Published online Jul 7, 2016. doi: 10.3748/wjg.v22.i25.5761
Peer-review started: March 8, 2016
First decision: April 14, 2016
Revised: May 7, 2016
Accepted: June 2, 2016
Article in press: June 2, 2016
Published online: July 7, 2016
AIM: To correlate gastric contractility, gastrointestinal transit, and hormone levels in non-pregnant (estrous cycle) and pregnant rats using noninvasive techniques.
METHODS: Female rats (n = 23) were randomly divided into (1) non-pregnant, (contractility, n = 6; transit, n = 6); and (2) pregnant (contractility, n = 5; transit, n = 6). In each estrous cycle phase or at 0, 7, 14, and 20 d after the confirmation of pregnancy, gastrointestinal transit was recorded by AC biosusceptometry (ACB), and gastric contractility was recorded by ACB and electromyography. After each recording, blood samples were obtained for progesterone and estradiol determination.
RESULTS: In the estrous cycle, despite fluctuations of sex hormone levels, no significant changes in gastrointestinal motility were observed. Days 7 and 14 of pregnancy were characterized by significant changes in the frequency of contractions (3.90 ± 0.42 cpm and 3.60 ± 0.36 cpm vs 4.33 ± 0.25 cpm) and gastric emptying (168 ± 17 min and 165 ± 15 min vs 113 ± 15 min) compared with day 0. On these same days, progesterone levels significantly increased compared with control (54.23 ± 15.14 ng/mL and 129.96 ± 30.52 ng/mL vs 13.25 ± 6.31 ng/mL). On day 14, we observed the highest level of progesterone and the lowest level of estradiol compared with day 0 (44.3 ± 15.18 pg/mL vs 24.96 ± 5.96 pg/mL).
CONCLUSION: Gastrointestinal motility was unaffected by the estrous cycle. In our data, high progesterone and low estradiol levels can be associated with decreased contraction frequency and slow gastric emptying.
Core tip: In female rats, the estrous cycle and pregnancy appear to disturb gastrointestinal motility because of variations in hormone levels, although data are conflicting. In vivo gastrointestinal studies during pregnancy are limited by the lack of safe and reliable methods. AC biosusceptometry and electromyography are appropriate for recording motility while adhering to ethical standards. Sex hormone variations were not sufficient to disturb gastrointestinal motility during the estrous cycle. In our data, high progesterone and low estradiol levels can be associated with decreased contraction frequency and slow gastric emptying. These data were obtained in vivo using harmless techniques during several reproductive stages.