Role of sex hormones in gastrointestinal motility in pregnant and non-pregnant rats

Abstract

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.

Keywords: Gastric emptying; Gastrointestinal motility; Magnetic fields; Reproductive physiological process; Sex hormones.

Figure 1

Profile of gastric contractility signals and their respective Fourier transform obtained in female rats during the estrous cycle (estrous phase) and pregnancy (day 14). The frequency values obtained were 4.3 and 3.6 cpm (71.7 and 60.0 mHz), respectively.

Figure 2

Profile of gastric emptying and cecum arrival obtained in estrous cycle (estrous phase) and pregnancy (day 14). Arrows indicate the statistical moment (minutes in X-axis), and consequently, mean gastric emptying time and mean cecum arrival time for each example.

Figure 3

Associations among gastric emptying time (min), frequency of gastric contractions (mHz), and progesterone levels (ng/mL) in female rats during pregnancy and the estrous cycle. ^aP < 0.03, compared with control (day 0); ^bP < 0.002, compared with days 0 and 20; ^cP < 0.001, compared with day 14; ^dP < 0.001, compared with days 0 and 20; ^eP < 0.05, compared with proestrus; ^fP < 0.001 compared with estrous.