In this study we investigated whether brain-gut peptides are implicated in the activation of the hypophysial-adrenal axis (HAA) in suckling rats treated orally with spermine.
The first group of rats received i.p. injections of bombesin, vasoactive intestinal polypeptide (VIP), somatostatin or neurotensin, starting on day 11 of life, and killed on day 14. The small intestine was removed and analysed for its content of proteins, DNA, polyamines and for its specific activity (SA) of disaccharidases. The second group of rats received one of the hormones cited above and was killed 45 min after the treatment for determination of corticosterone plasma concentration. Rats of the third group were adrenalectomised then treated with bombesin as the first group. The fourth group of rats was orally treated with spermine and sacrificed 2, 3, 4, 6 and 8 h thereafter for analysis of plasma and intestinal concentrations of bombesin.
The i.p. injection of bombesin increased the sucrase and maltase SA in the whole small intestine, while it decreased the lactase SA in the distal part. Intestinal weight and length, contents of DNA, protein, spermidine and spermine, and corticosterone plasma levels were enhanced by bombesin treatment. Somatostatin, neurotensin and VIP were ineffective on all the parameters studied. Adrenalectomy, in bombesin-treated rats, decreased the sucrase and maltase SA in the whole intestine, and decreased the lactase SA in the proximal intestine. It had no effect on intestinal weight and length, and protein content. Oral administration of spermine had no effect on plasma concentration of bombesin, whereas it decreased the content of this peptide in the whole small intestine.
It is possible that bombesin may control intestinal development in suckling rats and be a link between the ingestion of spermine and the liberation of corticosterone by the adrenal glands.