Development of gastrin synthesis and posttranslational processing mechanisms in rats

To examine the ontogeny of gastrin synthesis and posttranslational processing mechanisms, we utilized region-specific antisera to determine the factors that regulate the contents of gastrin and its precursors in the stomachs of developing rats. Gastrin content increased gradually from birth to a peak at 5 wk of age, after which there was a slight decrease to levels observed in mature animals. Unlike gastrin, glycine-extended precursors of gastrin (G-Gly) increased abruptly in the first day of life but thereafter increased at a steady state. Dexamethasone treatment and early weaning (at 11 days of age) rapidly increased gastrin content, whereas G-Gly content was decreased. On weaning animals to adult rat chow abruptly at an age (18 days) when the corticosteroid surge associated with the weaning process had already occurred, evidence for increases in both gastrin and G-Gly content were observed 7 days later. In contrast, administration of dexamethasone to 18-day-old rats enhanced gastrin content to a greater extent than G-Gly. These results suggest that the natural surge in corticosteroids associated with weaning may enhance gastrin amidation activity, whereas the concomitant dietary changes may exert a stimulatory effect of gastrin synthesis.