Effects of hormones on differentiation of parotid glands of suckling mice in vitro.

The hormonal requirements for functional differentiation of mouse parotid glands were investigated using organ cultures in chemically defined medium. The hormones tested were insulin, thyroxine and prednisolone, and the parameters examined were alpha-amylase activity and the ultrastructure of the tissue. It is found that most of the amylase in the cultures (80%) was released into the culture medium after 5 days of cultivation. Prednisolone (5 . 10(-3) mg/ml) alone resulted in a 3--4-fold increase in specific activity of amylase (total amylase activity in the medium and culture) over that in its absence, but neither insulin nor thyroxine alone induced the enzyme. Prednisolone plus thyroxine (over 1 . 10(-7) mg/ml) or insulin (over 1 . 10(-3) unit/ml) induced markedly the enzyme, amylase specific activity being as much as 4- or 6-fold that with prednisolone alone. Moreover the enzyme specific activity was dependent on the prednisolone concentration (5 . 10(-7) - 5 . 10(-3) mg/ml) in the presence of thyroxine (1 . 10(-2) mg/ml) or insulin (1 . 10(-2) unit/ml). Morphological differentiation was also observed in explants cultivated in medium containing prednisolone plus thyroxine or insulin. These results suggest that besides glucocorticoids, insulin and thyroxine are involved in increase in amylase activity in mouse parotid glands during the late suckling period.