Thyroid Hormones Precociously Increase Nerve Growth Factor Gene Expression in the Submandibular Gland of Neonatal Mice

The developmental regulation of the expression of nerve growth factor (NGF) was studied in the mouse submandibular gland (SMG). Having demonstrated that, in the neonatal mouse, maturation of the SMG can be accelerated by treatment with thyroid hormones, with the resulting induction in SMG content of NGF, studies were undertaken to further examine the locus of thyroid hormone action. Because of the sexual dimorphism of the SMG, both male and female neonatal mice were used. NGF messenger RNA levels were undetectable in SMGs from untreated immature mice, while hybridization to total RNA from T4-treated mice was easily observable for NGF complementary DNA. Treatment for 14 days compared to 7 days resulted in a 7-fold increase in SMG NGF mRNA levels. A signal was obtained in 21-day-old control mice using S1 nuclease protection analysis; T4 increased NGF mRNA levels by 100-fold in both male and female immature mice. Heteronuclear RNA levels were induced 20-fold by T4. No sex differences were readily observable....