Effects of somatostatin and acid on inhibition of gastrin release in newborn rats.

Newborn dogs, humans, and rats have elevated gastric luminal pH values and significantly elevated serum gastrin levels compared to adults. In the adult, acidification of the antral mucosa to pH 3.0 or lower inhibits gastrin release. Somatostatin is released by acid and may mediate this effect. We examined the effects of gastric acidification and somatostatin injection in rats aged 10 days to adult. Gastric gavage with 0.15 M HCl significantly lowered serum gastrin in animals of all ages. Somatostatin injection (400 micrograms/kg) significantly decreased serum gastrin in rats aged 18 days or older, but not in 10- and 15-day-old animals. These data indicate that 1) the mechanism whereby antral acidification inhibits gastrin release is at least partially developed in unweaned rats, 2) somatostatin is not a necessary mediator of the inhibition of gastrin release, and 3) at least part of the hypergastrinemia found in newborn animals is of antral origin.