Oestrogen inhibits human colonic motility by a non-genomic cell membrane receptor-dependent mechanism

Background Classical effects of oestrogen involve activation of target genes after binding nuclear receptors. Oestrogenic effects too rapid for DNA transcription (non-genomic) are known to occur. The effect of oestrogen on colonic motility is unknown despite the prevalence of gastrointestinal symptoms in pregnant and premenopausal women. Methods Histologically normal colon was obtained from proximal resection margins of colorectal carcinoma specimens. Circular smooth muscle strips were microdissected and suspended in organ baths under 1 g of tension. After equilibration, they were exposed to 17β-oestradiol (n = 8) or bovine serum albumin (BSA)-conjugated 17β-oestradiol (n = 8). Fulvestrant, an oestrogen receptor antagonist, was added to some baths (n = 8). Other strips were exposed to calphostin C or cycloheximide. Carbachol was added in increasing concentrations and contractile activity was recorded isometrically. Results Oestrogen inhibited colonic contractility (mean difference 19·7 per cent; n = 8, P < 0·001). In keeping with non-genomic, rapid-onset steroid action, the effect was apparent within minutes and reversible. It was observed with both 17β-oestradiol and BSA-conjugated oestrogen, and was not altered by cycloheximide. Effects were inhibited by fulvestrant, suggesting receptor mediation. Conclusion Oestrogen decreases contractility in human colonic smooth muscle by a non-genomic mechanism involving cell membrane coupling.