Fetal and neonatal endocrine pancreas of the golden hamster (Mesocricetus auratus) was evaluated cytochemically with regard to maturation of beta cell granulation (aldehyde fuchsin technique) and the structural findings were related to the release of insulin-like activity (ILA) in vitro (rat epididymal fat pad bioassay).
In the fetal pancreas 12 hours before birth, beta cells could not be distinguished histochemically although considerable ILA was released. In the absence of distinct islands of Langerhans at birth, a few cells showed AF+ granulation which was accompanied by a slight increase in the ILA. Maximal release of ILA occurred approximately on the second postnatal day when the AF+ granulation was denser and more abundant than at earlier periods. Beyond the second day, the rate of in vitro ILA secretion decreased although islets and beta cells showed progressive structural maturation. There was also a relative increase in the amount of exocrine tissue in the portions of pancreas used for bioassay. Advancing proteolytic inactivation may have accounted for the decrease in effective ILA when the latter was expressed per unit weight of tissue.
The data indicate that in the golden hamster, beta cells are biochemically competent before they demonstrate cytochemical maturity.