The time of appearance and the pattern of localization of epidermal growth factor (EGF) in submandibular glands of mice was studied during postnatal development immunocytochemically. EGF was first detectable in the granular convoluted tubule (GCT) cells in the glands of males a t 20 days of age and of females a t 30 days of age. Development of GCT cells containing EGF was rapid in males, approaching adult conditions by 45 days of age. In females EGFcontaining GCTs developed more slowly and irregularly, and did not reach adult status by 45 days of age. It is concluded that EGF is restricted during postnatal development to the GCT cells, and that these cells and the distribution of EGF are represented dimorphically from their first appearance in the submandibular glands of both sexes.
Epidermal growth factor (EGF) is a potent biologically active polypeptide of known amino acid composition isolated from the adult mouse submandibular gland (Cohen, '62; Savage and Cohen, '72). In adult glands EGF is localized in the cells of the granular convoluted tubules (GCT) (Turkington et al., '71; Gresik and Barka, '77). However, the localization of EGF has not been reported in the developing submandibular glands, and this is described in the present study.