Does earlier weaning accelerate the development of stomach hormone responses in rats?

Details

This experimental developmental study measured cAMP responses to secretin, pancreatic glucagon, and histamine in gastric glands from fetal rats at gestational day 20, postnatal rats at days 1–30, and adult rats at day 65. Stimulation of cAMP by these hormones was already detectable at gestational day 20. cAMP generation showed biphasic variations during the first days of life and at the onset of weaning, at day 20.

Moving weaning forward to day 14 triggered precocious maturation of the efficacy of the cAMP-generating systems responsive to secretin, glucagon, and histamine, without changing the hormones’ potencies.

Throughout development, the general characteristics of the receptor–cAMP systems studied—including potency and pharmacological or regulatory properties—were comparable to those found in adult rats.

At days 5, 20, and 65, vasoactive intestinal peptide and the peptide with N-terminal histidine and C-terminal isoleucine amide (PHI) were about 100 times less potent than secretin. The EC50 for secretin was 1.5 × 10⁻⁹ M.

Histamine’s action could be blocked by the competitive H2-receptor antagonist cimetidine, with 70–100% inhibition, and by the noncompetitive inhibitor somatostatin, with 37–62% inhibition.

The findings indicate that these regulatory hormones—secretin, glucagon(s), histamine, and somatostatin—might act directly on gastric glands and may modulate their biological activities from the neonatal period in rats. Those activities include metabolism, differentiation, proliferation, and exocrine and endocrine secretions.

The study emphasizes the important physiological role of weaning in the final maturation of cAMP-generating systems in rat gastric glands.