In vitro study of antral gastrin biosynthesis in response to weaning and corticosterone acetate in rats.

The effects of weaning (abrupt dietary changes from breast milk to solid food) and corticosterone injection on antral gastrin-like immunoreactivity (G-LI) concentrations and antral G-LI biosynthesis were studied in rats. A single dose of corticosterone acetate was injected in one group of 7 days old rats, and a single dose of physiological saline was injected in another. Each group of rats was divided into two subgroups, one fed only rat breast milk until 25 days old and the other weaned at day 21. In non-corticosterone treated unweaned rats, antral G-LI did not increase. In non-corticosterone treated weaned rats, antral G-LI was constant before weaning, then increased 4-fold to the adult level. In corticosterone treated unweaned rats, the antral G-LI on day 11 was twice than on day 7, and thereafter remained constant. In corticosterone treated weaned rats, antral G-LI increased after corticosterone treatment and increased again after weaning to reach the adult level at day 25. Gel filtration of pulse-chase incubated antral samples with L-[methyl-3H]methionine from unweaned rats without corticosterone administration showed Vo, fraction 19 (Fr. 19) and gastrin-34 (G34) peaks, but no gastrin-17 (G17) peak after 60 min of chase incubation, but at 120 min of chase incubation a G17 peak was present; corticosterone-treated and/or weaned (solid food alone) rat samples showed Vo, Fr. 19, G34 and G17 peaks at 30 min of pulse incubation.