Published online Jan 21, 2017. doi: 10.3748/wjg.v23.i3.426
Peer-review started: July 1, 2016
First decision: August 8, 2016
Revised: October 5, 2016
Accepted: October 19, 2016
Article in press: October 19, 2016
Published online: January 21, 2017
To evaluate sex differences and the effects of oestrogen administration in rat gastric mucosal defence.
Sex differences in gastric mucus thickness and accumulation rate, absolute gastric mucosal blood flow using microspheres, the integrity of the gastric mucosal epithelium in response to a chemical irritant and the effects of oestrogen administration on relative gastric mucosal blood flow in an acute setting was assessed in an in vivo rat experimental model. Subsequently, sex differences in the distribution of oestrogen receptors and calcitonin gene related peptide in the gastric mucosa of animals exposed to oestrogen in the above experiments was evaluated using immunohistochemistry.
The absolute blood flow in the GI-tract was generally higher in males, but only significantly different in the corpus part of the stomach (1.12 ± 0.12 mL/min•g in males and 0.51 ± 0.03 mL/min•g in females) (P = 0.002). After removal of the loosely adherent mucus layer the thickness of the firmly adherent mucus layer in males and females was 79 ± 1 µm and 80 ± 3 µm respectively. After 60 min the mucus thickness increased to 113 ± 3 µm in males and 121 ± 3 µm in females with no statistically significant difference seen between the sexes. Following oestrogen administration (0.1 followed by 1 µg/kg•min), mean blood flow in the gastric mucosa decreased by 31% [68 ± 13 perfusion units (PFU)] in males which was significantly different compared to baseline (P = 0.02). In females however, mean blood flow remained largely unchanged with a 4% (5 ± 33 PFU) reduction. The permeability of the gastric mucosa increased to a higher level in females than in males (P = 0.01) after taurocholate challenge. However, the calculated mean clearance increase did not significantly differ between the sexes [0.1 ± 0.04 to 1.1 ± 0.1 mL/min•100 g in males and 0.4 ± 0.3 to 2.1 ± 0.3 mL/min•100 g in females (P = 0.065)]. There were no significant differences between 17β-Estradiol treated males (mean ratio of positive staining ± SEM) (0.06 ± 0.07) and females (0.11 ± 0.11) in the staining of ERα (P = 0.24). Also, there were no significant differences between 17β-Estradiol treated males (0.18 ± 0.21) and females (0.06 ± 0.12) in the staining of ERβ (P = 0.11). Finally, there were no significant differences between 17β-Estradiol treated males (0.04 ± 0.05) and females (0.11 ± 0.10) in the staining of CGRP (P = 0.14).
Gastric mucosal blood flow is higher in male than in female rats and is reduced in male rats by oestrogen administration.
Core tip: We report a sex difference in absolute gastric mucosal blood flow using an in vivo rat experimental model. Male rats had approximately twice as high blood flow in the gastric corpus mucosa compared to females. Moreover, relative gastric mucosal blood flow decreased during oestrogen administration in males but not in females and the permeability of the gastric mucosa increased to a higher level in females than in males after taurocholate challenge. However, mean clearance increase, mucus thickness and accumulation rate and the expression of ERα, ERβ or calcitonin gene related peptide in the gastric mucosa did not differ significantly between the sexes.