Expression of the epidermal growth factor gene in mouse lachrymal gland: comparison with that in the submandibular gland and kidney.

Expression of the epidermal growth factor (EGF) gene in mouse lachrymal gland was studied. The lachrymal gland of adult male and female mice contained immunoreactive EGF at a concentration of 0.013 +/- 0.002 (S.E.M.) and 0.014 +/- 0.003 ng/mg wet tissue respectively. Northern blot analysis of RNA from the lachrymal gland revealed the presence of 4.1-4.3 kb preproEGF mRNA, which was smaller in size than the 4.7-4.8 kb preproEGF mRNA in the submandibular gland and kidney. There was no sex difference in the mRNA level in the lachrymal gland, whereas the mRNA levels in the submandibular gland and kidney of adult male mice were 42-fold higher and twofold lower respectively than those of female animals. Administration of testosterone propionate or L-thyroxine to female mice increased submandibular gland levels of preproEGF mRNA by 35-fold or 12-fold respectively, but caused no change in lachrymal gland levels of preproEGF mRNA. The level of mRNA in the kidney was decreased by administration of androgen to one-third of that in control animals. The mRNA in the lachrymal gland was detected as early as 2 weeks of age and thereafter it remained at a constant level throughout adulthood, while that in the submandibular gland increased greatly during the pubertal stage. These results indicate differential hormonal and developmental regulation of EGF gene expression in the lachrymal gland, submandibular gland and kidney.