Occurrence and neonatal development of N-terminal (1-15) immunoreactivity of big gastrin in the rat antrum.

G34N (1-15) immunoreactive cells and C-terminal tetrapeptide immunoreactive cells in the antrum of rats of various ages were studied immunocytochemically in both naturally weaned and non-weaned conditions. Some of the C-terminal immunoreactive cells were found to lack G34N (1-15) immunoreactivity while the remainder showed both types of immunoreactivity. G34N (1-15)/C-terminal immunoreactive cell rates increased with age and reached adult values at 3 weeks after birth. The rates in a non-weaned condition were, however, significantly lower than those in a naturally weaned rats. These findings suggest that the development of G34N (1-15) immunoreactivity in rat antral gastrin cells is closely related to maturation of the gastrin cells, and weaning may enhance the maturation process.