Effects of ovariectomy and hormone replacement on collagen and blood vessels of the urethral submucosa of rats

Collagen and blood vessels of the urethral submucosa of ovariectomized rats were studied following 28 daily subcutaneous injections of 17-β estradiol (n = 6, group 1), medroxy-progesterone acetate (n = 6, group 2), both drugs (n = 6, group 3) or vehicle (n = 6, control) and after sham surgery without castration or injection (n = 6). Investigations included the immunohistochemistry of estrogen and progesterone receptors and collagen fibres, Western blot analysis of collagen types I and III and counting periurethral vessels by light microscopy. Our results showed positive immunostaining with estrogen, progesterone and collagen types I and III in all samples. Collagen type I and III levels were lower in the controls than in the sham group. The other groups showed increases (2 > 3 > 1) over the controls with a relatively higher increase in type III. The type I/III collagen ratio progressively decreased (control > 1 > 2 > 3) below sham levels. The mean vessel count was significantly lower in control than in sham animals (P<0.00001). However, only estrogen treatment significantly increased the vessel number compared to controls (P = 0.04). Our results indicate that estrogen and progesterone, alone or in combination, have an effect on collagen types I and III, and that estrogen has an effect on blood vessels of the urethral submucosa in female rats.