Age related changes in NGF, EGF and protease in the granular convoluted tubules of the mouse submandibular gland. A morphological and immunocytochemical study

Granular convoluted tubule (GCT) cells in the submandibular glands of male mice were studied at 1.5, 6, 12 and 29 months of age by morphometric and immunocytochemical means. The relative proportion of GCT's was established by determining a tubule to acini (T/A) ratio. The T/A ratios were significantly increased between 1.5 months (0.76) and 6 months (1.34), and between 6 months and 12 months (1.96). However, a marked decrease was found at 29 months (0.59). The functional capacity of GCT cells was estimated by immunocytochemical staining for nerve growth factor (NGF), epidermal growth factor (EGF), protease and renin. The number of GCT cells immunoreactive for NGF, EGF and protease increased between 1.5 months and 6 months. No further change was noted at 12 months. However, once again at 29 months a decrease occurred in a number of cells reactive for all three substances. Renin was not detected in any cell at any age.