Development of acid secretory function in the rat stomach: sensitivity to secretagogues and corticosterone.

Gastric acid secretion was studied in anesthetized rats from day 6 of the postnatal period up to the time of weaning. Basal H+ secretion was detected from day 6 in the first group studied (2.4 +/- 0.2 muEq of H+/10 min/100 g of body weight, BW) and remained constant up to the time of weaning (day 18: 2.5 +/- 0.2 muEq of H+/10 min/100 g of body weight) except for the period between days 10 and 12, when it fell significantly (1.5 +/- 0.06 muEq H+/10 min/100 g of BW on day 12). Both histamine H2 receptor sensitivity and intracellular transduction mechanism activities were evaluated by studying the secretory responses to histamine, impromidine (an H2 receptor agonist), cimetidine (an H2 receptor antagonist), forskolin (a direct adenylate cyclase activator), and dibutyryl (db) cAMP (an analogue of cAMP, the intracellular messenger mediating the response to histamine). The effects of pentagastrin and carbachol were also determined. The secretory responses obtained on days 6, 8, and 18 were similar and represented about threefold increases over basal secretion for all the secretagogues used. After weaning on day 20, both the basal secretion and the response to secretagogues were significantly increased compared with those of unweaned animals. On day 12, the responses were always weaker than on both days 8 and 18. Injection of 1 mg/kg of corticosterone 21 acetate daily from day 8 resulted on day 12 in a basal secretion and a response to histamine equivalent to those measured in 18-day-old pups not injected.(ABSTRACT TRUNCATED AT 250 WORDS)