve Growth Factor, and Submandibular Gland Renin in Male and Female Mouse Tissue and Fluids*

Abstract

The submandibular gland of the mouse contains a variety of hormone-like substances and enzymes, such as epidermal growth factor (EGF), nerve growth factor (NGF), and submandibular gland renin (SGR). Using specific RIAs for each of these proteins and a radioreceptor assay (RRA) for EGF, the present study was performed to examine the concentrations of these three proteins and the molecular size of EGF in the submandibular glands and biological fluids of normal male and female mice. Submandibular glands of male mice contained far more radioimmunoassayable EGF, NGF, and SGR than those of female mice (66-, 92-, and 30-fold, respectively). Male saliva also contained far higher concentrations of radioimmunoassayable EGF, NGF, and SGR than that of the female (38-, 56-, and 49- fold, respectively). Furthermore, the molar concentrations of these proteins appeared to be similar to one another in submandibular gland tissue and in saliva. In contrast, although high concentrations of radioimmunoassayable and radiorecept ssayable EGF were found in urine, there was no significant sex difference, and neither radioimmunoassayable NGF nor SGR were detectable in the urine of either sex. Milk contained smaller amounts of these three proteins than did saliva. Gel exclusion chromatography revealed that the major component of EGF in the glands and fluids had equal RIA and RRAactivities and was similar in molecular size to mouse EGF tandard (mol wt, 6045). A high molecular weight EGF wasobserved in the tissue extracts and urine and appeared, at least in tissue, to be EGF noncovalently bound to other proteins. These data confirm the sexual dimorphism of the submandibular gland of the normal mouse with respect to its content of EGF, NGF, and SGR and indicate that all three proteins aresecreted into saliva in concentrations reflecting their concentrations in the submandibular gland. The roughly equimolar concentrations of these proteins in the gland and saliva suggest that they may be derived from a common precursor whose synthesis is re ulated by a single gene