Objective. To study the effects of oestrogen and progesterone on submucosal collagen fibres and vascular plexus of the anal canal. Materials and methods. Experiments were performed on sections of the anal canal of ovariectomized rats following 28 daily subcutaneous injections of 17-β oestradiol (n = 6, OVX + E, Group 1), medroxyprogesterone acetate (n = 6, OVX + P, Group 2), both drugs (n = 6, OVX + E + P, Group 3) or vehicle (n = 6, OVX) and after sham surgery without castration or injection (n = 6). Investigations included immunohistochemistry of oestrogen and progesterone receptors and collagen fibres, Western blot analysis of collagen types I and III and counting of perianal vessels by light microscopy. Results. There was positive immunostaining for oestrogen and progesterone receptors in the mucosa and for collagen types I and III in the submucosa in all samples. Type I collagen levels increased significantly with ovariectomy but were normalized with treatment with oestrogen and progesterone. Type III collagen levels decreased after ovariectomy. Administration of oestrogen and progesterone appeared to restore level to near sham values. Semi-quantitative measurement of Type I/III collagen ratios by signal intensity demonstrated a very high ratio after ovariectomy. This appeared to be restored by both oestrogen and progesterone administration either individually or in combination. Mean vessel count was significantly lower in sham animals compared to values in OVX animals (P = 0.006). However, while only oestrogen treatment increased significantly the number of vessels compared to sham animals (P = 0.04), replacement with progesterone did not affect and in combination with oestrogcn reduced submucosal vessel number. Conclusion. Oestrogen and progesterone have synergistic effects on collagen types I and III and probably antagonistic effects on the vascular plexus of the anal canal submucosa in adult female rats.
- Faecal incontinence
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