24-HOUR BASAL AND REPETITIVE PENTAGASTRIN-STIMULATED GASTRIC-ACID SECRETION IN NORMAL AND SHAM-OPERATED RATS AND IN RATS AFTER GONADECTOMY OR TREATMENT WITH ESTRADIOL OR TESTOSTERONE

Background: Studies in different species have suggested, but not estab lished, that sex hormones influence gastric acid secretion. We studied how acid output is affected by the sex hormones estradiol or testoste rone in vivo and in vitro. Methods: In gastric fistula rats that were normal, sham-operated, neonatally gonadectomized, or treated with estr adiol or testosterone, 24-h basal and pentagastrin-stimulated acid sec retion was measured. The in vitro effects of estradiol and testosteron e on histamine-induced aminopyrine accumulation in isolated parietal c ells were also determined. Results: Basal acid output was similar in t he two sexes, but stimulated secretion was significantly higher (34%; P < 0.01) in males. Ovariectomy did not influence acid output, whereas orchidectomy reduced basal (18%; NS) and stimulated 24-h secretion (P < 0.01). Estradiol decreased (23%; NS) the 24-h basal output in femal es but not in males. Estradiol suppressed stimulated secretion in fema les (29%, P < 0.01) and males (42%, P < 0.01) during the day. At night the stimulated secretion increased in both females (17%, NS) and male s (32%, P < 0.05). A similar pattern was found when rats were treated with testosterone. In vitro, estradiol and testosterone reduced histam ine-stimulated aminopyrine accumulation in both female and male isolat ed parietal cells. Conclusions: Estradiol and testosterone both appear to influence gastric secretion in rats, and their action differs betw een day and night, between the sexes, and between basal and stimulated secretion.