Inductive effects of triiodothyronine or dihydrotestosterone on EGF in the submandibular glands of young, middle-aged, and old C57BL/6NNia female mice.

Effects of advancing age on responsiveness to triiodothyronine (T3) or dihydrotestosterone (DHT) by granular convoluted tubule (GCT) cells in submandibular glands were studied in C57BL/6NNia female mice of 4, 12, and 24 months of age. In untreated mice, absolute GCT volume and the frequency of cells strongly immunostained for EGF increased with age. Concentrations of EGF rose fourfold. Both T3 and DHT had inductive effects at each age: GCT cells were enlarged, contained more granules, and stained very strongly for EGF; EGF concentrations and the volume of GCTs also increased. However, the pattern of induction differed with age for the two hormones. After T3 treatment EGF concentration declined with age with respect to the degree of induction over same age control levels. By contrast, after DHT treatment the level of induction of EGF over control levels was the same at all three ages. The pattern of aging of GCT cells and their responsiveness to T3 or DHT in female mice differ from that previously reported for males.